Prepared by:

Julio Arboleda-Flórez, MD, FRCP(C), DABFP, PHD Epidemiology,
Heather L. Holley, MA, PHD Epidemiology,
Annette Crisanti, MSc, PhD Epidemiology (Student)
Calgary World Health Organization Collaborating Centre for Research and Training in Mental Health

For:

Public Health Agency of Canada
Health Canada
1996

Our mission is to help the people of Canada maintain and improve their health. Health Canada

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Également disponible en français sous le titre
Maladie mentale et violence : un lien démontré ou un stéréotype?

© Minister of Supply and Services Canada 1996
ISBN 0-662-24073-1
Cat. No. H39-346/1996E

Canadian Cataloguing in Publication Data
Main entry under title:
Mental lllness and Violence: Proof or Stereotype?
Issued also in French under title:
Maladie mentale et violence : un lien démontré ou un stéréotype?
Includes bibliographical references.

ISBN 0-662-24073-1
Cat No. H39-346/1996E

1. Mental illness
2. Violence — Psychological aspects
I.     Arboleda-Flórez, J. (Julio), 1939-
II.   Canada. Public Health Agency of Canada
III.  Canada. Health Canada

RC480.53M46 1996              616.89         C96-980003-7

Table of Contents

•      Acknowledgements iii
•      Preface v
•      Executive Summary vii
• 1.  Introduction 1
  •              Study Mandate 1
  •              Target Audience for this Report   2
  •              Definition of Terms 2
  •              Serious Mental Illness 2
  •              Violence 2
  •              Search Strategy 3
  •              Critical review Strategy 4
  •              Organization of this Report 5
• 2. Summary of Key Findings 6
  •              Community-Based Studies 6
  •              General Population Samples 6
  •              Police-Citizens Encounters 7
  •              Studies of Psychiatric Patients 8
  •              Studies of Incarcerated Offenders 10
  •               Prevalence Studies10
  •              Analytical Studies of Mental Disorder and Violence 11
  •              Follow-up Studies of Offenders Released into the Community 12
•              Summary of Key Findings 14
• 3. Critical Review: Does Mental Illness Cause Violence? 16
  •              Control for Confounding Factors17
  •              Confounding by Definition18
  •              Possible Confounding Due to Psychiatric Medications18
  •              Selecting Subjects to Avoid Bias19
  •              Classification of Mental Illness and Violence (Information Bias)21
  •              What Comes First? Temporal Ordering of Factors 22
  •              Biological Plausibility 24
  •              Proof or Stereotype? 26
  •              Conclusions 29
  •              Potential Directions for Future Research30
• References31
• Appendix A: Annotated Bibliography 40
  •              Introduction 40
  •              Causality 40
  •              Community studies: Empirical Studies based on General Population Samples41
  •              Studies of Psychiatric Patients 51
  •              Studies based on Samples of Incacerated Offenders 86
  •              Other Empirical Studies of Interest 120
  •              Review Articles and Key Position Papers 126
•   Appendix B: Glossary of Terms143

Ackowledgements

The researchers gratefully acknowledge the contribution of members of the Advisory Committee to this project:

Ms. Bonnie Pape,
Director of Programs,
Canadian Mental Health Association,
National Office,
Toronto, Ontario.


Ms. Susan Hardie,
Former National Coordinator,
National Network for Mental Health,
Guelph, Ontario.


Mr. Jim Holman,
Board Member,
National Network for Mental Health,
Guelph, Ontario.


Ms. Ann Braden,
President,
Schizophrenia Society of Canada,
National Office,
Don Mills, Ontario.

Mr. Alexander Saunders,
Chief Executive Officer,
Canadian Psychiatric Association,
Ottawa, Ontario.


Mr. James MacLatchie,
Executive Director,
John Howard Society of Canada,
Ottawa, Ontario.


Ms. Carol Silcoff,
Research Consultant,
Mental Health Unit,
Health Care and Issues Division,
Systems for Health Directorate,
Public Health Agency of Canada,
Health Canada.


Ms. Stephanie Wilson,
Program Officer,
Mental Health Unit,
Health Care and Issues Division,
Systems for Health Directorate,
Public Health Agency of Canada,
Health Canada.

The advice provided by Mr. Bob Shearer and Ms. Nena Nera of the AIDS Care, Treatment and Support Unit of Health Canada is gratefully acknowledged. The assistance of Marnie M. Hamilton, BSc., Research Assistant, who provided technical and library support is also acknowledged.

Preface

The issue of a possible relationship between mental illness and violence is not new. However, it is being increasingly highlighted through, for example, the work of the Federal/Provincial/ Territorial Implementation Work Group on the High-Risk Violent Offender Task Force Recommendations. This issue has also received attention in the non-governmental sector. Mental health advocates have traditionally stated that persons with mental illnesses are no more likely to commit violent acts than are persons who are not mentally ill. However, recent research and sensationalization of reports in the media have suggested that this may not be true, and that a certain subgroup of the mentally ill may be more violent than persons who are not mentally ill.

To help shed light on this complex and controversial issue, a critical review of the literature was commissioned by the Public Health Agency of Canada of Health Canada. A report was prepared under contract by Dr. Julio Arboleda-Flórez, Dr. Heather Holley, and Ms. Annette Crisanti, of the Calgary World Health Organization Collaborating Centre for Research and Training in Mental Health. Funding for this project was provided by the AIDS Care, Treatment and Support Unit under the National AIDS Strategy of Health Canada.

This project was a collaborative effort, with representatives from the Canadian Mental Health Association, the Schizophrenia Society of Canada, the Canadian Psychiatric Association, the National Network for Mental Health, and the John Howard Society of Canada sitting on an advisory committee.

The report is organized into five chapters. Chapter 1 provides an introduction to the report, and includes definitions, and a description of search strategies. Chapter  2 summarizes the main findings from the literature according to three broad themes: community-based studies, studies of the mentally ill population, and studies of incarcerated offenders. Key statistical associations reported in the literature are described. Chapter 3 critically reviews the evidence relating mental illness to violence with the aim of determining whether the statistical associations reported in the literature meet the epidemiological criteria for causality. A listing of the references used in Chapter 3 is included. Two Appendices are also included: Appendix A contains an annotated bibliography of articles reviewed. Appendix B contains a brief glossary of key technical terms.

This report should be of value to any of the myriad of Canadian players who are involved in the mental health, social services, and criminal justice sectors, including service providers, policy-makers, programmers, researchers, consumers or family members.

A note on language:

Terminology used to refer to serious mental health problems and to persons with serious mental health problems in the report, such as “psychiatric patient”, reflect the terms used by the authors of the articles reviewed. For the sake of accuracy, the terms have not been altered, although it is recognized that more commonly used terms such as “consumers” or “survivors”, may be preferred by some readers.

Executive Summary

Introduction and Rationale:

Mental health advocates have traditionally stated that persons with mental illnesses are no more likely to commit violent acts than are persons who are not mentally ill. However, there has been growing uncertainty as to the exact nature of the relationship, among caregivers, health care providers, and advocacy groups, spawned, on the one hand, by sensational media accounts and television dramas, and on the other, by conflicting scientific reports. This complex issue has important consequences for persons with mental disorders and their families, health care and social service providers, policy makers, programmers, and persons in the criminal justice system. To help shed light on this issue, this critical review of the literature was undertaken.

Search Strategy:

Computerized databases covering the scientific literature in the areas of psychology, sociology, criminology, law, medicine, philosophy, psychiatry, forensic psychiatry, and epidemiology were searched for any articles dealing with mental illness and violence. In order to maintain a broad search strategy, a number of different synonyms were used for the terms ‘mental illness’ and ‘violence’ resulting in 32 different search combinations and capturing over 5,500 unique citations. These reflected some 8,000 authors, 8,600 key words, 940 journals, and spanned some 30 publication years.

The review focused on articles published in the last 10-15 years because these were considered to represent the bulk of studies pertinent to present day populations of the mentally ill. In order to make the results of this investigation useful to the widest possible audience, studies dealing with a variety of mental disorders were assessed including serious functional mental illnesses (such as schizophrenia or major depressive illnesses), substance abuse disorders (particularly alcohol abuse), and personality disorders (particularly antisocial personality disorder). To keep the review manageable, the definition of violence was restricted to acts involving physical assaults or threats to others, including violent criminal acts.

The report contains detailed abstracts of over 100 different articles pertaining to the relationship between mental illness and violence. Empirical studies are grouped according to a number of different topic areas, depending on main population of interest. These include (a) General Population Samples (b) Psychiatric Patients (c) Incarcerated Offenders (d) Other Empirical Studies of Interest, and (e) Reviews and Position Papers.

Critical Review Strategy:

Because of the stigma that could result from a premature and unproven statement purporting a causal relationship between mental illness and violence, this review adopted a rigorous and conservative scientific perspective that permits a judgement of causality only (a) in light of compelling confirmatory evidence from well designed and executed studies, and (b) given that no compelling disconfirmatory evidence exists.

An epidemiologic framework was used to make a judgement of causality. Epidemiology is concerned with the study of the occurrence of disease and health events in human populations and attempts to identify the factors that cause or influence these patterns. In the United States, courts of law have determined that statements of causality in human populations come most authoritatively from studies employing epidemiological criteria.

Epidemiologists adhere to a hierarchy of evidence placing the most credence in statistical associations demonstrated  in well-designed and executed cohort studies. These studies define subjects on the basis of the presence or absence of mental illness and follow two or more groups through time to compare outcomes. Case-control study designs that define subjects on the basis of outcome (e.g. presence or absence of violence) then collect retrospective data on the presence or absence of mental illness, can provide persuasive evidence but are usually not deemed to be sufficiently strong to make a causal judgement. Descriptive cross-sectional surveys are used to generate hypotheses for further testing. Because data on both mental illness and violence are collected simultaneously, it is difficult to ensure that the mental illness predated the violence, as would be required for a causal relationship. Therefore, results from surveys are not used to infer causality.

Summary of Key Findings:

Studies cited in this review are drawn primarily from Canadian and American sources. A caveat must be noted with respect to generalizability of findings from the United States, where much of the research has been conducted, to Canadian populations. Interpretation and application of findings to the Canadian context must be cautiously undertaken in view of differences in the health care and criminal justice systems of the two countries.

A number of statistical relationships were reported throughout the literature. These are summarized as follows:

• The strongest predictor of violence and criminality is past history of violence and criminality. This was true regardless of diagnostic group (e.g., whether schizophrenia or substance abuse).
• As yet, there is no consistent evidence to support the hypothesis that mental illness (e.g., depression) that is uncomplicated by substance abuse is a significant risk factor for violence or criminality, once past history of violence is controlled.
• Whether persons with schizophrenia are at risk of violence depends, in part, on the context and the presence of psychotic symptoms. For example, persons with schizophrenia have been found to be at somewhat increased risk of committing violent acts when in the community, especially when they are experiencing psychotic symptoms. Conversely, violent behaviour has been found to be low among hospitalized patients with schizophrenia who are receiving appropriate neuroleptic medication.
• The occurrence of violent incidents among persons hospitalized with a mental illness may be increasing. However, a small number of these persons, typically those with acute psychotic symptoms or dementia, or who have a history of prior violence, have usually been found to be responsible for the majority of violent incidents. Most violent incidents leading to hospitalization occur in the home, and involve episodes of damage to furniture or minor assaults to relatives.
• Formerly hospitalized mental patients may be at high risk of arrest and violence when released into  the community, particularly if they have a history of prior arrests or violence or if they experience psychotic symptoms;
• Family members (not the general public) are the most likely targets of violence from formerly hospitalized patients in the community;
• Substance abuse appears to be a significant risk factor for violence and criminality among community, hospitalized, and offender populations. It is unlikely that a member of the public would be at risk of violence from someone with a non-substance abuse disorder;
• Studies of police-citizen encounters in both Canada and the United States show that the pattern of criminality among persons with mental illness and persons without mental illness coming into contact with the police is similar. Persons with mental illnesses are no more likely to be charged with a violent crime compared to those persons who do not have a mental illness;
• The prevalence of substance abuse disorders and mental disorders is high among remanded and provincially incarcerated offenders. Yet, the overall rate of detection of mental illness by correctional staff appears to be quite low. Explanations for the high prevalence of mental illness among incarcerated offenders have included the “criminalization” of mentally disordered behaviour, the “psychiatrization” of criminal behaviour, and the pathogenic nature of incarcerated environments;
• In general, offenders’ post-release adjustment does not appear to be related to major mental illnesses (such as schizophrenia or depression) or substance abuse disorders when prior criminality and age are controlled; and
• Most generally, individuals who are younger are at higher risk of violence and criminality.
• 
  

Does Mental Illness Cause Violence?

A critical analysis of the literature reveals that as yet, there is no compelling scientific evidence to suggest that mental illness causes violence.

Studies of violence among the treated mentally ill population demonstrate that this population does have higher levels of criminality and violent criminality compared to the general population, and a high incidence of violence while in hospital. Similarly, studies of mental illness among incarcerated offenders have shown a high prevalence of serious mental disorders and substance abuse disorders. However, despite such clear demonstrations, these findings do not support the conclusion that mental illness causes violence for the following methodological reasons:

• It is not always clear how comparisons across study groups should be adjusted to take account of factors such as age, sex, socio-economic status, prior arrests, or prior institutionalizations. For example, many authors have used violent criminality as a measure of violence. However, it is known that the relationship between mental illness and violent criminality depends on whether  study groups are statistically comparable with respect to other characteristics that predict crime such as socio-economic status, age, or prior arrest histories. When study groups are comparable on these factors, the relationship between mental illness and violence often disappears. However, authors have dealt with these issues differently, depending on their understanding of the causal process underlying the relationship between mental illness and violence and as yet, no study has appropriately dealt with all of these factors. Therefore, it is difficult to draw firm causal conclusions.
• Using current psychiatric diagnostic conventions, it is not possible to diagnose mental illness independently from violence. Almost half of the disorders described in the North American standard Diagnostic and Statistical Manual for Mental Disorders, Third Edition, Revised (DSM-III-R) (American Psychiatric Association, 1987) are described or defined in part on the basis of violent behaviours and similar criteria are used in the more recent DSM-IV (American Psychiatric Association, 1994). These include schizophrenia, bipolar disorder, substance abuse, and some personality disorders. Over time, our concept of mental disorder has changed to incorporate more criteria pertaining to violence. Therefore, it is likely that the more recent studies that show a statistical relationship between mental disorder and violence are an artifact of the way we have come to define and measure these conditions.
• A number of commonly used psychiatric medications (including tranquilizers/ sedatives) have been reported to cause aggression. It is not known to what extent such paradoxical reactions could account for violence among the mentally ill receiving short and long-term psychopharmacological treatments.
• Virtually all studies conducted to date have based their results on treated populations of persons with mental illness or incarcerated offenders. These groups are not representative of all persons with mental illnesses. These studies are biased toward those sub-populations of persons with mental illness who are more prone to violence. Current civil committal legislation, which is based on a standard of dangerousness, ensures that persons who are dangerous to themselves or to others are admitted to hospital. If persons do not meet the more stringent committal criteria and refuse hospitalization, they may be arrested in order to access mental health services through correctional routes. Because of these selection pressures, results based on treated populations will lead to exaggerated estimates of the relationship between mental illness and violence.
• Many studies have relied on institutional records (such as admissions to a psychiatric facility or arrests) to classify their subjects. Clearly, institutional records do not correctly classify all persons with a mental illness or all persons who have committed a violent act. Too often, official statistics reflect political biases and  social trends and this interferes with the appropriate interpretation of the data.
• Primary data collected from general population samples have the greatest potential to produce valid results bearing on the issue of mental illness and violence. To date, however, only two studies in the general population have been conducted—one in the United States and one in (Alberta) Canada. Both used state-of-the-art epidemiological survey techniques and representative samples of the general population. Both studies used a structured diagnostic interview schedule for DSM-III-R diagnoses to define mental disorders. Items referring to violent behaviour used to derive these psychiatric classifications were then used to define violence. While both studies report a statistical relationship, it is not clear whether this could be explained by the lack of independence in the way mental illness and violence were defined. Secondly, neither study was able to establish temporal ordering of factors; a crucial omission. Therefore, it is not clear whether the violence preceded the mental illness, or vice versa. Only when mental illness precedes violence can a causal interpretation be made.
• 
  

Potential Directions for Future Research:

We are not yet at the stage where it is possible to make a valid causal judgement about the relationship between mental illness and violence. Yet, based on our current knowledge from biochemical and genetic studies, a link between these two remains biologically plausible.

Several methodological challenges lay ahead for future research. Perhaps most importantly, we must develop independent measures of mental illness and violence. The DSM standard psychiatric nosology has limited application in this area given that almost half of the disorders are described or defined in part on the basis of violent acts. Secondly, researchers must move out of institutions to measure the relationship of mental illness and violence in unselected or representative samples. Finally, longitudinal follow-up designs which permit clear temporal ordering of factors and appropriate treatments for factors such as age, sex, socio-economic status, and prior violence must become the gold standard. Until such studies are completed, there can be no scientific basis for concluding that mental illness causes violence.

The paucity of published literature incorporating the perspective of those who have a mental illness should also be addressed. The views and experiences of consumers and their family members would contribute further to the examination of violence as it is experienced by these individuals in community and hospital settings, and among peers. This is an area where future work is needed.

While not the subject of the current review, the research reviewed in this study raises questions in regard to the extent to which the following issues are being addressed:

• Appropriate identification of mental illness and substance abuse problems among incarcerated offenders in correctional settings.
• Management of disturbed behaviour by the mentally ill that is often directed towards family members. Such approaches are being used in hospital settings.
• Appropriate access to community resources for former mental patients in the community.
• Appropriateness of treatment for the mentally ill in correctional and community settings.

1 Introduction

Study Mandate:

Objective and systematic study of the relationship between mental illness and dangerousness is crucial to the formulation of appropriate and effective policies for the provision of mental health services (Davis, 1991). This is true regardless of whether the service is required in the community, within the mental health system, or within correctional settings. Evidence supporting a relationship between mental illness and violence is also pivotal in the debate concerning the appropriate use of involuntary hospitalization, the design of community-based controls for violence among persons with mental illness (Mulvey, 1994), and the utilitarian need to understand the social consequences of deinstitutionalization policies (Mulvey, Blumstein, and Cohen, 1986).

In the post-deinstitutionalization era, negative community attitudes and fears, fostered in part by selective media reporting, have surfaced as the most persistent obstacle to the fulfilment of community-based treatment goals (Rabkin, 1979; Steadman, 1981). In addition, current health restructuring, which is occurring in all parts of Canada, will place unprecedented pressure on general hospital psychiatric programs and psychiatric facilities to transfer persons with mental illness to the community and to drastically curtail subsequent lengths of stay and even access for acute treatment.

While the claim that the mentally ill are violent has been traditionally opposed by mental health advocates and researchers (e.g. Monahan and Steadman, 1983), recent literature reviews written by prominent researchers in the field (e.g. Monahan 1993; Torrey, 1994) now suggest that mental illness may be causally connected to violence, particularly for certain sub-groups of the mentally ill. Faced with a second major wave of dehospitalization, and renewed scientific controversy, it is an opportune time to re-ask the question: is there compelling scientific evidence to support a causal understanding of the relationship between mental illness and violence?

The following critical appraisal of the literature was commissioned by the Public Health Agency of Canada of Health Canada. An advisory committee guided this project and was composed of representatives from the Mental Health Unit of Health Canada, the Canadian Mental Health Association, the Canadian Psychiatric Association, the John Howard Society of Canada, the National Network for Mental Health, and the Schizophrenia Society of Canada. The critical appraisal of the literature was conducted by psychiatric epidemiologists from the Calgary World Health Organization Centre for Research and Training in Mental Health in Alberta, Canada. This work complements a meta-analytic study focused on predictors of recidivism among the mentally disordered offender population underway at the Solicitor General of Canada. Findings should be available within the coming months.

Target Audience for this Report:

While the issues addressed by this report are of interest to mental health providers, persons with mental illness, and their families, and while every effort has been made to avoid unnecessary jargon, this report may be more readable by persons with some familiarity with scientific concepts. A glossary of terms (Appendix B) has been included to assist non-technical readers in understanding the use of key terms and a non-technical companion report is currently under development.

Definition of Terms:

• Serious Mental Illness:

In order to make the results of this investigation useful to the widest possible audience, studies dealing with a variety of mental disorders were assessed including conditions such as schizophrenia, major depressive illnesses, substance abuse disorders, and personality disorders. The bulk of the literature reviewed relied on Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM-III-R) as the standard diagnostic nosology (American Psychiatric Association, 1987). However, studies were not excluded from review if they used earlier versions of this nosology or another nosology.

A number of key words were used when conducting the computerized search to capture articles studying violence among the seriously mentally ill. These included:

• Mental disorder
• Mental illness
• Mentally ill offenders
• Psychiatric patients
  

Violence:

The term ‘violence’ was used quite loosely throughout the literature to refer to a wide range of behaviours including acts involving physical assault, physical threats, verbal threats, psychological or emotional abuse, damage to property, suicide, and self-harm. This review focuses on violence toward others, as opposed to violence expressed toward the self. Violence toward others was broadly conceptualized to reflect behaviours of persons against others that were meant to intentionally threaten or actually inflict physical harm. Many researchers measured violence with reference to criminal acts involving arrests or convictions for violent crime.

We considered a definition that restricted ‘violence’ to interpersonal physical acts to be appropriate for a number of reasons. First, if there is a causal relationship between mental illness and violence, it should be most easily detected in its most extreme manifestations. Second, the occurrence of physical violence can be determined more reliably, therefore, is likely to be more consistently defined and reported from study to study.

Synonyms for violence used in conducting the search strategy included:

• Violence
• Aggression
• Dangerous
• Violent behaviour
• Assault
• Crime
• Criminality
• Battery
• 
  

Search Strategy:

Peer-reviewed articles published over the last 10-15 years were the main target for review because these represent the bulk of studies pertinent to present day populations of persons with mental illness. Exceptions to this rule were made for particularly interesting, informative, or “classic” studies. Similarly, while our main emphasis was on reviewing quantitative empirical studies, key qualitative studies and literature reviews were also included.

The search for appropriate material began with a structured investigation of four computerized databases (PsychLit, Index Medicus, Sociofile, and the Calgary WHO Collaborating Centre Forensic Holdings) representing peer-reviewed literature from psychology, sociology, law, criminology, medicine, philosophy, psychiatry, forensic psychiatry, and epidemiology. The critical analysis was restricted to peer-reviewed journals as these are known to meet minimum standards for scientific validity. Articles were reviewed in English, French, and Spanish. Non-English articles that were considered appropriate for inclusion in the annotated bibliography have been annotated in English. Also, because computerized bibliographic systems have been shown to miss many pertinent articles (e.g. Adams, Power, Frederick, and Lefebvre, 1994), relevant publications were also sought from the reference lists of articles that were reviewed.

The various key words for mental illness and violence (described above) resulted in a maximum of 32 different search combinations per database. As the search progressed and we became familiar with the most productive key words, it was possible to progressively narrow the search strategy. For example, it became clear after the first search that the term “battery” was used largely to refer to psychological test batteries. This term was dropped from subsequent searches. Some databases (such as Index Medicus) used fewer synonyms for mental illness and criminality so this reduced the number of search combinations.

Over 5,500 unique citations were captured from the computerized searches using the keyword combinations. These reflected some 8,000 authors, 8,600 key words, 940 journals, and spanned some 30 publication years. In order to manage this volume of material, complete references and all available abstract data were electronically downloaded to a desk-top computer-based system equipped with specialized software for further processing. This software proved  indispensable in identifying and eliminating duplicate references that appeared in more than one library database, and for creating lists.

A listing of citations and complete study abstracts was produced for the first level of critical review. So as not to overlook relevant citations, this list was reviewed independently by two members of the research team. Copies of articles were then retrieved from the library for more detailed critical review. Local library holdings provided access to the major North American and European journals. Inter-library loans provided access to the less accessible publications.

Of the original 5,500 citations, some 400 articles were retrieved from the library and reviewed in detail using standard epidemiological criteria. Those included in the annotated bibliography are based on our best judgement that they constitute the key publications in the area.

Critical Review Strategy:

Because of the stigma that could result from a premature and unproven statement purporting a causal relationship between mental illness and violence, this review has adopted a rigorous and conservative scientific perspective that permits a judgement of causality only (a) in light of compelling confirmatory evidence from well-designed and executed studies, and (b) given that no compelling disconfirmatory evidence exists.

An epidemiological framework was used to make a judgement of causality. Epidemiology is concerned with the occurrence of disease and health events in human populations and attempts to identify the factors that cause or influence these patterns (Lilienfeld and Stolley, 1994). In the United States, courts of law have determined that statements of causality in human populations come most authoritatively from studies employing epidemiological criteria (e.g. Brock v. Merrell Dow Pharmaceuticals, 1989; Daubert v. Merrell Dow Pharmaceuticals, Inc., 1993).

Epidemiologists adhere to a hierarchy of evidence placing the most credence in statistical associations demonstrated in well-designed and executed cohort studies. These studies define subjects on the basis of the presence or absence of mental illness and follow two or more groups through time to compare outcomes. Case-control study designs that define subjects on the basis of outcome (e.g. presence or absence of violence) then collect retrospective data on the presence or absence of mental illness, can provide persuasive evidence but are usually not deemed to be sufficiently strong to make a causal judgement. Descriptive cross-sectional surveys are used to generate hypotheses for further testing. Because data on both mental illness and violence are collected simultaneously, it is difficult to ensure that the mental illness predated the violence, as would be required for a causal relationship. Therefore, results from surveys are not used to infer causality.

Organization of this Report:

This report is organized into three main sections. Chapter  2 summarizes the main findings from the literature according to three broad themes: community-based studies, studies of the mentally ill population, and studies of incarcerated offenders. The aim of this chapter is to describe the key statistical associations that have been reported in the literature. Statistical associations that are strong and appear consistently across different types of studies conducted in different locations are considered to be most noteworthy. Chapter 3 critically reviews the evidence relating mental illness to violence with the aim of understanding whether the statistical associations reported in the literature meet the epidemiological criteria for causality. A listing of the references used in Chapter 3 is also included. Appendix A presents the annotated bibliography of articles used in this report. These are organized according to themes: main population of interest (community studies, studies of psychiatric patients, and studies of incarcerated offender populations), other empirical studies of interest, and review articles. Within each broad theme, articles are organized alphabetically, according to author and title. To assist the non-scientific reader in drawing pertinent comparisons across articles, all empirical studies have been critically reviewed and summarized according to a standardized abstract structure: (a) purpose and objective, (b) research design, (c) study setting, (d) study subjects, (e) measures used, (f) main findings, (g) conclusions, (h) methodological critique, and (i) causality. Appendix B contains a brief glossary of key technical terms.

2    Summary of Key Findings

Researchers have approached the study of mental illness and violence from a number of different perspectives depending on their access to community, mental health, or criminal justice populations. This has resulted in a large body of research. The first goal will be to summarize the results of these studies in order to understand the statistical associations between mental illness and violence which have been reported in these various populations. The second goal, addressed in the next chapter, will be to critically evaluate to what extent these findings can be used to support an etiologic (i.e. causal) relationship between mental illness and violence.

Community-Based Studies:

• General Population Samples:

Two studies have conducted population surveys of representative samples of adults living in the community—one Canadian, studying 1,200 Edmontonians (Bland and Orn, 1986), and one American, studying 10,059 subjects from three of the five Epidemiological Catchment Area sites (Swanson, Holzer, Ganju, and Jono, 1990). Both studies use what has come to be known as the ‘ECA Methodology’. This methodology characterizes the Epidemiological Catchment Area Surveys conducted in five sites in the United States.  Currently considered to be state-of-the-art in psychiatric epidemiologic surveys, the ECA approach employs large and representative samples, a structured diagnostic interview administered by lay interviewers (The Diagnostic Interview Schedule or DIS), and computer scoring of the results to arrive at standardized DSM-III-R diagnostic categories. Both studies used questions from the DIS to measure physical violence, such as hitting or throwing things at a spouse or partner, spanking or hitting a child, fist fighting since age 18 with someone other than a spouse, using a weapon since age 18, and getting into a physical fight while drinking.

Both studies report statistical associations between violence and mental disorders, although neither study is able to disentangle the temporal ordering of factors. In Canada, three diagnostic categories were studied: antisocial personality disorder, major depression, and alcohol abuse/drug dependence. Altogether, 54.5% of those with a diagnosis were involved in violent behaviour compared to 15.5% of those with no diagnosis. Persons with one or more of these diagnoses were almost seven times more likely to be involved in violence than those without one of these disorders. In particular, the risk of violence was greatly elevated among those diagnosed with a comorbid alcohol abuse disorder. When alcohol was combined with antisocial personality and/or depression, 80-93% were involved in violence. In the United States of America, more than half of the individuals reporting violent behaviour in the preceding year met the criteria for a psychiatric disorder compared to 19.6% of non-violent respondents. The highest percentages of violence were reported among substance abusers, ranging from 19.2% to 34.7% depending on the type of substance abuse. Individuals in the community meeting the criteria for any psychiatric disorder were more likely to engage in assaultive and violent acts compared to those who did not meet the criteria for a psychiatric disorder. However, certain diagnostic categories, such as non-comorbid anxiety disorder, affective disorder, or schizophrenia showed no or only slightly elevated risk of violence. Conversely, those with substance abuse disorders were at greatly elevated risk and also appeared to commit more severe acts of violence. These findings indicate that the public’s fear of persons with schizophrenia living in the community is largely unwarranted, although not entirely groundless. Citizens are more likely to be assaulted by someone suffering from a substance abuse disorder than a major mental illness such as schizophrenia.

Both studies suggest that individuals are at greater risk of being assaulted by someone who abuses substances rather than someone who is suffering from major mental illness such as affective disorder, anxiety disorder, or schizophrenia. Using the same ECA data, Swanson (1993) further tested the hypothesis that the relationship between mental disorder and violence could be largely explained by the association between alcohol abuse and violence. Mental illnesses that were uncomplicated by alcohol abuse were associated with some increased risk of violence. However, the apparent large increase in violence among younger, lower socio-economic males was found to be largely due to the increased prevalence of alcohol abuse and comorbidity in this group. A history of arrest and psychiatric hospitalization was found to be associated with an increased probability that a person would be violent.

• Police-Citizen Encounters:

Police have considerable discretionary powers in responding to persons with mental illness who may be acting in a disordered or disorderly fashion while in the community. The police may convey an individual to a psychiatric facility for assessment and treatment, or they may proceed with an arrest. Monahan, Caldeira, and Friedlander (1979) have shown that in 30% of police-initiated commitments, the police could have proceeded with an arrest. They did not because they believed that the individual lacked criminal intent or would benefit from treatment. Deinstitutionalization and legislative changes have increased the central role of the police in responding to persons with mental illness who come into contact with the criminal justice system. Bonovitz and Bonovitz (1981) show that the number of mental illness-related incidents handled by police increased over 200% between 1975 and 1979 after legislative changes permitted officers to expedite the removal of individuals with mental illness from the community. Teplin (1985) observed a random selection of 283 police officers in their day-to-day interactions with the public. A symptom checklist was used to assess the presence and severity of psychiatric impairment among those coming into contact with the police. Police encounters with individiuals with a mental disorder occurred infrequently (in 4% of 2,122 persons encountered). Persons with a mental disorder were only slightly more likely than persons without a mental disorder to be considered suspects in crimes, and for those who were considered to be suspects, the type of crime was not found to be related to the presence or absence of mental disorder. Those with a mental disorder did not commit serious crimes at a rate that was disproportionate to their numbers. The pattern of crime among mentally ill suspects was substantially similar to non-mentally ill suspects.

Similar findings are reported by Arboleda-Flórez and Holley (1988) who studied police-citizen encounters in Calgary, Canada. This study involved 350 persons who came into contact with police during a two-week period. Police rated the observable behaviour of these individuals on a continuum from normal to severely abnormal. The circumstances under which the encounters occurred were taken into account. The police officers were then asked to provide some judgement as to the cause of the abnormal behaviour: alcohol, drugs, mental illness, or other. Those persons identified by police as having a mental illness did not record a greater number of crimes against persons,  property, or other crimes compared to those identified as non-mentally ill.

Studies of Psychiatric Patients:

Physical violence in hospital has been reported in approximately 20% of samples studied (e.g. Lagos, Perimutter, and Saexinger, 1977; Binder, McNeil, and Binder, 1988). Typically, a small number of patients (e.g. 5%) are found to be responsible for just over half of all violent incidents and more than half of the serious injuries (Convit, Isay, Otis, and Volavka, 1990; Fottrell, 1980). Patients with psychotic symptoms, particularly paranoia, have been found to be at higher risk of physical aggression toward others (Noble and Rodger, 1989; Kennedy, 1993; McNeil and Binder, 1994). Among psychogeriatric patients, dementia has been shown to be related to aggressive and violent behaviour (Patel and Hope, 1992). Studying an outpatient psychiatric population, Tardiff and Koenigsberg (1985) report that 5% of subjects had been physically assaultive toward others in the few days prior to the evaluations and family members accounted for over half of those assaulted. Assaultive behaviour was associated with being male, younger than 20 years of age, and having a diagnosis of childhood or adolescent disorders or mental retardation.

Straznickas, McNiel, and Binder (1993), found that 19% of patients (113 of 581) in a university- based, locked, short-term psychiatric inpatient unit had physically attacked someone in the two weeks prior to their admission, and thirty-one of those patients who were assaultive attacked more than one person. Of the 113 patients who attacked someone, 50 assaulted people outside of the family, 10 patients assaulted both family members and individuals outside of the family, and 53 assaulted family members. Unfortunately, no comparison groups were used. Therefore, it is not clear whether the relatives of persons with a mental illness were more likely to be the targets of violence compared to the relatives of non-mentally ill.

Violence and fear-inducing behaviour have been found to be characteristic of the acute exacerbations of chronic conditions such as schizophrenia or mania which lead to a hospitalization. Binder et al. (1988) found that 21% of randomly selected inpatients (N=150) in a university psychiatric unit had attacked persons and 25% had engaged in fear-inducing behaviour in the two weeks just prior to their admission. This was especially true for patients suffering from schizophrenia or mania. In addition 13% of patients attacked others during their admission and 32% engaged in fear-inducing behaviour. Patients with a diagnosis of mania were more likely to attack others while those with a diagnosis of schizophrenia were more likely to engage in fear-inducing behaviour. These findings highlight  the importance of context as a factor influencing the expression of violent behaviours.

There is some evidence to suggest that the rate of violence among inpatients may be increasing. For example, Noble and Rodger (1989) report an increase in violent incidents occurring in hospitals between 1976 and 1984. Similarly, Volavka et al. (1995) report an increasing trend in the prevalence of arrests of psychiatric patients for incidents committed while in hospital.

A number of studies have examined the relationship of specific diagnoses to violence within populations of psychiatric inpatients. The major issue addressed by this avenue of research is what kinds of mental illnesses predict violence and criminality among mentally ill populations, not whether mental illness, per se, predicts criminality and violence.

Perhaps the most consistent and striking finding is the association of substance abuse disorders (alcohol and/or drug) with violence and criminality, and the lack of or small association between other disorders (e.g. schizophrenia, affective disorders, or anxiety disorders) with violence. As early as 1974, Guze, Woodruff, and Clayton demonstrated that felony convictions were reported by patients with diagnoses of sociopathic personality disorder and substance abuse leading the authors to conclude that sociopathy, alcoholism, and drug-dependence were the principle psychiatric disorders associated with serious crime. Similar findings are reported in more recent studies (Holcomb and Ahr, 1988; Modestin and Ammann, 1995).

The importance of substance abuse as a predictor of violence was found to hold even when studies were restricted to a single diagnostic group, such as patients with schizophrenia. For example, Cuffel, Shuway, Choulijian, and MacDonald (1994) studied only patients who had been diagnosed with schizophrenia to determine whether a comorbid substance abuse diagnosis increased risk of subsequent violence. Data were gathered from a retrospective record review of 103 outpatients who had been involved for six months in randomized clinical trials at a schizophrenia research clinic in San Francicso, United States. Violent behaviour included both property damage and acts against persons such as verbal threats to harm others, nonverbal threats to harm others, physical assaults, altercations, brandishment of weapons, using a weapon, starting a fire, or destroying property. Patients who were polysubstance abusers (alcohol and drugs) were significantly more likely to commit a violent act, although the risk diminished considerably three months into the study. These findings are consistent with the findings showing a statistical relationship between substance abuse disorders and violence in representative samples of adults.

A second interesting finding from this body of research has been the importance of prior violence and criminality in predicting subsequent violence and criminality (e.g. Asnis,  Kaplan, van Praag, and Sanderson, 1994; Klassen and O’Connor, 1988a, 1988b; Lundy, Pfohl, and Kuperman, 1993). This relationship is important in light of the significant percentage of mentally ill patients who report prior criminal and violent acts (e.g. Grossman, Haywood, Cavanaugh, Davis, and Lewis, 1995; Holcomb and Ahr, 1988).

Cirincione, Steadman, Clark-Robbins, and Monahan (1992) assessed the extent to which a diagnosis of schizophrenia was predictive of criminal violence, after controlling the effects of arrest history, among two cohorts of patients admitted to a New York State facility, one in 1968 (N=255) and the other in 1978 (N=327). The New York State Division of Criminal Justice Services provided data on violent crimes committed for the 11 years following the index psychiatric admission. Violent crimes included murder, manslaughter, rape, attempted rape, assault, kidnapping, and sodomy. Prior arrest history significantly correlated with violent crime in both cohorts. In 1968, diagnosis was a significant predictor of violent crime. However, this was not the case for the 1978 cohort. For those without a prior arrest, diagnosis did not predict subsequent violent crime. Similarly, Wessely, Castle, Douglas, and Taylor (1994) demonstrated a small increased risk of criminality among those with schizophrenia, but this was overshadowed by the much larger effects of prior criminality and substance abuse.

Buckley et al., (1990) provide information on the likely target of violence. They studied 698 patients who were diagnosed with schizophrenia and admitted to a psychiatric inpatient department in Dublin, Ireland between 1983 and 1988. Sixteen percent of patients had engaged in a physically violent or destructive act (i.e. to property) since the onset of their illness. Patients with no history of violence were found to be similar to those with a history of violence with respect to positive and negative symptomatology, and a family history of psychiatric illness. Violence was more common among males. Most of the incidents of community violence occurred in the home and involved episodes of damage to furniture or minor assaults to relatives.

Studies of Incarcerated Offenders:

• Prevalence Studies:

A number of studies have assessed the prevalence of mental illness among samples of incarcerated offenders. Interpreted within the broad context of criminalization of the mentally ill, these studies have been cited to support the hypothesis that large numbers of the mentally ill have been diverted from mental health to criminal justice systems. However, it is not clear from these studies what proportion of the mental illnesses reported predated the criminal behaviour (e.g., Allodi and Montgomery, 1975) or what proportion is a result of the “psychiatrization” of criminality (e.g., Davis, 1992).

Two large Canadian studies (Arboleda-Flórez, 1994; Bland, Newman, Dyck, and Orn, 1990)  provide compelling evidence that a significant proportion of incarcerated persons suffer from substance abuse disorders and serious mental illness. Although different methods of measuring mental disorder were used, both studies reveal consistent results. In the most recent study (Arboleda-Flórez, 1994), forensic psychiatrists conducted structured clinical interviews of a randomly selected sample of 1,200 admissions to the Calgary Remand Centre. Subjects were examined during the first 24 hours of detention. A principal diagnosis on either Axis I or Axis II of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R) was made in 728 of the 1200 interviewees (60.7%). The one-month prevalence was 49.5% for females and 56% for males for an Axis I disorder and 3.6% for females and 5.5% for males for an Axis II personality disorder. Substance abuse disorders occurred in 35.7% of women and 47.3% of men. Schizophrenia was not found among women (but this may have been due to their smaller numbers in the sample) and occurred in 1.2% of the males. Similarly, Bland, Newman, Dyck, and Orn (1990) studied a smaller, systematic sample of 180 males in custody at the Edmonton Remand Centre. The sample included remanded offenders and provincially sentenced prisoners (i.e. sentenced to two years less one day). Using the Diagnostic Interview Schedule (DIS) for lay interviewers, these authors found a lifetime prevalence of any psychiatric disorder of 92%. The most frequently occurring diagnosis was substance abuse (87%). Antisocial personality disorder occurred in 57%, affective disorder in 23% and schizophrenia in 2% of cases. The larger proportion of personality disorders identified in this study may be a function of the DIS which uses information about criminality in the diagnostic criteria. Studies showing a high prevalence of substance abusers among incarcerated offenders also have been reported in the United States (Barton, 1982; Lamb and Grant, 1982) and the United Kingdom (Taylor and Gunn, 1984).

Despite the high prevalence of mental disorder among incarcerated offenders, Teplin (1990) has shown that the overall rate of detection by prison personnel may be very low, with only 32.5% of personnel indicating poor provision of treatment for mentally disordered offenders. Persons are most likely to be identified for treatment if they had a prior treatment history (91.7% detected).

• Analytic Studies of Mental Disorder and Violence:

A number of studies have examined whether violent criminality can be associated with mental illness in general or a particular diagnosis within offender populations (McKnight, Mohr, Quinsey, and Erochko, 1966; Nichol, Gunn, Gristwood, Foggitt, and Watson, 1973; Siomopoulos, 1978; Ashford, 1989; Brownstone and Swaminath, 1989; Côté and Hodgins, 1992; Beaudoin, Hodgins, Lavoie, 1993; Coid, Lewis, and Reveley, 1993; Raine, 1993). However, these studies suffer from multiple methodological problems including small or unrepresentative samples, selected  offender groups such as violent inmates or those remanded for a psychiatric assessment, or lack of a comparison population. Consequently, results are inconsistent and any conclusion linking diagnosis to violence within incarcerated populations would go well beyond the scope and quality of the data.

In a large investigation, Toch and Adams (1989) used record linkage technology to study the relationship between mental illness and criminality in New York State (United States). Computer records of 8,379 inmates were matched to New York State Mental Health Services records. Inmates were considered to be suffering from a mental illness if they appeared in the Mental Health files. Of those without a history of mental illness (including substance abuse), 13.8% had a history of recent and remote violence compared to 17% with a history of mental illness or substance abuse. However, 5.8% of those with a combination of psychiatric history and substance abuse committed apparently unmotivated violent acts, compared to only 1.2% of those without a psychiatric history or history of substance abuse. Although the differences reported are actually quite small, the authors concluded that inmates with a history of mental illness or substance abuse were more prone to commit acts of recent violence (occurring within 3 years), and remote violence (occurring after 3 years or more), as well as unmotivated violent acts.

Rice and Harris (1995) studied violent recidivism among matched cohorts of 685 persons who had been referred for a brief forensic psychiatric assessment. Psychopathy, schizophrenia, and alcohol-abuse were the main independent variables of interest. Violent recidivism occurred in 31% of the subjects. Those meeting the criteria for psychopathy (using the 20-item Psychopathy Checklist) were more likely to have an alcohol problem and this combination was related to violent recidivism. Alcohol abuse in isolation was also linked to violent recidivism and persons diagnosed with schizophrenia were less likely to recidivate. Unfortunately, the authors did not control for previous violence or other known risk factors such as age or socio-economic status. At best, therefore, results are only suggestive of a relationship.

Conversely, Valdiserri, Carroll, and Hartl (1986) examined the relationship of psychosis to criminality among persons referred to an on-site mental health clinic in an American prison. Psychotic inmates were four times more likely than non-psychotic inmates to have been charged with a minor offense. There was no difference between the study groups with respect to number of violent offenses. Similarly, Hodgins and Côté (1993) studied the relationship of mental disorder to violent criminality in a representative sample of 461 subjects being held at penitentiaries in Quebec (Canada). A total of 107 individuals were defined as mentally disordered based on the Diagnostic Interview Schedule. These individuals were not found to have a history of more convictions, or more violent  convictions, compared to non-mentally ill offenders.

• Follow-up Studies of Offenders Released into the Community:

The relationship of mental illness to subsequent community adjustment among released offenders has received scrutiny in two large studies (Abram and Teplin, 1990; Feder, 1991; Teplin, Abram, and McClelland, 1994). Neither demonstrates a strong relationship between mental illness and post-release adjustment or recidivism.

Abram and Teplin (1990) were specifically interested in whether persons with dual diagnoses (mental illness and substance abuse) would commit more violent crimes than persons who abused drugs but were not mentally ill. A random sample of 728 released offenders from Cook County Corrections in America were followed for 3 years. Measures of mental illness and substance abuse were collected using the Diagnostic Interview Schedule (DIS) and subsequent arrest data were obtained from the Chicago Police Department, the Federal Bureau of Investigation, and the Illinois Bureau of Investigation. Previous arrests for violent crimes and time at risk (number of days out of jail) were positively associated with subsequent commission of violent crimes. An opiate disorder diminished the probability of a future arrest for a violent crime. However, the authors point out that data were collected prior to the cocaine epidemic in the United States. Mental disorders (schizophrenia, depression, and alcohol disorder) did not predict subsequent arrest for a violent crime after controlling variables such as age or education.

Subsequently, in 1994, Teplin, Abram, and McClelland again studied whether the post-release arrest rates for violent crime for these offenders were related to mental disorder in a six-year follow-up. Those with a severe mental illness, defined as schizophrenia or major affective disorders, had a probability of re-arrest of .43. Those with substance abuse disorders had a probability of .46 of being re-arrested. These differences were not statistically significant and held when prior criminal history and age were statistically controlled. In every diagnostic group, persons with a prior history of violent crime were twice as likely to be re-arrested during the follow-up compared to those with no prior history. Persons with a history of hallucinations or delusions did not have a higher probability of subsequent arrest. Persons with hallucinations and delusions did have a slightly higher number of arrests for violent crimes however this was not statistically significant. This carefully conducted and well-reported study provides compelling evidence against the hypothesis that re-arrest for a violent crime is related to psychiatric diagnosis.

Similar results are reported by Feder (1991) who compared the post-prison adjustment of mentally ill offenders (N=147) to a comparable group of non-mentally ill offenders (N= 400) over an 18-month period. When statistical techniques were used to control for group  differences in criminal history, the only significant factors distinguishing the groups in subsequent arrests were age and prior arrests. Psychiatric status was not significant. Sixty-four percent of mentally ill offenders and 60% of non-mentally ill offenders were re-arrested at least once during the follow-up; 19% of mentally ill and 15% of non-mentally ill for violent crimes. Mentally ill offenders were less likely to receive a sentence involving time and were more likely to be diverted into the mental health system.

A number of smaller or less controlled investigations have also been conducted showing a high prevalence of recidivism (e.g. Guze, Goodwin, and Crane, 1969; Grunberg, Klinger, and Grumet, 1977; Pasewark, Bieber, Bosten, Kiser, and Steadman, 1982; Hodgins and Hébert, 1984; Lindqvist, 1986; Lamb, Weinberger, and Gross, 1988; Menzies and Webster, 1987; McMain, Webster, and Menzies, 1989; Martell and Dietz, 1992), but which cannot be used to support a causal relationship between mental illness and violence.

Summary of Key Findings:

The strongest predictor of violence and criminality has proved to be past history of violence and criminality. This was true for persons with schizophrenia as it was for those with substance abuse disorders.

As yet, there is no consistent evidence to support the hypothesis that mental illness (e.g. schizophrenia or depression) that is uncomplicated by substance abuse is a significant risk factor for violence or criminality, once past history of violence is controlled.

Whether persons with schizophrenia are at risk of violence depends, in part, on the context and the presence of psychotic symptoms. For example, persons with schizophrenia have been found to be at somewhat increased risk of committing violent acts when in the community, especially when they are experiencing psychotic symptoms. Conversely, violent behaviour has been found to be low among hospitalized patients with schizophrenia who are receiving appropriate neuroleptic medication.

The occurrence of violent incidents among hospitalized mentally ill may be increasing. However, a small number of patients, typically those with acute psychotic symptoms or dementia, have usually been found to be responsible for the majority of violent incidents. Most violent incidents leading to hospitalization occur in the home, involve episodes of damage to furniture or minor assaults to relatives.

Formerly hospitalized mental patients may be at high risk of arrest and violence when released into the community, particularly if they have a history of prior arrests or violence or if they experience psychotic symptoms.

Family members (not the general public) are the most likely targets of violence from formerly hospitalized patients in the community.

Substance abuse appears as a significant risk factor for violence and criminality among community, patient, and offender populations. It is unlikely that a member of the public would be at risk of violence from someone with a non-substance abuse disorder.

Studies of police-citizen encounters in both Canada and the United States show that the pattern of criminality of mentally ill and non-mentally ill persons coming into contact with the police is similar; mentally ill are no more likely to be charged with a violent crime compared to non-mentally ill.

The prevalence of substance abuse disorders and mental disorders is high among remanded and provincially incarcerated offenders. Yet, the overall rate of detection of mental illness by correctional staff appears to be quite low. Explanations for the high prevalence of mental illness among incarcerated offenders have included the criminalization of mentally disordered behaviour, the “psychiatrization” of criminal behaviour, and the pathogenic nature of incarcerated settings.

In general, offenders’ post-release adjustment does not appear to be related to major mental illnesses (such as schizophrenia or depression) or substance abuse disorders when prior criminality and age are controlled.

Most generally, individuals who are younger are at higher risk of violence and criminality.

3. Critical Review: Does Mental Illness Cause Violence?

In the previous chapter, the main statistical relationships reported in the literature between mental illness and violence were summarized. However, understanding these is only the first step in critically assessing the question: Does mental illness cause violence? A strict reasoning process which goes beyond demonstrated statistical associations is required to make judgements concerning causal mechanisms. Epidemiology provides such a framework (Lilienfield and Stoley, 1994) that will be applied to assess whether there is sufficient evidence to support the conclusion that mental illness can be said to cause violence.

The starting point for the discussion is the oft-quoted passage from Monahan and Steadman’s now classic literature review published in 1983. Until recently, it has served as the touchstone by which mental health providers and scientists alike have understood the relationship between mental illness and violence.

“The conclusion to which our review is drawn is that the relations between ... crime and mental disorder can be accounted for largely by demographic and historical characteristics that the two groups share. When appropriate statistical controls are applied for factors such as age, gender, race, social class, and previous institutionalization, whatever relations between crime and mental disorder are reported tend to disappear” (cited in  Monahan, 1993, p. 287).

By 1993, Monahan had questioned and indeed reversed this conclusion.

“I now believe that this conclusion is at least premature and may well be wrong for two reasons. First, to control statistically for factors, such as social class and previous institutionalization, that are highly related to mental disorder is problematic. For example, in some cases mental disorder causes people to decline in social class (perhaps because they became psychotic at work) and also to become violent, then to control for low social class is, to some unknown extent, to attenuate the relationship that will be found between mental disorder and violence.... If, in other cases, mental disorder causes people to be repeatedly violent and therefore institutionalized, then to control for previous institutiona- lization also masks, to some unknown degree, the relationship that will be found between mental disorder and violence” (Monahan, 1993, p. 287-288).

Two things are clear from these passages. First, ideas about the relationship between mental illness and violence have changed. Secondly, much of what is found by way of a statistical association between mental disorder and violence will hinge on certain technicalities such as how age, sex, or socio-economic status should be considered in the statistical analysis. The epidemiological framework chosen for this review will clarify these issues as well as highlight the main sources of error in studies of this nature.

Control for Confounding Factors:

Confounding occurs when the effects of two or more factors become mixed in a dataset, making it difficult to see, or actually distorting, the effects of the main study relationship (Last, 1988). The extent to which any variable will be considered to be a confounding factor will depend on the investigator’s understanding of the causal mechanism under investigation. For example, Monahan (1993) postulates a mechanism for the causal action of mental illness on violence that places socio-economic status as one intervening step in the hypothesized causal chain between these variables. In Monahan’s view, persons who become seriously mentally ill drift downward in socio-economic status as their illness increasingly interferes with their ability to work. When socio-economic status is treated as a consequence of mental illness, Monahan is correct in arguing that statistically removing the effects of socio-economic status could seriously distort the results. Any factor that represents a plausible step in the causal chain under study cannot be considered to be extraneous to the analysis and its effects should not be statistically controlled (Rothman, 1986). Unfortunately, the issue is not so easily settled because, in some cases, downward drift may not occur, or may not be the consequence of a mental illness. Thus, the extent to which controlling for socio-economic status would distort  results would depend, in part, on the population studied. In the presence of uncertainty about the causal mechanism, it might be best to assess the relationship between mental illness and violence with and without statistical controls for socio-economic status, in order to compare the differences in the results.

Monahan incorrectly makes the same argument for other factors such as age, or sex. To be considered to be intervening variables, it would have to be argued that age and sex are caused by mental illness. This is clearly not plausible. But, because all of these factors are known to be statistically associated with violence, they could interfere with our ability to draw valid conclusions about the relationship between mental illness and violence, depending upon how they are represented in the study and comparison groups. For example, if the study group of persons with mental illness also contained a disproportionately high number of young males who were prone to violence, a straight comparison across study and control groups would make it appear that there was a statistical association between mental illness and violence. In fact, this apparent association could be explained as a result of the mixing of the effects of age and sex. To assess the true relationship between mental illness and violence, the confounding effects of age and sex would have to be controlled using one of several statistical techniques designed for this purpose. When critically reviewing the literature, then, it is appropriate to consider factors such as age, sex, or past violence as confounding factors that warrant careful control.

Confounding by Definition:

Another highly pertinent issue is that it may be impossible to define violence independent of mental disorder. For a number of psychiatric disorders described in DSM-III-R (and subsequently in DSM-IV) (American Psychiatric Association, 1987, 1994), violent behaviour is a key diagnostic feature. These include antisocial personality disorder, borderline personality disorder, intermittent explosive disorder, and sexual sadism. For a number of other diagnoses, such as schizophrenia, bipolar disorder, and substance abuse, DSM lists violent behaviour as an associated feature, although it is not a symptom. Thus, manifestations of violence may increase the likelihood that these disorders will be diagnosed (Swanson, Holzer, Ganju, and Jono, 1990). In essence, this is ‘confounding by definition’.

Harry (1985) conducted a content analysis of DSM-I, DSM-II, and DSM-III to assess to what degree diagnostic conceptualizations have changed vis-à-vis the relationship between mental illness and violence. The descriptive paragraphs and diagnostic criteria for each disorder were reviewed for words pertaining to violent behaviours. Unfortunately, no distinction was made between words reflecting violence toward others and violence toward the self. Nevertheless, the results are illuminating. In DSM-I, 6 of the 276 possible disorders (2.17%) were ‘violent’. In DSM-II, 9 of the 337 possible disorders were ‘violent’ (2.67%). In DSM-III, this proportion jumped to 162 of 348 or 46.6%! Ninety-one of these (26.15%) included violent words as part of their diagnostic criteria. In DSM-III, the diagnostic groups with the largest number of ‘violent’ disorders were substance use disorders, organic mental disorders, affective disorders (typically suicide and self-harm), and those disorders first manifesting before adulthood.

DSM-I appeared in 1952 and DSM-II appeared in 1968 and was used until approximately 1980, when DSM-III was introduced. A number of authors have remarked on the seeming inexplicable reversal in research findings. Early studies tended not to find a relationship between mental illness and violence but studies conducted during the past 15 years have reversed this trend (Link, Andrews, Cullen, 1992; Teplin, 1985). If we consider that this reversal coincides with the adoption of DSM-III, changing conceptualizations of mental disorder that incorporate notions of violence may be at the root of many current findings.

Possible Confounding due to Psychiatric Medications:

A final issue related to confounding is the effect of psychiatric medications on aggression. In a review of clinical aspects of dangerous behaviour, Menuck (1983) describes a number of iatrogenic or paradoxical drug reactions including:

• Tranquilizer-sedatives (e.g. benzodiazepine and barbiturates) may have a disinhibiting effect on affect and behaviour. Paradoxical drug reactions involving violent behaviour have been reported among incarcerated offenders, psychiatric patients, and control group volunteers receiving these drugs.

• Drugs that are capable of producing hypomania may elicit aggressive behaviour by arousal of the central nervous system. Aggressive behaviour has been reported among persons treated with imipramine and amitriptyline, phenylzine, prednisone, and bromocriptine.
• Neuroleptic drugs sometimes increase aggressivity. This phenomenon has been observed during both low and high dose pharmacotherapy.

Even if a statistical relationship could be demonstrated between mental illness and violence in a number of studies, it would still not be clear to what extent the violence would be due to the mental illness or to the psychopharmacological treatments. Within the context of community care and public perceptions of the mentally ill, however, this may be a subtlety of little practical consequence.

Selecting Subjects to Avoid Bias:

The third issue raised in the earlier passages (Monahan, 1993) that warrants careful thought is how to best deal with prior institutionalizations that may be related to violence.

Epidemiologists recognize this difficulty as a problem in selecting subjects for study and they refer to the resulting distortion that can occur as “selection bias” (Rothman, 1986). In the present context, as Monahan’s example illustrates, selection bias would occur if study subjects represented sub-groups of the mentally ill that were more likely to be violent.

Selection bias is a universal problem for studies using persons who are undergoing treatment for a mental illness, particularly inpatient hospitalization, or those incarcerated for a violent crime. Because both of these groups may be more prone to violence, studies of treated populations could lead to an exaggerated estimate of the effect of mental illness. Neither sub-group is representative of their respective larger populations (i.e., the mentally ill population and the offender populations).

Selection bias is an insurmountable problem for these studies because there is good evidence that:

(a)

Persons with a mental illness who come into contact with health services, particularly hospitals, may be more likely to be violent. For the last two decades, civil committal criteria governing involuntary psychiatric hospitalization have moved away from criteria that were based on a clinical judgement that the individual was in need of treatment toward a standard of dangerousness (Monahan, 1984). In Canada, Alberta was the first to adopt the dangerousness criterion in their Mental Health Act in 1972 (Davis, 1992). Studies that describe an increased incidence of violence among hospitalized psychiatric populations are consistent with this legislative shift toward a dangerousness standard for admission.

(b)

Persons coming into contact with the police because of violent or disturbed behaviour may be more likely to have a mental illness. The more restrictive civil committal criteria are considered to have provided an important impetus for the deinstitutionalization of persons with mental illness from mental hospitals to community care settings. For example, in the United States between 1955 and 1975, the resident population of state mental hospitals declined by more than 365,000 persons (Morrissey and Goldman, 1981). In Canada, between 1961 and 1976, 34,000 patients were discharged from psychiatric facilities with similar trends occurring across Europe (Holley and Arboleda-Flórez, 1988), although perhaps at a more gradual pace (Morrissey and Goldman, 1981).

Based on a recent analysis of mental health legislation in Canada (Arboleda-Flórez and Copithorne, 1994, updates, 1995), it is clear that these laws give police officers considerable discretionary power in their handling of mentally ill persons in the community. All provincial mental health legislation provide the officer with two choices. If these individuals are apparently suffering from  a mental disorder and potentially a danger to themselves or others, the officer may transport them to a psychiatric facility for examination and, if appropriate, treatment. Secondly, the officer may proceed with a charge and an arrest. Psychiatric services may then be sought through the various provisions outlined in the Criminal Code for mentally disordered offenders (see Kunjukrishnan and Bradford, 1985 for a description). Since civil committal criteria have been tightened, some have argued that processing through the criminal justice system has become a more expedient means of removing persons with a mental illness from the community while at the same time gaining entrance to mental health services.

The notion that there is a flow between the mental health and criminal justice systems was first described in 1939 by a British researcher named Penrose. Penrose explained the apparent association between mental illness and crime by documenting an inverse relationship in the size of prison and mental hospital populations across 18 European countries. Where prison populations were extensive, mental hospital populations were small, and vice versa. Basic to Penrose’s theory is the notion that the volume of persons requiring institutional care remains relatively stable and that these individuals are shunted from mental hospital to correctional facility, and back again, as standards and policies change (Holley and Arboleda-Flórez, 1988).

Weller and Weller (1988) have plotted separation data from psychiatric hospitals against admission data from prisons in England between 1950 and 1985. A correlation coefficient of -94 describes a strong inverse relationship consistent with Penrose’s original formulations. Stated another way, knowledge of the psychiatric bed population over this period would have permitted predictions as to the scope of prison populations with only 11.6% of the prison population remaining unaccounted for in the prediction. These authors argue that it is difficult to put forward convincing explanations for such a strong relationship except by postulating that psychiatric hospitals have decanted their patients to prisons. Studies that (a) fail to show differences in violent behaviour of civilly committed psychiatric patients compared to forensic patients (e.g. Beran and Hotz, 1984), (b) show high arrest/conviction rates among persons with mental illness (e.g. Hodgins, 1992; Lindqvist and Allebeck, 1990), and (c) show a high prevalence of mental illness among incarcerated offenders (e.g. Arboleda-Flórez, 1994; Bland, Newman, Dyck, and Orn, 1990; Gingell, 1991) all support the thesis that a sub-population of persons are moving between mental health and criminal justice systems.

The high prevalence of mental illness among incarcerated populations in Canada (e.g. Arboleda-Flórez, 1994; Bland et al., 1990) have been explained in a number of specific ways. Mentally disordered offenders may be arrested at a disproportionately high rate  compared to non-mentally disordered offenders. Persons with mental illness may also be less skilful at crime or more easily caught. Or, once arrested, they may be more likely to plead guilty because of inability to pay, or inability to understand legal representation (Davis, 1992).

Given the wide range of plausible non-etiological explanations for the high prevalence of mental illness among incarcerated populations or the high incidence of violence among psychiatric patients, it is clear that only studies focussing on unselected samples of persons defined as mentally ill or violent can be used to derive etiological inferences. It is unfortunate that recent reviews (e.g. Monahan, 1993; Torrey, 1994) have failed to appreciate the limitations of these bodies of research for drawing etiological inferences.

Gunn (1977, p. 317) has noted:

“....Most discussions on the mentally abnormal offender concentrate on either those who are resident in hospitals or prisons, or on serious offenders, especially those who are violent or sexually deviant. In view of the complexities mentioned above, this selectivity is understandable, but it should always be remembered that it excludes the majority of mentally disordered and the majority of criminals.”

Classification of Mental Illness and Violence
(Information Bias):

Systematic errors in obtaining information that is used to classify subjects on either exposure or outcome factors can result in invalid conclusions (Rothman, 1986). For example, many of the studies examining the relationship between mental illness and violence have relied on institutional records to classify their subjects, such as an admission for a psychiatric illness to classify mental illness or a criminal arrest or conviction for a violent crime to classify violence. Clearly these do not capture all persons who suffer from a mental illness or all violent acts. Estimates of the relationship between mental illness and violence may be inflated or underestimated depending on how subjects are misclassified (Rothman, 1986). To illustrate the problem of underreporting, Dietz (1981) cited a study indicating that in cases of assaultive violence without theft or rape, 62% of attempts and 46% of completed attacks were not reported to police. Lion, Synder, and Merrill (1981) report similar difficulties in psychiatric patient populations.

Gunn (1977) highlights the difficulties associated with relying on secondary data (such as institutional records) for classifying subjects:

“We are all aware that the very existence of mental illness has been challenged and that definitions are extremely difficult to formulate. Yet most of us believe that somewhere in the confusion there is a biological reality of mental disorder, and that this reality is a complex mixture of diverse conditions, some organic, some  functional, some inherited, some learned, and some acquired, some curable, others unremitting. It would be surprising if such a mélange had a clear-cut relationship with any social parameter, specially one which is arbitrarily determined by legislation. Criminal behaviour is simply the breaking of the criminal laws in force at any particular time.”

Too often, official statistics reflect political biases and social trends that may affect these measures and their interpretation. As a result, many investigators have concluded that primary data collected from the general population through the use of self-report measures, rather than official samples, will provide a more accurate picture of the nature and scope of criminal activity and violence (Convit, O’Donnell, and Volavka, 1990).

While population surveys that involve primary data collection provide the best opportunities for overcoming the shortcomings of archival data, they are not entirely without difficulty. Underreporting of violence may be a general problem in self-report measures of violence, particularly if the violence is directed toward children (for which strict legal sanctions exist) or spouses (Swanson et al., 1990). Further, this reporting bias may differ for persons who suffer from mental illness, compared to those who do not. For example, Convit et al. (1990) examined the validity of self-report measures of arrests among psychiatric patients by comparing these to officially reported arrests and found them to be only slightly better than chance alone. Of the 41 patients studied, 66% gave accurate reports, 12% denied having arrests when their record showed arrests, and 22% reported arrests when their official records showed none. While this study was based on an extremely small and selected sample, it does raise the issue of misclassification bias, and highlights the importance of investigators taking steps to minimize this bias in their study designs. It also raises the importance of using appropriate caution to interpret findings, particularly when drawing etiological inferences.

What Comes First? Temporal Ordering of Factors:

In order for mental illness to cause violence, it must precede it. In order to infer causality from empirical evidence, therefore, a clear temporal ordering of events must be established.

In a cohort (i.e. follow-up) study, two or more groups of individuals who differ with respect to the purported causal factor under study (termed “exposure”) are followed through time and compared with respect to their outcomes. An essential element of a cohort study is that all groups are free from the outcome of interest at the outset of the research (Rothman 1986). This makes it possible to establish the temporal ordering of factors with absolute certainty. In the present context, this would require cohorts to be defined on the basis of the presence or absence of mental illness, excluding any individuals who, at the outset, report a past history of violence.

The importance of excluding individuals with a prior history of violence is highlighted by Steadman, Vanderwyst, and Ribner (1978). These authors compared the arrest rates of former mentally ill patients with criminal offenders released in the same jurisdiction in New York State (United States). Discharged mentally ill patients were found to have an overall arrest rate that was substantially higher than the general population. However this masked the fact that these patients differed dramatically with respect to their prior history of arrest. Approximately three-quarters had no previous arrest history and were arrested about as often or less often than the general population. Those with previous arrest rates were arrested more often than the general population. The authors conclude that as deinstitutionalization has changed the composition of state mental hospitals to include a higher proportion of individuals with prior criminal histories, so too have the rates of criminality among former mentally ill patients increased. Epidemiologists refer to this as identifying a cohort that is “at risk” for the outcome. Individuals who, at the outset, have experienced the outcome under study are excluded from study because they are no longer at risk (Rothman, 1986).

In a case-control study, subjects are chosen on the basis of the outcome of interest (in this case violence), then information is collected on the exposure of interest (i.e. previous mental illness). In the present context, cases would be defined on the basis of violence, controls would be defined on the lack of violence. Temporal ordering of factors may be difficult in case-control studies because investigators must rely on participants’ memories to pinpoint the timing of crucial events. Because of the possibility of “recall bias”, epidemiologists require findings from case-control studies to be corroborated by other study designs (ideally cohort studies) prior to drawing etiological inferences.

In a cross-sectional survey, a representative sample of individuals are surveyed and exposure and outcome information are obtained at the same time. Because both exposure and outcome are measured simultaneously, it may not be clear which predated which. For this reason, cross-sectional surveys are typically considered to provide the weakest evidence of causality in epidemiological enquiry (Rothman, 1986).

Epidemiologists adhere to a hierarchy of evidence placing the most credence in statistical associations demonstrated in well-designed and executed cohort studies. Case-control study designs can provide persuasive evidence but are usually not deemed to be sufficiently strong to make a causal judgement. Descriptive cross-sectional studies are used to generate hypotheses for further testing. They are not used to infer causality.

Biological Plausibility:

Finally, the biological plausibility of a hypothesis is an  important epidemiological concern in assessing causality. Biological plausibility refers to whether or not an observed statistical relationship can be interpreted within the context of current biological theories. Biological plausibility is often difficult to assess because the state of the knowledge may be such that biological mechanisms are unknown. Therefore, the absence of a biologically plausible hypothesis does not invalidate a causal judgement. However, the presence of a biologically plausible hypothesis lends certain strength to a causal inference that is supported by strong empirical evidence (Rothman, 1986). Therefore, it is useful to assess whether there are biological mechanisms that have been postulated to link mental illness to violence in a causal framework.

Genetic and inherited diseases, pernicious influences in-utero with a potential effect on the developing brain, perinatal damage to the brain, specific conditions associated with central nervous system pathology, and some personality syndromes as substratum for episodic dyscontrol, have been implicated, both with mental symptomatology and the expression of violence. An association between psychopathy and violence has been proposed, but requires further elaboration.

In 1950, Sandberg discovered a male with an extra Y chromosome (described in Heilbrun and Heilbrun, 1985). This chromosomal abnormality became known as the XYY syndrome. As females have two XX chromosomes, and males have one X and one Y chromosome, it is the Y chromosome that conveys “maleness”. Males with two Y chromosomes, as in the case of Sandberg’s male, were immediately described as “supermales” and endowed with special characteristics such as being extra-tall and extra-aggressive. Soon, reports surfaced from mental and criminal institutions about an abundance of tall men who had committed heinous crimes of violence and who were XYY. Tall men defendants who had committed serious crimes of violence began pleading incompetence on the basis that they had an extra Y chromosome and, therefore, a biological abnormality which caused them to commit a crime. As might be expected, this led to a scientific and legal controversy on the accuracy of the relationship of the XYY syndrome and criminality, specifically, violent crimes. A large community epidemiological study carried out in Denmark settled the controversy. A birth cohort was gathered consisting of 31,436 men. The tallest among them were checked for the extra Y chromosome. Only 12 were found to be XYY, and none of these had ever committed a violent act.

Mednick and Finello (1983), leading exponents on the biology of crime, have noted similarities in findings on the antecedents and correlates of antisocial conduct across nations and continents. Specifically, they call attention to several leads:

1)

the “cultural robustness” of findings such as the unresponsive autonomic nervous system characteristic of delinquents, adult offenders and prison inmates;

2)

cross-national research implicating neuropsychological disturbance and hyperactivity as characteristic of violent offenders; and

3)

slow frequency of electric brain activity that has been used to predict criminal behaviour.

In their own research, Mednick, Gabrielli and Hutchings (1984) compared court convictions of 14,427 adoptees with those of their biological and adoptive parents. They found a statistically significant correlation between the adoptees and their biological parents for convictions of property crimes, but not for violent crime. More significantly, siblings adopted separately into different homes tended to be concordant for convictions, especially if they shared a biological father with a record of criminal behaviour.

The proposal, which appeared over 50 years ago, for a neuroanatomical central nervous system (CNS) mechanism for the expression of emotions and behaviours has led to findings of alterations in CNS serotonin, a neurotransmitter, in association with violent behaviour in animals. These findings have been confirmed by many researchers the world over. The hypothesis that affective disorders in humans are associated with suicidal and violent behaviour has led to numerous replications of experiments reporting an association between low concentrations in the cerebrospinal fluid of 5-hydroxyindoleacetic acid, a metabolite related to serotonin, and impulsive, destructive, and violent behaviour (Brown, Linnoila, 1990; Apter et al., 1990). Equally, researchers and clinicians in many countries have described the beneficial effects of a variety of drugs with CNS activity such as lithium, propranolol, chlorpromazine, clozapine, and other antipsychotics, which are used for the treatment of violent behaviour whether or not associated with mental illness (Greendyke, Schuster, and Wooton, 1984; Craft et al., 1987; Herrera et al., 1988). Paradoxically, some anxiolitics such as the benzodiazepines, have been implicated in triggering violent reactions (Lader and Petursson, 1981).

Despite the XYY fiasco, and the difficulties in conducting this kind of research, some of which are sociopolitical and ethical more than technical ones, a theory and a body of knowledge are solidifying around the hypothesis that some mental conditions, or basic emotional dimensions, are correlated with the expression of violent behaviour. As more and more research findings are pointing towards the presence of brain pathology in major mental conditions such as schizophrenia and affective disorders, a convergence has started to develop, at the biological level, for a similar CNS substratum underlying mental illness and violence.

Unfortunately, the biology of violence has not advanced as rapidly as the biology of mental illness. Thus, it is yet too early to claim that this point has been proven beyond  any controversy. Nevertheless, a link between mental illness and violence remains a biologically plausible hypothesis that warrants future careful study.

Proof or Stereotype?

Does mental illness cause violence or is this perception an unfortunate stereotype?

In discussing the “criminalization” hypothesis, Teplin (1984) has pointed to the desire of some scientists and policy makers to accept hypotheses based largely on intuition and unsystematic observation without subjecting them to adequate empirical testing. She suggests that public policy decisions should be firmly grounded in scientific evidence. In speaking about deinstitutionalization Arboleda-Flórez (1993) also notes that mental health policy decisions have been based on statements of philosophy and social values rather than on solid empirical data and theory.

Much in the way of understanding the relationship between mental illness and violence has been accepted on the basis of intuition and unsystematic observation and, as yet, there remains a lack of adequate empirical testing. Following Monahan’s (1992) judgement, mental illness has become understood as a likely cause of violence and criminality. Recent reviews (Monahan, 1992, Torrey 1994) leave the reader with the impression that an ever progressing science has passed a threshold of evidence that has finally allowed us to conclude that a causal association exists. Tracing the socio-historical roots of the belief that mental illness causes violence from the very origins of Western civilization to present day perceptions (Monahan, 1992) may strengthen our belief in the validity of this conclusion.

However, earlier, more critical reviews (Davis 1991; Teplin, 1983) succeeded in highlighting a number of methodological difficulties that seemed to plague studies in this area. This critical review of the recent literature shows few improvements.

Studies of violence among treated mental patients have demonstrated that these individuals (especially those who abuse substances) may have higher levels of criminality and violent criminality than the general population. Virtually all of these studies have relied on official arrest data to measure criminality to facilitate population comparisons and have assumed that violent crime is an adequate measure of violence. It has been argued that arrests and convictions are even inadequate measures of crime, because seriously disturbed defendants and those with histories of psychiatric hospitalization may be diverted to the mental health system and rehospitalized, rather than arrested. Also, because most crimes do not result in arrests and most arrests do not result in convictions, arrest rates underestimate the total number of arrestable incidents and overestimate the number of guilty verdicts. Studies of police-citizen encounters overcome these problems. It is interesting to note, however, that even these studies (Holley and Arboleda-Flórez, 1988;  Teplin, 1984) have not demonstrated a difference between mentally ill offenders and non-mentally ill offenders with respect to the prevalence of violent offenses.

Studies of mental illness among incarcerated offenders have shown a high prevalence of serious mental illness and substance abuse disorders. These studies have been largely descriptive and have not used comparison groups to assess the extent to which the prevalence of mental illness among incarcerated offenders is higher than could be expected given general population rates. Nonetheless, Canadian prevalence figures of approximately 60% (Arboleda-Flórez, 1994; Bland et al., 1990) leave little doubt that incarcerated offenders are a high risk group. Studies of violence among psychiatric inpatients could be said to have yielded similar findings, despite the difficulties experienced in accurately measuring violence. The logic underlying these investigations is straightforward. If mental illness and violence are causally related, then we might expect to see a high prevalence of mental illness among incarcerated offenders and a high incidence of violence among psychiatric inpatients. While this is true, studies conducted exclusively on institutional populations cannot provide empirical evidence of a causal relationship between mental illness and violence because they have systematically excluded the majority of persons with a mental illness. Because these studies focus on sub-groups of mentally ill that are most likely to exhibit violence, findings from these studies can only be used to disconfirm a causal explanation (i.e. if they revealed lower than expected prevalences).

Link and Stueve (1995) argue that the consistency of findings across the various populations studied, despite their specific limitations, must be considered as evidence of causality. Methodological weaknesses in one area cancel the methodological weaknesses in another. This perspective overlooks the importance of selection bias as one explanation for the consistency of results reported. Only studies that examine the relationship of mental illness and violence in unselected and representative samples of mentally ill can address the issue of causality. To date, only two studies (supporting three analyses) have examined the relationship between mental illness and violence in unselected samples of adults living in the general population, one in Canada (Bland and Orn, 1986) and one in the United States (Swanson, 1993; Swanson et al., 1990). Both studies used a structured diagnostic interview schedule (DIS) to survey representative samples of the population to arrive at DSM-III diagnoses. Both studies represent the “state-of-the-art” with respect to current psychiatric epidemiological methods. Because both studies have overcome the problem of selection bias by focussing on non-institutionalized samples, results are potentially useful in drawing epidemiologic inferences of causality.

Both studies report a statistical relationship between mental disorder and violence, particularly among persons  with substance abuse disorders. However, what is not clear from these findings is the extent to which this statistical relationship could be explained by definitional confounding (described earlier) where almost half of DSM-III diagnoses, particularly substance abuse disorders, could be defined in part on the basis of violent behaviours. To compound this problem, both studies abstracted diagnostic items from the DIS interview that referred to violent behaviours and used these as the basis of their measure of violence. The DIS items referring to violent behaviour used by Swanson and colleagues (1990) were taken from the diagnostic sections for antisocial personality disorder and alcohol abuse and dependence. Thus, it is not surprising that a significant statistical relationship was reported in this study between substance abuse disorders (single or comorbid) and violence. Using a similar procedure, Bland and Orn (1986), restricted their analysis to three diagnostic categories, antisocial personality disorder, substance abuse disorders, and major depression.

In addition, the cross-sectional designs of the studies make it difficult to establish the temporal ordering of the factors with any degree of certainty. The American study (Swanson, 1993) employed a one-year period prevalence measure of both mental illness and violence such that individuals meeting the criteria for either of these during the year prior to the survey would have been counted positively. Thus, violence could have predated the mental illness or vice versa. The Edmonton study (Bland and Orn, 1986) used a lifetime prevalence measure such that individuals meeting the diagnostic criteria at any point in their lives would be considered to be positive for the study factor. Again, it is not clear whether the mental illness predated the violence.

The American study was designed to provide longitudinal data. Participants were re-contacted and re-interviewed in a second wave one year following the first interview. Longitudinal studies of rare events such as violence require very large sample sizes. However, this study overcame this problem by combining representative samples from five cities to provide a total sample size of over 20,000. This is sufficiently large to provide follow-up information on new cases of mental illness with no prior history of violence. If the issue of definitional confounding could be overcome and independent measures of mental illness and violence achieved, this study could provide information that could be used to explore an etiological relationship between mental illness and violence.

Finally, a word on the generalizability of findings from the United States, where much of the research has been done, to Canadian populations. Both Borzecki and Wormith (1985) and Davis (1992) address this issue. The trend toward deinstitutionalization in Canada was as marked as in the United States with massive reductions in the census of hospital populations occurring in both countries. Restrictive admission policies in both countries, based on a standard of dangerousness, ensure that competent patients who are not dangerous to themselves or to others can refuse hospitalization. A major difference between the countries occurs in the access of persons with a mental illness to appropriate community treatment resources. Universal access to medical care coupled with greater spending on community mental health programs in Canada suggests that there may be less pressure to use criminal justice alternatives for mentally disordered persons living in the community (Borzecki and Wormith, 1985). Nevertheless, the high prevalence of mental illness noted in incarcerated populations in Canada (Arboleda-Flórez, 1994; Bland et al., 1990) and the consistency of findings regarding police-citizen contacts across Canadian (Arboleda-Flórez and Holley, 1988) and American studies (Teplin, 1985) suggests that similar selection pressures are operating in both countries.

Conclusions:

In light of the foregoing annotated review and discussion, it is possible to identify that which we are relatively confident of, and that about which we remain uncertain.

Given the methodological problems that have plagued this field, a causal inference that mental illness causes violence cannot yet be made for the following reasons:

a)

Studies examining the relationship between mental illness and violence have been largely restricted to selected offender or patient populations. Because of their selected nature, these studies are not sufficient to draw etiological inferences about the role of mental illness in causing violence in general. They only provide evidence of an association among selected sub-groups of persons who come into contact with services because they are more likely to be violent in the first place.

b)

General population studies that have overcome this selection bias have shown a statistical association between some mental illnesses and violence. However, these studies have been cross-sectional in nature so have been unable to establish the temporal ordering of study factors. Therefore, at best, they could provide only weak evidence to support an etiological inference. In addition, however, it is possible that the statistical associations noted are an artifact of the manner in which mental illness and violence were defined. These studies have failed to derive measures of mental illness that are independent of violence. Given this problem, findings from these studies cannot be used to form the basis of an etiological argument.

Without further well-controlled epidemiological investigations, there is insufficient evidence to infer an etiological relationship between mental illness and violence.

Based on the foregoing review, however, we can be relatively  confident that:

a)

the prevalence of mental illness (particularly substance abuse disorders) among incarcerated populations is high, reflecting a population that is in particularly great need of services;

b)

former mental patients may be at high risk of arrest and violence when released into the community, particularly if they have a history of prior arrests or violence or if they experience psychotic symptoms;

c)

family members (not the general public) are the most likely targets of violence from former mentally ill patients in the community; and

d)

hospitalized mental patients are at high risk of committing violence, particularly if they have a history of prior violence or if they experience psychotic symptoms.

Potential Directions for Future Research:

• Further research using selected samples of patients or incarcerated offenders is unlikely to further our knowledge on this issue. Future research will have to proceed with attention to a number of critical design issues including the:

a)

development of independent measures of mental illness and violence that can be used within the context of primary data collection efforts to avoid confounding by definition;

b)

measurement of the relationship between mental illness and violence in large and unselected populations, with appropriate exclusions or controls for persons with a prior history of violence; and

c)

clear temporal ordering of factors such that it is unequivocal that mental illness predates any expression of violence.

• The paucity of published literature incorporating the perspective of those who have a mental illness should also be addressed. The views and experiences of consumers and their family members would contribute further to the examination of violence as it is experienced by these individuals in community and hospital settings, and among peers. This is an area where future work is needed.
• While not the subject of the current review, the research reviewed in this study raises questions in regard to the extent to which the following issues are being addressed:
• Appropriate identification of mental illness and substance abuse problems among incarcerated offenders in correctional settings.
• Management of disturbed behaviour by the mentally ill that is often directed towards family members. Such approaches are being used in hospital settings.
• Appropriate access to community resources for former mental patients in the community.
• Appropriateness of treatment for the mentally ill in correctional and community settings.

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Appendix A:
Annotated Bibliography

Introduction:

The following bibliography contains annotations to key quantitative and qualitative articles bearing on the central study questions relating to mental illness and violence. For ease of reading, articles have been grouped according to major topic headings. Topic areas have been grouped so as to reflect the various lines of inquiry and evidence that have accumulated in this area. The areas are:

• Community Studies
• Studies of Psychiatric Patients
• Studies of Incarcerated offenders
• Other Empirical Studies of Interest
• Review Articles and Key Position Papers.

Within each group, the annotations are presented alphabetically by author and title. A brief glossary of key technical terms is contained in Appendix B for reference.

To assist the non-scientific reader in drawing pertinent comparisons across articles, all empirical studies have been critically reviewed and summarized according to a standardized abstract structure: (a) purpose and objective; (b) research design; (c) study setting; (d) study subjects; (e) measures used; (f) main findings; (g) conclusions; (h) methodological critique; and (i) causality. A comment section is also included in the “Other Empirical Studies of Interest” category. In the “Review Articles and Key Position Papers” category, key points relevant to the critical review are highlighted, and, where appropriate, commentary is provided.

Causality:

The term ‘causality’ refers to whether or not the study could be used to arrive at a causal determination regarding the relationship between mental illness and violence. Causality was judged strictly according to epidemiological criteria. At the outset, it is important to point out that no study provided strong evidence in support of a causal relationship between mental illness and violence.

Community Studies: Empirical Studies Based on General Population Samples:

Barring other methodological problems, empirical studies based on representative samples of the general population are generally preferred for drawing causal inferences because they avoid “selection bias” (Rothman, 1986). Selection bias is a systematic error that creeps into studies when subjects are chosen from treated or institutional populations that are known to be at higher risk of violence. When rates of violence in selected groups are compared to general population, the selected populations will often appear to have higher rates of violence. This is usually attributable to the fact that they were more violence-prone to begin with, not because mental illness causes violence. Because they are time-consuming and complex, population-based studies are generally few in any area of inquiry. They are also costly because large samples are required to obtain large numbers of persons with mental illness and violence to support statistical analysis.

Studies of police-citizen encounters have been included in this section to acknowledge the pivotal role of police decision-making in determining what will happen to those persons with a mental illness who, while living in the community, may engage in disordered or violent behaviour. They may either be processed through the criminal justice system, or they may be taken to a psychiatric facility for assessment and treatment. Given police discretionary power, persons who are thought to be mentally ill and who are violent may be arrested more often than non-mentally ill offenders. This could account for statistical relationships between violent criminality and mental illness in incarcerated populations. The possibility of shifting mentally ill offenders into the criminal justice system has been referred to as the “criminalization of the mentally ill”. This poses serious selection problems for studies that (a) use arrest or conviction for a violent offense as a measure of violence, or (b) select subjects for study from arrested or incarcerated populations.

Arboleda-Flórez, J. and Holley, H.L. (1988) Criminalization of the mentally ill: Part II. Initial detention. Canadian Journal of Psychiatry, 33, 87-95.

See also: Holley, H.L. and Arboleda-Flórez, J. (1988). Criminalization of the mentally ill: Part I. Police perceptions. Canadian Journal of Psychiatry, 33, 81-86.

Purpose and Objective: Compare police-identified ‘mentally ill’ with police-identified ‘normals’ on the basis of sociodemographic, legal, clinical, and outcome variables. The authors set out to test the hypothesis that the groups would differ in terms of important socio-clinical characteristics.

Research Design: Prospective longitudinal study.

Setting: Calgary, Alberta, Canada.

Study Subjects: Study subjects were 350 persons who came into contact with the police during the latter two weeks of October, 1984.

Measures: Police were asked to rate subjects’ observable behaviour on a continuum from normal (score of 0) to severely abnormal (1-7). Then police were asked to attribute what they believed the cause of this behaviour to be, alcohol, drugs, mental illness or other, and to indicate whether they believed a psychiatric examination was warranted. Arrest information was provided by the police reports.

Main Findings: A total of 89 individuals were identified by police as acting abnormally during the arrest; 261 were considered to be acting normally, given the situation. Police-identified mentally ill did not record a greater number of crimes against persons, property, or miscellaneous charges compared to police-identified normals. Police-identified mentally ill recorded fewer victimless crimes and slightly more motor traffic violations.  Police-identified mentally ill were slightly more likely to be recommended by police for detention compared to normals but the difference was not large. They were no more likely to be detained compared to normals.

Conclusions: Because any differences noted between the study groups were small, the authors accepted the conclusion that the groups did not differ in important social, clinical, or legal respects.

Methodological Critique: It is not clear to what extent misclassification of mentally disordered offenders by police could account for the lack of differences noted across the groups. Also, because this study focussed on individuals who came into contact with the police, findings cannot be used to draw etiological inferences concerning causal relationships between mental illness and violence. It is interesting to note, however, that despite a different methodology, these findings are consistent with those reported by Teplin (1985) in her study of police-citizen contacts.

Causality: A causal inference cannot be made on the basis of these findings.

Bland, R. and Orn, H. (1986). Family violence and Psychiatric disorder. Canadian Journal of Psychiatry, 31, 129-137.

Purpose and Objective: To study the relationship between family violence and psychiatric disorder in the general population.

Research Design: Cross-sectional survey.

Setting: Edmonton, Alberta, Canada.

Study Subjects: A representative sample of 1200 residents living in the community.

Measures: Psychiatric disorder was measured using the Diagnostic Interview Schedule (DIS), a structured questionnaire for lay-interviewers that is computer-coded to generate DSM-III/R diagnostic categories. Lifetime prevalence of three diagnoses were examined (1) antisocial personality disorder, (2) major depression, and (3) alcohol abuse/ dependence. Any individual meeting the symptoms for these disorders at any time in their lives would be recorded as positive for mental disorder. Measures of family violence were derived from DIS items covering the subject’s relationship with a spouse or partner, violence or neglect towards children, and violence outside of the family. This questionnaire focused on physical abuse (rather than emotional or psychological abuse) measured by questions about behaviours such as hitting or throwing. Questions were worded to reflect lifetime prevalence of these behaviours.

Main Findings: Nearly 55% of those with a diagnosis were involved in violent behaviour compared to 15.5% of those with no diagnosis. Persons with one or more of the three diagnoses studied were 6.5 times more likely to be involved in violence than those without a disorder. The risk of violence was greatly elevated among those diagnosed with a comorbid alcohol abuse disorder. For example, where alcohol was combined with antisocial personality and/or  depression, 80-93% were involved in violence.

Conclusions: The authors do not propose a simple cause and effect explanation for their findings. Rather, they suggest that their findings should alert clinicians that, when seeing persons with psychiatric disorders, family violence may be a possibility. This particularly applies to those patients with comorbid alcoholism.

Methodological Critique: As the authors point out, findings from this study cannot be used to infer a causal relationship between mental disorder and violence. Because the study used cross-sectional data and lifetime prevalence figures for both mental disorder and family violence, no assumptions can be made about the temporal ordering of these factors. Therefore, the violence may actually have preceded the mental illness. Further, DSM-III diagnoses of antisocial personality disorder and alcoholism are two of the disorders that are most likely to be defined in terms of violent behaviours. Therefore, any observed association between these and violence is likely to be a result of the way in which the disorders have been defined.

Causality: A causal inference cannot be made on the basis of these findings.

Bonovitz, J.C. and Bonovitz, J.S. (1981). Diversion of the mentally ill into the criminal justice system: The police intervention perspective. American Journal of Psychiatry, 138(7), 973-976.

Purpose and Objective: This study is an evaluation of the effects of the Pennsylvania Mental Health Procedures Act passed in 1976. The authors hypothesized that the police would be asked to handle more incidents involving mentally ill individuals after the passage of the Act and that officers would use the Criminal Code to expedite the removal of these individuals from the community.

Research Design: Although the authors do not name their design, the data collection procedures are consistent with a historical cohort study.

Setting: A suburban police department serving a population of 100,000 in Upper Darby Township, Pennsylvania, USA.

Study Subjects: The authors studied an undisclosed number of police incidents involving mentally ill individuals.

Measures: Archival data from 1975-1979 from the police files were used to identify reports in which subjects were clearly identified as “mentally disturbed”. During a six-month period in 1979, 248 incidents were studied in more detail as to their outcome.

Main Findings: Mental illness-related incidents increased 227.6% from 1975 to 1979 whereas non-mental illness-related incidents decreased 9% during this time (excluding felonies which rose to 5.6%). There was an 82% increase in the number of disorderly conduct offenses during this time period, in part because of a change in the  way these were classified. Considering the 248 incidents that occurred during six months in 1979, police officers made 13 arrests.

Conclusions: The authors did not comment on the increased number of police-mentally disordered incidents during the time period but did note that their data did not support the hypothesis that noncommittable mentally ill were being arrested and jailed as an expedient means of removing them from the community.

Methodological Critique: This study is short on methodological detail, for example the total number of incidents studied. Nevertheless, it does provide evidence to indicate that mentally disordered offenders have increasingly come into contact with the police for socially disruptive behaviours and that police discretion plays an important role in their disposition. The police in this community had taken specialized training to recognize signs of mental health problems, and to improve their techniques for resolving such incidents. Perhaps, as a result, they firmly believed that these individuals should not be arrested or held responsible for minor criminal offenses. These findings have important implications for studies focussing on incarcerated offenders because they clearly demonstrate the importance of police decision-making and highlight the selected nature of incarcerated samples.

Causality: A causal inference cannot be made on the basis of these findings.

Hodgins, S. (1992). Mental disorder, intellectual deficiency, and crime: Evidence from a birth cohort. Archives of General Psychiatry, 49, 476-483.

Purpose and Objective: To examine the relationship between mental disorder and crime and the relationship between intellectual deficiency and crime.

Research Design: The author describes the research design as a longitudinal prospective study of a birth cohort to age 30 years. However, data were collected from central registry files in 1983. Therefore, this study could more properly be described as a historical cohort study design.

Setting: Stockholm, Sweden.

Study Subjects: Study subjects were identified from among the 15,117 persons born in Stockholm in 1953 and still residing there in 1963.

Measures: Mentally ill were defined as those having had a psychiatric admission (N=603). Intellectually handicapped subjects (N=192) were defined as those who were placed in special high school classes but never admitted to a psychiatric ward. The comparison group consisted of all those who had never been admitted to a psychiatric ward or to an institution or class for the intellectually handicapped. Crime was measured by criminal conviction data obtained from a central registry. Violent crimes included all offenses involving the use or threat of physical violence (e.g. assault, rape, robbery, unlawful threat, and molestation).

Main Findings: Compared to their “normal” controls, men with major disorders were 4.16 (95% CI, 2.23 to 7.78) times more likely, and women were 27.45 (95% CI, 9.80 to 76.88) times more likely to have been convicted of a violent offense. Note that the wider confidence intervals for women reflects their smaller sample size.

Conclusions: The author considered that the result of this study supported the view that aggressivity is associated with mental illness.

Methodological Critique: Findings are biased in favour of a relationship between mental illness and violence because they were based on a subgroup of the mentally ill (those admitted to a psychiatric facility) who are known to be more likely to be dangerous. As such, these findings cannot be used to draw etiological inferences concerning the general relationship between mental illness and violence. Also, while the study design would have allowed for temporal ordering of events, it is not clear whether criminality occurred subsequent to the mental illness in every case. The author does comment that the criminality of subjects who eventually developed major mental disorders often appeared in early adolescence, well before the mental disorder was diagnosed. This statement indicates that study factors have not been temporally ordered.

In a Letter to the Editor, Weiler [1994, Archives of General Psychiatry, 51, 71] points out that 43% of women and 40% of the men with major mental disorders also had a substance abuse diagnosis. Because those with substance abuse problems were 20 (men) and 32 (women) times more likely to be convicted, the tendency to commit crime may be a function of substance abuse and not major mental illness. If the substance abusers were removed from this group, it would be plausible to expect that the rate of crime would be lower among those with major mental illness.

Causality: A causal inference cannot be made on the basis of these findings.

Monahan, J., Caldeira, C. and Friedlander, H.D. (1979). Police and the mentally ill: A comparison of committed and arrested persons. International Journal of Law and Psychiatry, 2, 509-518.

Purpose and Objective: To provide information describing how police use their discretionary power vis-à-vis persons with a mental illness.

Research Design: Although not specified by the authors, the data collection procedures used are consistent with a cross-sectional survey.

Setting: Orange County, California, USA.

Study Subjects: The study subjects were 100 police officers from various cities. The authors do not describe how the officers were selected, but make reference to a random sample in their conclusions. As no sampling strategy is described, it is unclear whether results can be considered to be representative of all police officers or  whether they simply reflect the beliefs of the 100 that were studied.

Half of the officers were interviewed subsequent to their having petitioned a person for involuntary civil committal and half were interviewed after having booked a person for arrest on a criminal charge. It is not clear whether the latter group consisted of specific experiences with mentally ill offenders booked on a criminal charge.

Measures: The officers reported their perceptions of the 100 persons they arrested or committed with respect to severity of mental illness, dangerousness, and grave disability.

Main Findings: Committed persons were more likely to be perceived as mentally ill compared to those arrested. In addition, police perceived committed persons to be slightly more likely to be violent toward others, 5 times more likely to be gravely disabled, and 20 times more likely to be harmful to themselves. In 30% of the arrests, the police could have petitioned for civil committal. They did not because they did not believe the degree of mental illness, grave disability, or violence was sufficient to sustain a committal. Similarly, in 30% of the committals, police could have proceeded with an arrest. Police chose to commit because they believed that the individuals lacked criminal intent or that they would benefit from treatment.

Conclusions: The authors believe that their study has produced little evidence to support the hypothesis that seriously mentally ill persons are criminalized or that serious law breakers are being psychiatricized.

Methodological Critique: As the authors did not have an independent measure of mental illness against which to judge the validity of police perceptions of mental illness, their conclusion that mentally ill persons are not criminalized or criminals are not psychiatricized goes beyond the scope of their data. The main point of interest for the present review is that detention in mental hospitals or jails is the final outcome of a series of decisions made by various authorities. Therefore, samples of mental patients or criminals are not representative of all individuals and may be selected into these institutions based on the gatekeeper perceptions of the severity of mental illness or propensity toward violence.

Causality: A causal inference cannot be made on the basis of these findings.

Swanson, J.W. (1993). Alcohol abuse, mental disorder, and violent behavior: An epidemiologic inquiry. Alcohol, Health & Research World, 17(2), 123-132.

Purpose and Objective: The aim of this study is to test five hypotheses that have been postulated concerning the relationship between mental illness, alcohol abuse, and violence:

1.

The alcohol abuse hypothesis postulates that  the relationship between mental disorder and violence can be largely explained by the association between alcohol abuse and violence.

2.

The sociodemographic hypothesis postulates that the relationship between mental illness/alcohol abuse and violence is a result of the common socio-demographic correlates in these groups, particularly gender, age, and socio-economic status.

3.

The comorbidity hypothesis suggests that the combination of alcohol abuse and mental disorder results in a substantially greater risk of violence than does either condition alone and occurs more often in men of lower socio-economic status.

4.

The institutional selection hypothesis postulates that the apparent relationship between mental illness and violence can largely be explained by a bias in the populations studied. Most studies focus on persons who have been involuntarily treated or incarcerated which are more likely to be violent.

5.

The psychopathology hypothesis suggests that the increased rates of violence observed among institutionally defined populations is a result of the greater psychiatric and alcohol abuse symptomatology of those individuals most likely to be found in these settings.

Research Design: Cross-sectional survey.

Setting: Data reflect two of the Epidemiologic Catchment Area (ECA) sites in the United States, Durham and Los Angeles.

Study Subjects: A representative sample survey of 7,053 adults.

Measures: As in previous ECA studies, psychiatric disorder was measured using the Diagnostic Interview Schedule (DIS), a structured questionnaire for lay-interviewers that is computer-coded to generate DSM-III/R diagnostic categories. A one-year period prevalence of psychiatric disorder was used such that a person was counted as a case if they met the DSM-III criteria for a given disorder during the 12 months preceding the interview. Four items from the DIS were also used to define violence: (1) using a weapon in a fight since age 18, (2) having been in more than one fight in which blows were swapped since age 18, (3) ever hitting or spanking a child hard enough to injure, and (4) persons who were married or had lived with someone as if married were asked if they had ever hit or thrown things at their wife or partner. For the first four questions, respondents were asked when was the last time they did any of these things. Based on these answers, a four-item violence index was developed reflecting violent behaviour toward others during the one-year period prior to the interview. A respondent was counted as “violent” if one or more of the items was answered positively.

Main Findings: A total of 193 individuals were identified as violent using the measures described above. Five statistical models were tested—one relating to each of the study hypotheses. Results failed to support the alcohol abuse hypothesis or the socio-demographic hypothesis. Modest support was found for the remaining three hypotheses.

Conclusions: Major mental illnesses that were uncomplicated with alcohol abuse were associated with an increased risk of violence. Persons with comorbid mental and substance abuse disorders were at even greater risk of violence. The apparent increase in violence among younger, lower socio-economic males was found to be largely due to the increased prevalence of alcohol abuse and comorbidity in this group. A history of arrest and psychiatric hospitalization was also found to be associated with an increased probability that a person would be violent.

Methodological Critique: The hypotheses tested in this study are clearly conceptualized and described. The cross-sectional nature of this study precludes us from identifying the temporal ordering of study factors and, therefore, from drawing clear causal inferences from the findings. However, results are interesting and suggestive, particularly given the controversy in the literature regarding the role of alcohol abuse as a causal factor in violence among persons with a mental illness, and the uncertainty about how to deal with socio-economic status. The authors attempted to control for the fact that the questions used to identify violence were among those used to diagnose some mental illnesses by excluding those from the analysis. What remains unclear is the extent to which current diagnostic practices, in general, reinforce the relationship between mental illness and violence through the DSM nosology.

Causality: Although well-executed and analyzed, this study does not provide sufficient evidence to draw a causal inference.

Swanson, J.W., Holzer, C.E., Ganju, V.K. and Jono, R.T. (1990). Violence and psychiatric disorder in the community: Evidence from the Epidemiologic Catchment Area Surveys. Hospital and Community Psychiatry, 41(7), 761-770.

Purpose and Objective: To examine the relationship between violence and psychiatric disorder among adults living in the community.

Research Design: Cross-sectional survey.

Setting: The Epidemiological Catchment Areas in the United States (New Haven, Baltimore, St. Louis, Raleigh-Durham, and Los Angeles).

Study Subjects: Representative sample surveys of the adult household resident population were surveyed in 1980 and 1983 with 3,000-5,000 residents per site. Data for this analysis were pooled from the Baltimore,  Raleigh-Durham, and Los Angeles samples for a sample size of 10,059. Data were weighted based on respondents’ probabilities of selection.

Measures: Psychiatric disorder was measured using the Diagnostic Interview Schedule (DIS), a structured questionnaire for lay-interviewers that is computer-coded to generate DSM-III/R diagnostic categories. A one-year period prevalence of psychiatric disorder was used such that a person was counted as a case if s/he met the DSM-III criteria for a given disorder during the 12 months preceding the interview. Five items from the DIS were also used to define violence: (1) hitting or throwing things at a spouse or partner; (2) spanking or hitting a child hard enough to cause bruises; (3) fist fighting since age 18 with someone other than spouse; (4) using a weapon (e.g. stick, knife, or gun) since age 18; and (5) getting into physical fights while drinking. Individuals were counted as positive for violence if they had responded positively to one or more items and said that the behaviour had occurred within the year prior to the interview. A measure of socio-economic status (based on occupation, educational level, and household income) was also used.

Main Findings: Individuals in the community meeting the criteria for a DIS/DSM-III psychiatric disorder were more likely to engage in violent and assaultive behaviour compared to those that did not meet the criteria for a DIS/DSM-III disorder. For example, more than half of the 368 individuals reporting violent behaviour in the preceding year met the criteria for a psychiatric disorder compared to 19.6% of non-violent offenders. The highest percentages of violence were reported among substance abusers (19.2% to 34.7% depending on the category). With the exception of phobias which showed a prevalence of violence of 5.0%, all other diagnostic categories (e.g., schizophrenic disorders, depressive disorders, and anxiety disorders) showed prevalences ranging from 10.7% to 12.7%. With one exception, each separate disorder category studied (without regard for multiple diagnoses) was associated with a higher risk. Persons with non-comorbid anxiety disorder had the same rate of violence as those with no disorder. Those with affective disorder were at only slightly increased risk. Those with schizophrenia were at somewhat elevated risk but not as great as public perceptions would suggest. Conversely, those with substance abuse disorders were at greatly elevated risk and also appeared to commit more severe acts of violence with greater frequency.

The percentage of respondents reporting violent behaviour increased from 2.1% among those with no diagnosis, to 6.8% among those with 1 diagnosis, 17.5% for 2 diagnoses, and 22.4% for 3 or more diagnoses.

Conclusions: Individuals in the community with psychiatric disorders are more likely to engage in assaultive behaviour than those who are not mentally ill. Alcohol and drug abuse and the presence of more than one diagnosis increase the risk of violence substantially.  Public fear of persons with schizophrenia living in the community is largely unwarranted, though not totally groundless. Findings indicate that persons are at much greater risk of being assaulted by a person with a substance abuse disorder than by someone suffering from a major mental illness such as schizophrenia.

Methodological Critique: While this study represents state-of-the-art psychiatric epidemiology, it can be used only to suggest a statistical association between mental illness and violence. Because data were drawn from a cross-sectional survey, the temporal ordering of factors could not be established. Both mental disorder and violence were measured during the same one-year period. Therefore, findings cannot be used to infer causality. Second, as the authors point out, the measures of violence were less than ideal because they reflected DIS questions that were used, in part, to arrive at a diagnoses of mental disorder. Thus, some level of association would be expected by definition.

Causality: A causal inference cannot be made on the basis of these findings.

Teplin, L.A. (1985). The criminality of the mentally ill: A dangerous misconception. American Journal of Psychiatry, 142(5), 593-599.

Purpose and Objective: To assess the relative criminality of mentally disordered persons by focussing on the initial point in the criminal justice system to avoid biases associated with police discretionary powers of arrest.

Research Design: Unspecified by author. Subjects were observed within the context of the police encounter, then arrest data were collected. This is consistent with a short-term follow-up design.

Setting: Large metropolitan city in the United States (population over one million persons).

Study Subjects: Police officers (N=283) were randomly selected and observed, first hand, in their day-to-day interactions with the public. Observations were conducted during all hours of the day, on all days. Evenings and weekends were oversampled. Data were collected in two precincts reflecting a wide range of socio-economic profiles.

Measures: It was not feasible for researchers to conduct full-scale structured diagnostic assessments within the context of police-citizen encounters. Therefore, a symptom checklist that listed characteristics of severe mental disorder (confusion or disorientation, withdrawal or unresponsiveness, paranoia, inappropriate or bizarre speech and/or behaviour, self-destructive behaviours) was used to measure mental illness. Subjects were defined as suffering from a mental disorder if they possessed at least one of these traits and received a global rating of severe mental disorder by the fieldworker. Results from this checklist were validated against findings from 61 randomly selected jail detainees who underwent the Diagnostic Interview Schedule with 93.4% agreement on the definition of severe mental disorder. Criminality was measured by arrest. Crimes were divided into violent personal crimes, interpersonal conflicts, major property crime, minor property crime, public health, safety or decency offenses, and public order offenses.

Main Findings: Police encounters with severely mentally disordered persons occurred infrequently (4% of 2,122 persons). Mentally disordered were more likely to be subjects of concern or objects of assistance and only slightly more likely than non-mentally disordered to be considered suspects. For those who were suspects, type of crime was not related to the presence or absence of mental disorder. The mentally ill did not commit serious crimes at a rate disproportionate to their numbers.

Conclusions: The pattern of crime among mentally disordered suspects is substantially similar to non-mentally disordered suspects.

Methodological Critique: The major strength of this study is that a representative sample of all detected violations (i.e. contacts) were examined regardless of police officer’s dispositions. This permitted researchers to control any potential bias arrest rates resulting from police officer’s propensity to arrest mentally ill more frequently than non-mentally ill, once initial contact had been made. A second strength of this study is the reliance on observational data, rather than archival or secondary data to measure mental illness and arrest. Finally, because a symptom checklist was used, researchers have succeeded in deriving a definition of mental illness that is largely independent of criminality and have avoided the ‘confounding by definition’ that has predominated studies using DSM-III/R criteria. In short, this study provides compelling evidence to support the conclusion that there are no important differences between mentally disordered and non-mentally disordered persons who contact the police with respect to the type of crimes they have been alleged to have perpetrated.

Causality: A causal inference cannot be made on the basis of these findings.

Studies of Psychiatric Patients

The following section includes studies of the relationship between mental illness and violence among psychiatric patients. Given that all of the study samples consist of persons who have come into contact with hospital services, the validity of the research findings in this area are threatened by selection bias. Because of this, it is never clear whether associations noted in hospitalized samples actually reflect associations that exist in the population at large. In addition, many of these studies lack a comparison group, making it impossible to assess whether rates of violence are higher or lower than would be expected. Because of the selected samples, research in this area cannot be used to substantiate the proposition that the mentally ill are more violent than the non-mentally ill.

Asnis, G.M., Kaplan, M.L., van Praag, H.M. and Sanderson, W.C. (1994). Homicidal behaviours among psychiatric outpatients. Hospital and Community Psychiatry, 45(2), 127-132.

Purpose and Objective: The aim of this study was to further qualify the assessment of violent behaviour by focusing on behaviours that the patient specifically identifies as homicidal, including homicidal ideation, plans, and attempts. The second goal was to determine those characteristics which differentiate patients with past homicidal behaviours from patients who show no homicidal tendencies.

Research Design: Although the authors did not specify, the data collection procedure is consistent with a descriptive survey.

Setting: A nonprofit hospital in Bronx, New York.

Study Subjects: The subjects for this study were 517 patients who requested treatment at the outpatient psychiatry department. There were 204 (40%) males and 313 (60%) females ranging in age from 13-87 years.

Measures: Self-rating forms were used including: (1) the Harkavy-Asnis Suicide Survey demographic form; (2) the Homicidal Behaviours Survey and; (3) the revised Symptom Checklist 90. Each patient also underwent a semi-structured interview that included a psychiatric history and mental status evaluation. These were conducted by a psychologist or psychiatrist. Patients received a DSM-III-R diagnosis.

Main Findings: A total of 114 (22%) reported past homicidal ideation, and 41 of those subjects (8% of the total sample) reported that their homicidal thoughts persisted for at least seven days. Forty subjects (8%) reported having a homicidal plan. Twenty-two subjects (4%) reported a past homicide attempt. No significant differences were found in diagnosis for those with a past homicide attempt compared to those without homicide tendencies. In addition, the homicide attempt group reported significantly more suicidal ideation and attempts compared to the homicidal ideation group. There was an 8% difference between males and females regarding homicidal ideation and attempts (males 27%, females 18%).

Conclusions: The authors concluded that the rate of homicide attempts in the current study is considerably lower than the 10% rate of physically assaultive acts reported by other researchers. Given the observed relationship between current and past homicidal behaviours, the authors advocated including a careful assessment of past history of violent behaviours as part of the routine psychiatric evaluation. The authors recognized that the inherent limitations of self-report instruments and the retrospective nature of the study limited the findings. They do not suggest that these results provide a basis for drawing conclusions about the etiology of homicidal behaviour.

Methodological Critique: The major limitation in this study is the focus on homicidal behaviour which is not only very rare but a very extreme type of violent behaviour. Despite their limited focus, the authors compare their results to studies of criminal behaviour in general and criminal behaviour among inpatient populations. Given that their study focussed on outpatients, it is not clear how such comparisons could be informative. The high proportion of females in the study population (60%), may account for the lower rate of homicide in this study compared to other research, as females tend to have a lower incidence of violent crime. In addition, given that the psychometric properties of the instruments used were not reported, conclusions regarding the reliability and validity of the findings are limited. In addition, in light of the sensitivity of the information collected, the use of a self-report instrument may underestimate homicidal tendencies in this study group. Because the study focussed on outpatients receiving treatment, findings cannot be used to examine the possibility that there is an etiological relationship between mental illness and violence.

Causality: A causal inference cannot be made on the basis of these findings.

Binder, R. McNeil, E. and Binder, R.L. (1988). Effects of diagnosis and context on dangerousness. American Journal of Psychiatry, 145(6), 728-732.

Purpose and Objective: The purpose of this study was to address the following questions: (1) Are schizophrenic patients, manic patients, or patients with other diagnoses more likely to be assaultive before admission?; and (2) are schizophrenic patients, manic patients or patients with other diagnoses most likely to be assaultive during the acute phase of hospitalization?

Research Design: The authors fail to identify the study design. It appears that they conducted a longitudinal chart review.

Setting: A locked short-term inpatient psychiatric unit in a university hospital.

Study Subjects: Subjects were 150 patients randomly selected from all patients admitted during 1983 (N = 238) and during the first 6 months of 1984 (N = 118). Multiple admissions were removed.

Measures: Pre-admission violence was defined as occurring in the two week period before hospitalization. Hospital violence was measured during the first 24 hours of hospitalization. Violent behaviour was rated on a scale which included four categories: (1) attacks on persons; (2) attacks on objects; (3) threats to attack persons; and (4) verbal attacks on persons.

Main Findings: No statistically significant differences in ethnicity or social class were found. The data showed that 21% of the patients had attacked persons and 25.3% had engaged in fear-inducing behaviour during the 2 weeks before admission. Chi-square analysis revealed a significant association between diagnosis and the occurrence  of violence, specifically schizophrenic and mania. Thirteen percent of patients attacked persons during their admission and 32% engaged in fear-inducing behaviour. A significant association between diagnosis and violence surfaced; however in this case, patients with mania were most likely to attack persons while patients with schizophrenia were most likely to engage in fear-inducing behaviour.

Conclusions: The risk of violence by different diagnostic groups was found to vary according to context. Prior to hospitalization both manic and schizophrenic patients had a higher risk of assaultive behaviour than patients with other diagnoses. However, during hospitalization, manic patients were more likely to be assaultive. During the first 24 hours of hospitalization, schizophrenic patients are given neuroleptics, which decrease psychotic symptoms and causes sedation and decreases the likelihood of violence.

Methodological Critique: The diagnostic groups compared displayed different demographic characteristics. These may have accounted for some of the differences in violence noted.

Causality: A causal inference cannot be made on the basis of these findings.

Buckley, P., Walshe, D., Colohan, H.A., O’Callaghan, E., Mulvey, F., Gibson, T., Waddington, J.L. and Conall, L. (1990). Violence and schizophrenia - a study of the occurrence and clinical correlates of violence among schizophrenic patients. Irish Journal of Psychological Medicine, 7, 102-108.

Purpose and Objective: The purpose of this study was to explore the characteristics of violent behaviour and its clinical correlates among psychiatric inpatients.

Research Design: Data were collected through a chart review. Although the authors do not specify the design, data collection procedures are consistent with a retrospective survey design.

Setting: Psychiatric inpatient department in a general hospital in Stillorgan, Dublin.

Study Subjects: The sample consisted of all patients (N = 698) with an International Classification of Diseases Ninth Edition (ICD-9) diagnosis of schizophrenia. Subjects were admitted between 1983 and 1988.

Measures: Violence was defined as either physical assault or deliberate damage to property. Violence was recorded in both the community and hospital setting. Any act occurring since the onset of the patient’s illness was included.

Main Findings: Of the 698 schizophrenic patients reviewed, 113 (16.2%) had engaged in acts of violence. Patients who had been violent were compared to patients with no history of violence. The two groups were indistinguishable in terms of the presence or absence of positive and negative symptomatology, family history of psychiatric illness, or treated depression. Male patients  displayed a higher rate of violence than their female counterparts. Sufficient data were available to characterize 111 patients (out of 113) with respect to their violent acts. Twenty (18%) had been violent in hospital, 62 (56%) in the community and 29 (26%) in both settings. Most of the incidents of community violence occurred in the home and involved episodes of damage to furniture or assault on relatives. Most of the assaultive behaviour was minor.

Conclusions: The majority of violent acts were of a minor nature and seldom resulted in serious physical injury.

Methodological Critique: The authors stated that these finding are comparable to earlier research findings. The authors recognized two potential sources of sampling bias. Firstly, patients with a milder illness who were treated only as outpatients were excluded from consideration. This may have resulted in an overestimation of violence among schizophrenic patients. Secondly, patients who displayed persistent and severe violent behaviour were excluded since they were referred for treatment to regional secure units. In addition to the biases identified by the authors, it is probable that reliance on nursing notes may have underestimated violence.

Causality: A causal inference cannot be made on the basis of these findings.

Cirincione, C., Steadman, H.J., Clark-Robbins, P. and Monahan, J. (1992). Schizophrenia as a contingent risk factor for criminal violence. International Journal of Law and Psychiatry, 15, 347-358.

Purpose and Objective: This study assessed the extent to which a diagnosis of schizophrenia was predictive of criminal violence after controlling for the effects of arrest history.

Research Design: The authors failed to identify the type of research design. However, based on the data collection description, it appears that a retrospective cohort design was used.

Setting: New York State Office of Mental Health Civil Facility, New York, United States of America.

Study Subjects: The two study cohorts were adult males admitted to a New York State Office of Mental Health civil facility in 1968 and 1978. The samples included both voluntary and involuntary patients. The original sample was 400. However including only: (1) those patients under the age of 50; (2) those patients with complete records; (3) those with a DSM-III-R psychiatric disorder (excluding personality disorders) and; (4) those patients who had been released within 5 years of their target admission, the final sample sizes of the 1968 and 1978 cohort consisted of 255 and 327, respectively. The majority of the cases, 86.7% had a primary diagnosis of either schizophrenia or substance abuse.

Measures: Information was collected on each patient’s diagnosis at target admission, age at admission, race, and prior arrest history. Data on subsequent arrests  was collected from the New York State Division of Criminal Justice Services for 11 years after inpatient admission. Violent crime was considered to be murder, manslaughter, rape, attempted rape, assault, kidnapping and sodomy.

Main Findings: For the 1968 cohort, the only variable significantly related to subsequent violence was prior arrest history. In the later cohort, prior arrest history was again significantly related to subsequent violence. Additionally, persons who were non-Caucasian were significantly more likely to be violent than Caucasians.

Of those diagnosed with schizophrenia and having no arrests, 10.7% were subsequently violent compared to 2.2% of those with substance abuse disorders. In the 1968 cohort, the probability of arrest for a violent crime was highest for persons with schizophrenia and lowest for patients in the other diagnostic category. For the 1978 cohort, diagnosis did not add significantly to the prediction of violence.

Conclusions: The results produced a number of interesting patterns between diagnosis and subsequent arrests for violent crimes that did not change even when controlling for age, race, and legal status. In the 1968 cohort, diagnosis was a significant predictor of violence. The results for the 1978 cohort were the opposite of those in the 1968 cohort where, for those without a previous arrest, diagnosis was not a significant predictor of violence. In this cohort, the base rate of violence for patients with no prior arrests may have been too low (2.6%) to allow for meaningful analysis. The findings suggest caution in accepting the claim that risk assessment can and should only be made when extensive prior histories of violence are present. The results also revealed that the relationship between diagnosis and violent crimes depended upon prior arrest history.

Methodological Critique: The low base rate in the 1978 cohort and the small number of non-schizophrenic patients renders the interpretation of the statistical analyses problematic. The finding that patients with a diagnosis of schizophrenia are involved in violent incidents may be simply a result of an overrepresentation of persons with schizophrenia in this hospital population relative to other diagnostic groups.

Causality: A causal inference cannot be made on the basis of these findings.

Convit, A., Isay, D., Otis, D. and Volavka, J. (1990). Characteristics of repeatedly assaultive psychiatric inpatients. Hospital and Community Psychiatry, 41(10), 1112-1115.

Purpose and Objective: The purpose of this study was to compare patients who were repeatedly violent recidivists with those who had been violent only once or twice (non-recidivists) in an attempt to uncover correlations that were more specific to violence.

Research Design: Although the researchers  failed to specify the type of study design, the data collection procedure was consistent with a retrospective cohort study.

Setting: A large state hospital in New York City, New York, United States of America.

Study Subjects: All patients in the hospital on the first day of the study and all subsequent new admissions over the six-month study period were considered at risk for violence and therefore were included in the at-risk population. The study population included 1,195 patients who were hospitalized when the study began and 357 patients who were admitted during the six-month study period, making a total at-risk population of 1,552 patients (1,041 men and 511 women).

Measures: Incident reports were used to determine occurrences of violence. In New York state psychiatric hospitals, two types of violent behaviour warranted an incident report: fights and assaults. A fight was defined as a physical altercation between two patients. An assault was defined as a physical attack by a patient in which the victim did not strike back. For this study all the incident reports for fights and assaults over the six-month period were collected. Patients who were involved in three or more such incidents were defined as recidivists.

Main Findings: During the study period, 4907 separate incidents of violent behaviour occurred, including 174 fights (35%), 233 assaults on patients (47%), and 90 assaults on staff (18%). A total of 313 different patients (201 men and 112 women) or 20% were involved in a fight or were the attacker in an assault one or more times during the six month-study. Seventy of the 313 violent patients (31 men and 39 women) met the definition of recidivism. These 70 patients accounted for 53% of all the instances of violent behaviour. The percentage of women classified as recidivist was significantly higher than that of men. While women recidivists tended to be younger, there were no significant diagnostic differences between the recidivists and non-recidivists.

Conclusions: The data from this study demonstrated that approximately 5% of the at-risk patient population were responsible for 53% of the assaults. Eight percent of the women in the hospital accounted for 70% of the assaults committed by women and 3% of the men accounted for 40% of the assaults perpetrated by men. The findings indicate that a small percentage of patients are responsible for about half of the violence in psychiatric hospitals. More importantly, they are responsible for more than half of the serious injuries.

Methodological Critique: The reliance on incident reports may have underestimated the level of violence in this population. The finding that a small proportion of the population is responsible for a large proportion of the violence is consistent with more general criminality studies. However, because this study focused on hospitalized patients, it cannot be generalized to all  persons with mental illness and therefore do not shed light on the etiological relationship of mental illness and violence.

Causality: A causal inference cannot be made on the basis of these findings.

Cuffel, B.J., Shumway, M, Chouljian, T.L. and Macdonald, T. (1994). A longitudinal study of substance use and community violence in schizophrenia. The Journal of Nervous and Mental Disease, 182(12), 704-708.

Purpose and Objective: This study was designed to address two questions: (1) whether substance use in schizophrenia could be cross-sectionally related to the occurrence of violent behaviour; and (2) whether substance use in schizophrenia could predict the occurrence of future violent behaviour.

Research Design: A retrospective record review was used to collect secondary data reported and documented during the course of randomized controlled trials.

Setting: A schizophrenia research clinic at San Francisco General Hospital, San Francisco, United States of America.

Study Subjects: Study subjects were 103 psychiatric outpatients who were between the ages of 18-55 years and received care between 1985 and 1989. All subjects were participants in a clinical trial of pharmacological interventions which excluded individuals with extensive legal histories or those dependent on alcohol or drugs. At 6 months, 89 patients remained in the study. Beyond 6 months, sample attrition made statistical analyses too imprecise.

Measures: All data were collected using a retrospective chart review. Study subjects had a DSM-III-R clinical diagnosis of schizophrenia, schizoaffective disorder or schizophreniform disorder recorded on their charts. These diagnoses were initially made using a Structured Clinical Interview. Violent behaviour that was recorded on the clinical file between 1-3 months and between months 3-6 comprised the main dependent measures. These included verbal threats to harm others, non-verbal threats to harm others, physical assaults, altercations, brandishing a weapon, using a weapon, starting a fire, and destroying property. Substance abuse was recorded separately for alcohol, marijuana, opiate, sedative, and hallucinogen use. Subjects were classified into those who used only alcohol or marijuana (N=9) and those using some other substance (N=11). Age, sex, and minority status were considered to be covariates in the analysis.

Main Findings: During the first 3 months, 8.6% of subjects were identified as having used alcohol or marijuana and 10.6% were found to have patterns of use of more than one substance (polysubstance abuse). During the 3-6 month period of the study, these proportions were 11.3% and 5.7%, respectively. Violent behaviour was recorded in 18.4% of the sample in months 1-3, and 14.7% in months 3-6. Polysubstance abusers were reported to be 12.56 times (p  .01) more likely to commit a violent act in the first 3 months of follow-up and 4.61 times (p .10) more likely to commit a violent act during the second 3 months of follow-up. No other statistically noteworthy relationships were reported.

Conclusions: The authors conclude that the results from this study provide “presumptive evidence” that use of some substances may predispose individuals with schizophrenia and polysubstance use to later episodes of violent behaviour.

Methodological Critique: The restricted nature of the sample, the small sample sizes and the lack of reported confidence intervals make the importance of these findings difficult to judge.

Causality: This study does not address the question of whether persons with schizophrenia are at higher risk of violence than those without a mental disorder. Thus, results cannot be used to make any causal inferences about mental disorder and violence.

Durbin, J.R., Pasewark, R.A. and Albers, D. (1977). Criminality and mental illness: A study of arrest rates in a rural state. American Journal of Psychiatry, 124(1), 80-83.

Purpose and Objective: This study examined cumulative arrests for ex-psychiatric patients and compared these to the general population.

Research Design: The authors do not name a design but data collection procedures are consistent with a historical cohort with variable follow-up spanning up to 10 years.

Setting: Wyoming, United States of America.

Study Subjects: Study subjects were 461 persons aged 18-64 years admitted to the Wyoming State Hospital during the 1969 calendar year. Excluded from the study were admissions resulting from forensic/court remands for psychiatric assessment, persons transferred to other institutions during the course of the study, and those who died while in hospital. The Wyoming State Hospital is the only psychiatric facility in the state, therefore, findings are generalizable to the population of psychiatric patients in Wyoming.

Measures: Criminal arrest data were obtained for the period 1964-1973 for the study cohort (based on fingerprint match) and for the state population.

Main Findings: Findings show different arrest patterns among male and female patients. Overall, male ex-patients were more likely to be arrested and women were as likely to be arrested as the general population. A small number of male patients were responsible for the bulk of arrests in this group: 7.3% of the patients were responsible for 68.2% of the arrests. Male patients appear to have higher rates for violent crimes compared to the general population in most crime categories. However, men diagnosed with personality disorder or drug dependence contributed disproportionately to arrests. Persons with  personality disorder comprised 10.1% of the cohort but 25% of the arrests and those with drug dependence accounted for 3.5% of the patients but 7.9% of the arrests. Persons with schizophrenia were not overly represented in the arrest records and none of the arrests were for crimes against people.

Conclusions: The authors indicate that definite conclusions and generalizations from this type of research are risky because of the multitude of factors that influence arrest rates. Findings were interpreted to suggest that mental patients were not arrested less frequently than the general population, as some previous research had suggested.

Methodological Critique: This study corrected for the fact that patients were not at risk for arrest while they were institutionalized. The different rates of arrest noted for men and women highlights the importance of controlling for demographic differences when comparing to general population data.

Causality: Given the selected nature of the study cohort, findings cannot be interpreted to reflect an causal relationship between mental illness and violence.

Fottrell, E. (1980). A study of violent behaviour among patients in psychiatric hospitals. British Journal of Psychiatry, 136, 216-221.

Purpose and Objective: The purpose of this study was to examine violent behaviour among patients in British psychiatric hospitals.

Research Design: The researchers do not specify what design was employed. It appears to be case-control given that subjects were recruited into the study based on the occurrence of a violent incident.

Setting: The study was carried out in Tooting Bec Hospital in London, the Chiltern Psychiatric Wing of Sutton General Hospital in Sutton, and Park Prewett Hospital, in Basingstoke, Hants. At the first and second hospital, the study continued for one year and covered the total patient population. In the third hospital, the study occurred over a four month period.

Study Subjects: Both Tooting Bec and Park Prewett hospitals had populations of approximately 1100 patients at the time of the study.

Measures: The type of violence studied was intentional personal physical violence, including that to the self. Three degrees of violence were identified. Violence of the first degree was present when no physical injury was detectable or suspected in the victim when examined by the doctor. Second degree violence was when minor physical injuries were present. The third degree included incidents where physical injury was found or suspected in the victim. A questionnaire was developed to capture occurrences of violence.

Main Findings: More younger age groups and females were responsible for the violent incidents. Schizophrenia was the most common diagnosis among the  offending patients. Only a small percentage of the total patient populations behaved violently and a smaller percentage of patients were responsible for a large percentage of the incidents.

Conclusions: While incidents of petty violence occur in psychiatric hospitals, serious assaults are rare. The three serious incidents which occurred were suicide. The authors concluded that in these hospitals one is at much greater risk of dying by one’s own hand than by the hand of another.

Methodological Critique: Because results were based on patient samples, they cannot be used to infer violence to non-hospitalized persons with mental illness. Nevertheless, it is interesting to note that the incidence of violence was considered to be low in a group that would be expected to be at higher risk of violence. This could be due to under-detection.

Causality: A causal inference cannot be made on the basis of these findings.

Grossman L.S., Haywood T.W., Cavanaugh J.L., Davis J.M. and Lewis D.A. (1995). State psychiatric hospital patients with past arrests for violent crimes. Psychiatric Services, 46(8), 790-795.

Purpose and Objective: To compare the prevalence of criminality and violent crime among four groups of patients: patients diagnosed with schizophrenia; schizoaffective disorder; bipolar affective disorder; and unipolar affective disorder.

Research Design: Review of arrest records of hospitalized mental patients.

Setting: Four state psychiatric hospitals in Illinois, United States of America.

Study Subjects: Study subjects were 172 inpatients who were interviewed during their voluntary hospitalizations as part of a longitudinal research program. These individuals were identified from a random sample of 313 patients as meeting the study’s diagnostic inclusion criteria.

Measures: Patients were diagnosed with the RDC (Research Diagnostic Criteria) and DSM-III, and selected via the Schedule for Affective Disorders and Schizophrenia (SADS). Criminal history was determined based on arrest records from the Chicago Police Department. Patients were classified according to the most violent crime for which they were arrested prior to hospitalization.

Main Findings: Of the 172 study subjects, 63.5% had no prior criminal history, 3% had committed only non-violent crimes, 6.5% had committed crimes against property, and 27% had committed crimes of violence. A significant association between diagnostic category and past crimes of violence was found. Patients with schizoaffective disorders were more likely to have been arrested for a violent offense. Patients who were considered to be psychotic during their hospitalization were significantly  more likely to have a history of violent crime than non-psychotic patients. Comparing only patients with paranoid schizophrenia to those with non-paranoid schizophrenia, those with paranoia were significantly more likely to have committed a violent crime. In addition, patients who abused drugs or both drugs and alcohol committed more serious crimes. Finally, past history of violent crime was more common among male patients from minority groups.

Conclusions: Demographic features, a diagnosis of schizoaffective disorder, psychosis, paranoid symptoms, and substance abuse may all be associated with violent behaviour.

Methodological Critique: It is not clear whether patients were symptomatic at the time of their arrests, or whether their psychiatric illness predated their criminality.

Causality: The highly selected sample of psychiatric inpatients and the lack of temporal ordering of study factors makes it impossible to draw general statements of causality from these findings.

Guze, S.B., Woodruff, R.A. and Clayton, P.J. (1974). Psychiatric disorders and criminality. Journal of the American Medical Association, 227(6), 641-642.

Purpose and Objective: The purpose of this study was to address the question, “What kinds of psychiatric disorders are associated with criminality?”

Research Design: Although the authors did not specify, the data collection procedure is consistent with a retrospective survey design.

Setting: The authors did not indicate the study setting.

Study Subjects: A sample of 500 patients of a psychiatric clinic population.

Measures: Data was collected from a chart review describing the results of an interview that had been previously conducted. This interview included a section dealing with “trouble with police”or imprisonment.

Main Findings: Twenty-two patients had a history of at least one felony conviction (4%). A significant difference was found between men and women. Six of the 22 patients, all men, were convicted because of behaviour resulting from sexual deviation. Five of these men had no other psychiatric diagnosis. Fourteen of the remaining 16 patients were either sociopathic (N = 13), alcoholic (N = 8) and/or drug dependant (N = 3). None of the patients with either schizophrenia or primary affective disorder reported a felony conviction.

Conclusions: Results are consistent with those previously obtained from studies of convicted felons. Sociopathy, alcoholism, and drug dependence were the principle psychiatric disorders associated with serious crime. These findings suggest that psychiatrists must deal chiefly with sociopathy, alcoholism, and drug-dependence in order to prevent and treat criminality.

Methodological Critique: Misclassification bias is the major threat to the internal validity of this study. Relying on self-report measures for assessing criminal behaviour increases the chances of underreporting. Findings must be interpreted as limited to psychiatric patients.

Causality: A causal inference cannot be made on the basis of these findings.

Holcomb, W.R. and Ahr, P. R. (1988). Arrest rates among young adult psychiatric patients treated in inpatient and outpatient settings. Hospital and Community Psychiatry, 39(1), 52-57.

Purpose or Objective: The purpose of this study was to determine the prevalence of criminal behaviour among a statewide sample of young adult patients with major psychiatric diagnoses who were treated in both outpatient and inpatient settings, and to identify factors contributing to arrests.

Research Design: Although the authors did not specify, the data collection procedures are consistent with a retrospective cohort design.

Setting: Inpatient, outpatient, and community residential care settings in Missouri, United States of America.

Study Subjects: Subjects were a random sample of 611 young adult patients from a total of 32,000 who: (1) had one of five major diagnoses (drug or alcohol abuse, schizophrenia or other psychosis, major affective disorder, personality disorder, organic brain syndrome); (2) were between the ages of 18 and 35 years; and (3) received services during 1982. At last contact with a clinician, 51% were inpatients, 47% were outpatients and 1.7% were admitted to community residential facilities. The average number of prior psychiatric inpatient admissions was 3.27.

Measures: The Missouri Highway Patrol Department was used to collect information on history of arrests. This database included a record of arrests within the state and from all other states. Arrests for violent arrests were distinguished from non-violent arrests. Level of functioning was assessed by the clinician at last contact. Ratings were obtained for 327 (53%) of the total sample.

Main Findings: Thirty-eight percent of the sample were arrested at least once as adults. The data showed that 19% of the sample committed only non-violent crimes, 4.4% committed violent crimes, and 14.5% committed both. Significant differences were found by diagnosis. Patients diagnosed with alcohol or drug abuse were more likely to be arrested for crimes. There were no statistical differences in the association between diagnosis and violent crimes. The relationships of various demographic and mental health variables to the 13 specific arrests categories were examined with correlation coefficients. Few significant relationships emerged.

Conclusions: The authors concluded that the  restriction to young adults (18-35) and the inclusion of outpatients probably underestimated the lifetime prevalence of arrests. The authors argued that public mental health and criminal justice administrators must put a high priority on programs to address the needs of this young adult group. The authors claimed that the arrest rate for their sample was 17 times greater than the arrest rate for the same-aged general population.

Methodological Critique: There was a problem with missing data. Level of functioning was assessed at last contact from the clinician but only 53% of the clinicians were able to complete the study form. A further 167 forms were sent back incomplete because the clinician could not recall the patient. In addition, 62 forms were returned because the clinician was no longer employed at the facility, and 55 forms were not returned. This level of missing data is unacceptable and makes the findings uninterpretable. Even the forms that were returned relied on the clinician’s memory and it is unclear whether the clinician would have classified patients correctly. Finally, an excessively large number of statistical comparisons were conducted with the result that the few significant ones are difficult to interpret because they could have occurred by chance alone.

Causality: A causal inference cannot be made on the basis of these findings.

Kennedy, M.G. (1993). Relationship between psychiatric diagnosis and patient aggression. Issues in Mental Health Nursing, 14, 263-273.

Purpose and Objective: The purpose of this study was to examine the relationship between psychiatric diagnosis and patient aggression within the context of routine intrahospital relocation.

Research Design: This study was a secondary analysis of existing data. While the authors fail to mention the study design, the data collection procedure is consistent with a historical follow-up study.

Setting: The original research was conducted at a large state hospital in the Pacific Northwest, United States of America. At the time of the study, there were over 1,000 patients in residence, with an average of 250 admissions per month.

Study Subjects: The records of 201 patients admitted over a five-month period were selected for review. Subjects ranged in age from 19 to 96 years. There were 108 (53.7%) males and 93 (46.3%) females. Caucasians made up 93.5% of the sample. The number of previous admissions to the state hospital ranged from one to 22 (mean = 3.4).

Measures: Data from patient records were collected using an adaptation of the Overt Aggression Scale (OAS). The OAS divides aggressive behaviour into four categories: verbal aggression; physical aggression against objects; physical aggression against self; and physical aggression against other people. Inter-rater reliability of the adapted OAS was tested by having a second rater use the  same scale to rate 28 of the 201 patient records. A Pearson Correlation of .77 was obtained between the two raters indicating good interrater reliability.

Main Findings: The total number of aggressive incidents recorded for the sample was 2,555. The majority of these were categorized as verbal aggression and physical aggression against other people. No significant differences were noted among DSM-III diagnoses in total patient aggression or the individual scale scores of physical aggression toward self, objects, or verbal aggression. The only significant difference noted was between individuals diagnosed with paranoid schizophrenia in the category of physical aggression toward other people.

Conclusions: There are different kinds of patient aggression. The way in which this behaviour is expressed is only partly related to diagnosis. Given that not all aggressive behaviours were the same, different interventions may be needed, depending on the behaviour expressed.

Methodological Critique: As most patients were admitted involuntarily, the generalizability of findings are quite limited.

Causality: A causal inference cannot be made on the basis of such a selected sample.

Klassen, D. and O’Connor, W. A. (1988). Crime, inpatient admissions, and violence among male mental patients. International Journal of Law and Psychiatry, 11, 305-312.

See also: Klassen, D. and O’Connor, W.A. (1988). Predicting violence in schizophrenic and non-schizophrenic patients: A prospective study. Journal of Community Psychology, 16, 217-227 and Klassen, D. and O’Connor, W.A. (1988). A prospective study of predictors of violence in adult male mental health admissions. Law and Human Behaviour, 12, 143-158.

Purpose and Objective: This study examined the relationship between hospitalizations, arrests, and violence in a sample of adult male patients whose admitting complaints suggested risk for violent behaviour. The objective of this study was to make comparisons between mental patients and their demographic peers, that is, young, male, minority, and low socio-economic status individuals.

Research Design: Although the authors do not indicate the study design, the data collection is consistent with a longitudinal follow-up of a case series. Arrests and admission histories were obtained from existing records, and subsequent arrests and admissions were obtained for a one-year follow-up period post-release.

Setting: An urban community health centre in Kansas City, Missouri, United States of America.

Study Subjects: The sample consisted of 304 adult males admitted as inpatients to an urban community mental health centre. They represented 91% of all patients selected. Only those men who had a history of violent  behaviour or indications of violence in the presenting problem were included in the study.

Measures: Arrest data were obtained from the Kansas City, Missouri Police Department and covered the greater Kansas City area as well as outlying counties in Western Missouri and Eastern Kansas. Inpatient admission data were obtained from the mental health centre’s records.

Main Findings: The data showed a strong positive association between previous arrests and previous admissions. The authors reported that prior arrests and prior admissions were associated with subsequent violence. The best predictor of arrests during the follow-up period was the number of prior arrests. Diagnosis of substance abuse and number of prior admissions were also statistically significant in predicting arrests. Arrests for violence were predicted by a diagnosis of substance abuse, prior arrests for violent crimes, and age. Admissions for violence were predicted by number of prior admissions and age at first admission.

Conclusions: The authors concluded that arrests and hospital admissions were highly correlated in this sample, both prior to admission and after discharge. Furthermore, subsequent arrests were predicted by prior admissions controlling for the effects of prior arrests. The authors recognized that the nature of this data does not permit the conclusion of an association between crime and mental disorder.

Methodological Critique: Only men who had a history of violent behaviour or indications of violence in the presenting problem were included in the study. Therefore, it is not surprising that the sample as a whole had high rates of violent recidivism.

Causality: A causal inference cannot be made on the basis of these findings.

Lafave, H.G., Pinkney, A.A. and Gerber, G.J. (1993). Criminal activity by psychiatric clients after hospital discharge. Hospital and Community Psychiatry, 44(2), 180-181.

Purpose and Objective: The authors studied arrest rates for psychiatric rehabilitation patients discharged to the community after lengthy hospitalization.

Research Design: Prospective follow-up study with a one year follow-up period.

Setting: Brockville Psychiatric Hospital, Brockville, Ontario, Canada.

Study Subjects: Study subjects comprised 55 of 67 patients discharged from the Brockville Psychiatric Hospital between 1986 and 1988. More than two-thirds had a discharge diagnosis of schizophrenia.

Measures: Data were collected in face-to-face interviews with patients following their discharge using structured interview schedules. Ontario arrest rates were used to form the population comparisons.

Main Findings: Only 2 of the 55 patients  interviewed were charged with a criminal offense during their first year following discharge, giving an unstandardized arrest rate of 3.84 per 100 persons versus 11.35 per 100 persons for the general population.

Conclusions: The frequency of criminal charges in the study cohort was lower than expected based on general population rates for Ontario indicating that persons with a chronic mental illness, particularly schizophrenia, are not more prone to engage in criminal activities than the general population.

Methodological Critique: Although the sample size is quite small, this is an interesting study because it focuses on long-term rehabilitation patients who are presumed by other authors to be at high risk of arrest upon their re-entry into the community. A second important feature is that this study was conducted in Canada. The authors argue that availability of community mental health programs, housing, and social opportunities for released patients improves their chances of successful re-entry. Findings from this study raise an important issue. Given universal access to health care in Canada, and a different community mental health system, the relationship between mental hospital discharge and subsequent arrest noted in previous U.S. studies may not be generalizable to Canada.

Causality: Because of the selected nature of this study population, findings cannot be used to infer etiological relationships between mental illness and violence.

Lagos, J.M., Perlmutter, K. and Saexinger, H. (1977). Fear of the mentally ill: Empirical support for the common man’s response. American Journal of Psychiatry, 134(10), 1134-1137.

Purpose and Objective: The purpose of the study was to determine how frequently people behave violently when they become mentally ill.

Research Design: While the authors failed to specify the study design, the data collection procedures are consistent with a retrospective cohort design. Subjects were identified for inclusion in the study based on admission to a psychiatric facility.

Setting: Four psychiatric facilities in New Jersey, and New York State, United States of America.

Study Subjects: One hundred records of patients admitted during 1974 to each of four psychiatric facilities were randomly selected.

Measures: Admission notes for 400 patients were reviewed for any description of patient behaviour that might be construed to be violent.

Main Findings: Results revealed that 37.7% of the 400 admissions sampled manifested some form of violent behaviour prior to admission. Twenty percent of the sample were specifically described as acting in a physically violent way toward persons or objects, and another 11% were described as acting violent but in vague terms.

Conclusions: The authors concluded that by  broadening the scope to include less serious acts of violence, approximately 36% of 321 psychiatric admissions were preceded by some form of violent fear-inducing behaviour. According to the authors, evidence suggests some factual basis for fearing the mentally ill.

Methodological Critique: Given that dangerousness is one of the criteria for hospitalization, it is not surprising that a large number of hospitalized patients have exhibited violence just prior to their admission. Because these findings focus on a violent-prone group, they do not support the conclusion that mentally ill, in general, are prone to violence.

Causality: A causal inference cannot be made on the basis of these findings.

Lindelius, R. and Salum, I. (1973). Alcoholism and criminality. Acta Psychiatrica Scandinavica, 49, 306-314.

Purpose and Objective: To study the relationship between the frequency of criminality and the severity of alcoholism.

Research Design: A consecutive series of patients were studied. Criminality was compared among three groups of alcoholics classified according to severity.

Setting: A special ward for the treatment of alcoholism at a general hospital in a large metropolitan area in Sweden.

Study Subjects: All male alcoholics (1026) admitted to the ward from 1956 to 1961.

Measures: No special measures and no mention made of type of diagnostic instrument. On the basis of clinical manifestations, patients were classified to one of the three groups. Information on criminality was obtained from the General Criminal Register.

Main Findings: More subjects in the low severity group were registered as criminals (45%) than those in the most severe group (30%). Younger alcoholics, below age 40, had a higher risk of being involved in criminality. Most offenses involved property or driving under the influence.

Conclusions: There is no simple relation between alcohol and criminality. Other factors, such as age or personality deviations, may be as important.

Methodological Critique: The main strength of this study is the correlation of criminal activity to levels of severity of alcoholism. However, the study is a case series of individuals admitted to a special unit because of their alcohol problem. Hence this is a highly selected sample with no comparison groups and the diagnostic approach is not specified. It is not clear whether other factors could be accounting for the study findings.

Causality: A causal inference cannot be made on the basis of these findings.

Lindqvist, P. and Allebeck, P. (1990). Schizophrenia and crime: A longitudinal follow-up of 644 schizophrenics in Stockholm. British Journal of Psychiatry,  157, 345-350.

Purpose and Objective: The main goals of this study were to determine if persons with schizophrenia commit crimes more frequently than the general population and if so, to what extent, and to describe the types of crimes committed by schizophrenic patients, compared to the general Swedish population.

Research Design: Historical cohort design with a fifteen year variable follow-up period.

Setting: Stockholm, Sweden.

Study Subjects: Subjects were 644 persons with schizophrenia diagnosed according to ICD-8 who had been discharged from inpatient psychiatric facilities in Stockholm county during 1971.

Measures: Both measures of schizophrenia and criminal activity were obtained from central registry data. The authors have estimated that 85% of their ICD-8 diagnoses meet DSM-III criteria. Files were linked via a unique personal identification number that is given to all Swedish subjects and follows them from birth to death. Criminal activity was measured by ‘principal offenses’ committed during one year. The principal offense corresponds to the most severe penalty, but it is not clear whether this corresponds to an arrest or a conviction. Appropriate statistical analyses were used to account for the variable follow-up (e.g. rates per person years of observation) and rates were age- and sex- standardized to the population for comparison purposes. Given that socio-economic status is a likely intervening variable in the disease process, it was not controlled.

Main Findings: The crime rate among women was twice that expected whereas the crime rate among men was similar to the general population. Thirteen percent of the violent offenders were women (4 of 32) whereas the corresponding general population figure was 5%-10%. Assault was the most common violent offense committed and the most serious crime recorded was aggravated assault. The study cohort committed four times as many violent crimes as the general population. Given small numbers, these were not analyzed by age or sex.

Conclusions: Although discharged schizophrenic patients did not, in general, commit more crimes than the general population, they did commit four times as many violent crimes.

Methodological Critique: It is not clear whether the principal offenses of the study cohort were compared to principal offenses in the general population, or whether they were compared to the general population crime rates. As principal offenses measure only the most serious crimes recorded in any given year, a comparison based on the crime rate (all offenses recorded) would bias findings toward finding no effect. Therefore, findings from this study may reflect a conservative estimate of the difference between the criminal activity of the study cohort compared to the general population. Because of small numbers,  findings for violent crimes were not standardized to the population for age and sex, thus, there could have been confounding by these factors.

Causality: Because the study focused on criminal activity among discharged patients, findings cannot be interpreted to reflect causal inferences regarding mental illness and violence among all persons with schizophrenia.

Link, B.G., Andrews, H. and Cullen, F.T. (1992). The violent and illegal behaviour of mental patients reconsidered. American Sociological Review, 57, 275-292.

This empirical study contains an excellent review of prior literature, therefore it has been summarized in some detail. Link addresses the question of whether stereotypical portrayals of persons with mental illness as dangerous are correct by reviewing empirical literature on the criminality of former mental patients. He notes that early studies tended to find no difference between cohorts of mental patients and the general population with respect to criminality, while more recent studies have indicated that former mental patients have significantly higher criminality. The authors indicate that the strength and consistency of more recent findings suggests a causal mechanism and suggests that active psychosis is a likely factor to be considered. Studies have demonstrated that the crimes committed by persons with mental illness are often in response to hallucinations or delusions. Previous research indicates that 20% to 40% of crimes may be directly motivated by psychosis. These findings are supported by studies of violent behaviour in mental hospitals which find that the active phases of psychoses are the periods of greatest risk.

Link then identifies several alternative explanations for these findings. The process of criminalization may result in mentally ill persons being shunted into the criminal justice system. Or, mentally ill persons receiving treatment may be a sub-group of the mentally ill who may be at higher risk of criminality by virtue of other socio-cultural factors. No arrest rate studies to date have successfully connected the higher arrest rates among mentally ill samples to symptoms of mental illness. Thus, it is not known whether higher rates of crime and violent crime noted among mentally ill samples are a function of the mental illness or other non-causal influences. It is also possible that deviance has been medicalized and that the high rates of criminality among mentally ill is a result of this broader trend. This is consistent with findings from studies showing higher proportions of persons in psychiatric hospitals with prior histories of arrest.

Purpose and Objective: This study was designed to address the question of whether former mental patients have higher rates of violent and illegal behaviour than non-patients and whether any differences noted could be explained by factors other than mental illness.

Research Design: Cross sectional surveys  conducted in 1979 and 1982 as part of another study.

Setting: Washington Heights section of New York City, United States of America.

Study Subjects: Study subjects were 521 randomly selected community residents and 232 patients recruited from outpatient psychiatric clinics and inpatient services located in the Washington Heights neighbourhood. Patients who were not neighbourhood residents were excluded. Four groups were constructed for analysis: first treatment contact patients; repeat treatment contact patients; former patients; and never-treated community residents.

Measures: Patients were defined on the basis of their admission to a local facility and DSM-III diagnoses were retained for descriptive purposes. Sixty-three percent had major mental illnesses characterized by psychotic symptomatology (depressive disorders, schizophrenia, or other psychotic disorders). Official arrest data were obtained as well as self-report data concerning arrests, hitting others, fighting, weapon use, and hurting someone badly. Census data were also used to describe the socio-demographic context of the community. First treatment reflected first treatment within the year prior to the interview (for community residents), or first-ever contact with the clinic at the time of study. Psychotic symptoms were measured using a standardized scale.

Main Findings: Former mental patients scored higher on official measures of arrest as well as self-reports of violence compared to community controls. Within the patient group, violence was associated with psychotic symptoms.

Conclusions: The authors conclude that assertions that mental patients and former mental patients are on average no more violent than non-patients is incorrect even when socio-demographic and community context variables are controlled. But, the excess risk posed by patients is modest and only apparent among patients with current psychotic symptoms.

Methodological Critique: The statistical analysis is technical and highly complex, and is not presented in a user-friendly manner. For example, logistic regression coefficients and standard errors are presented without an attempt to translate these into odds ratios and 95% confidence intervals which may be more easily understood.

The authors provide evidence that persons receiving treatment for mental illness are at higher risk of being violent than non-patients. Given that treatment services are oriented toward a dangerousness standard, this finding is not surprising. Because the study was cross-sectional, temporal ordering of factors could not be established. The authors ask the reader to dismiss the possibility of reverse-causation because their results are consistent with prospective studies of former mental patients in which temporal ordering of factors has been  clearly established. This is not warranted as prior prospective studies have not purified their study cohorts to ensure that persons with prior histories of violence are excluded. Given that prior arrests/violence are known to predict future arrests/violence, temporal ordering of factors remains a thorny issue that cannot be so easily dismissed.

Causality: Because former mental patients are known to comprise a sub-group of mentally ill that are more prone to violence, this study cannot be used to arrive at a causal determination of whether the mentally ill in the community are more dangerous and violent than the non-mentally ill.

Lundy, M.S., Pfohl, B.M. and Kuperman, S. (1993). Adult criminality among formerly hospitalized child psychiatric patients. Journal of the American Academy of Child and Adolescent Psychiatry, 32(3), 568-576.

Purpose and Objective: The goal of this study was to investigate risk factors for adult criminality among children who required psychiatric hospitalization at a relatively young age.

Research Design: A case-control design was used. Cases were defined as 23 individuals known to have an adult prison record and controls were 115 males who had no prison record. All of the cases proved to be male.

Setting: The University of Iowa Psychiatric Hospital, Iowa, United States of America.

Study Subjects: Subjects were 138 children (under the age of 12 years at discharge) who received inpatient psychiatric care between 1970 and 1982. Persons with mental retardation, defined as an IQ score of less than 70, were excluded from the study because of difficulties in obtaining informed consent from this group.

Measures: ICD-9 diagnostic categories were used to assign each child to a single, main diagnostic group: organic disorders (organic mental disorder, infantile autism, and developmental delay), attention deficit disorder, emotional disorders (affective disorder, neurotic disorder, neurotic depression, eating disorder, and personality disorder), and adjustment disorders. A miscellaneous grouping was also used. Presence or absence of an adult prison record was obtained from the Iowa Department of Corrections and was used as the main outcome of interest. Childhood risk factors were assessed via a detailed chart review. These factors included assaultive behaviour (excluding that which could be construed as developmentally normal such as altercations with peers or siblings which was not a focus of concern for the caregiver or parent), criminality in a biological parent, psychiatric illness in a biological parent, psychotropic medication use on discharge (to serve as a proxy for severity of disturbance), adoptive status, and treatment responsiveness.

Main Findings: No diagnostic category was statistically related to adult imprisonment. No statistical relationships were also found between adult imprisonment and  presence of multiple psychiatric diagnoses, adoptive status, age at index hospitalization, IQ, gap in verbal-performance IQ of more than 15 points, length of stay, multiple admissions, or parental psychiatric illness. Assaultive behaviour in childhood was associated with 5 times the risk (95% CI, 1.8 to 13.8), parental criminality (4.6 times the risk, 95% CI, 1.43 to 16.41). Race was also found to be an important predictor in a subsample of 74 for whom this information was available.

Conclusions: The authors concluded that the failure of diagnosis to predict outcome is not inconsistent with previous studies. The authors highlight the importance of childhood assaultive behaviour, in the absence of a diagnosis of conduct disorder, and parental criminality as the most important predictors of a poor outcome.

Methodological Critique: A minor difficulty with this study are the small cell sizes resulting in large confidence intervals for some comparisons and less precise estimates than would have been desired under ideal conditions.

Causality: Because all study subjects received psychiatric intervention, results cannot be used to derive a general causal explanation regarding the relationship between mental illness and violence, per se. No comparison group of non-psychiatrically ill was used. Nevertheless, it is interesting that no diagnostic category, not even conduct disorder, predicted adult criminality.

Lurigio, A.J. and Lewis, D.A. (1987). The criminal mental patient: A descriptive analysis and suggestions for future research. Criminal Justice and Behaviour, 14(2), 268-287.

Purpose and Objective: This study was designed to extend earlier findings by yielding a comprehensive and prospective look at the movement of the mentally ill within and between the criminal justice system and mental health systems with a focus on the criminality and dangerousness of patients.

Research Design: Although the authors do not specify, data collection is consistent with a longitudinal follow-up of a case-series. Current arrest and admission data were obtained along with lifelong criminal and psychiatric histories.

Setting: Chicago-area state psychiatric institutions, United States of America.

Study Subjects: A random sample of approximately 320 psychiatric patients, aged 18-65 years, was selected from a population of inpatients from Chicago-area state psychiatric institutions. Sampling was stratified on the basis of age, sex, race and previous admissions, and executed in a series of weekly waves over the course of three months.

Measures: Four sources of information pertaining to the criminality, dangerousness, and victimization experiences of the patients were used. First, the Chicago Police Department’s Bureau of Investigations  Unit’s records were searched to ascertain whether study subjects were arrested within a recent six-month calender period. Second, official police incident data were reviewed to assess the degree to which the circumstances surrounding the arrests were characterized by violent or dangerous activities. Third, official criminal histories or “rap sheets” were reviewed but only for those patient arrestees identified from the Chicago Police Department. Fourth, the authors assessed the patients’ self-reports of violent behaviour via a personal interview. Information on current admission and psychiatric history were collected through hospital charts. In addition, time at risk was estimated.

Main Findings: Based on police records, 10% of the random sample was arrested within the six-month period prior to hospitalization. Patients were involved in a total of 58 police encounters. A significantly greater percentage of arrests (60%) appeared in the aftermath of hospitalization rather than in the pre-admission stages of hospitalization. Of the 58 arrest report narratives, 50% of the encounters were characterized by an interpersonal conflict or altercation. Arrestees were compared to psychiatric patients in the general sample on a number of demographic variables. The data showed that persons aged 18-34 years who were black were over-represented in the arrested group when compared to their prevalence in the larger sample. The group of arrestees had a significantly greater number of prior admissions than the overall sample. Of those arrested, 85% of the sample possessed criminal histories ranging from 1 to 30 previous arrests. During the study’s six-month period of reference, patient arrestees were admitted to the hospital on 119 separate occasions, yielding a mean of approximately 4 hospitalizations per patient. Patient arrestees were hospitalized significantly more often than patients in the general sample.

Conclusions: The authors concluded that a relatively small percentage of released psychiatric patients are involved in criminal conduct extending beyond innocuous or “nuisance-type” activities. The patients who were likely to pass through the criminal justice system in the short six month period under investigation were those with chronic readmissions to state psychiatric facilities.

Methodological Critique: The use of arrests in this study may have underestimated the prevalence of criminality among released patients if they were diverted out of the criminal justice system to mental health treatment centres by police.

Causality: A causal inference cannot be made on the basis of these findings.

McNeil, E. and Binder, R.L. (1994). The relationship between acute psychiatric symptoms, diagnosis, and short-term risk of violence. Hospital and Community Psychiatry, 45(2), 133-137.

Purpose and Objective: This study examines the relationship between acute psychopathology and short-term risk of violence in a sample of newly hospitalized acute patients. The goal was to evaluate whether the pattern of symptoms associated with short-term risk of violence varied depending on diagnosis.

Research Design: Although not indicated, it appears that a case-control design was used.

Setting: The study was conducted on a university-based, locked, short-term psychiatric inpatient unit with a mean length of stay of 18 days.

Study Subjects: The sample consisted of 127 diagnostically heterogeneous patients admitted during 1988-1989 and 203 patients who had been admitted to the unit between 1989 and 1990. The total sample included 330 subjects. Fifty-four percent of the 330 patients were male.

Measures: The Overt Aggression Scale (OAS) was used to evaluate violent behaviour exhibited by the patients in hospital. The OAS is a widely used measure with documented reliability and validity as an index of inpatient aggression. It is a behavioural checklist that nursing staff complete at the end of each eight-hour shift to indicate if patients have engaged in physical aggression against other people, against objects, or against themselves, or have engaged in verbal aggression. The Brief Psychiatric Rating Scale (BPRS), a widely used measure of psychopathology with good interrater reliability, was used to evaluate each patient at admission.

Main Findings: Ratings on the OAS indicated that 23% of the patients engaged in physical aggression against other people during their hospitalization. Assaultive patients were over-represented in the diagnostic categories of schizophrenia, mania, and organic psychotic conditions. Compared to non-assaultive patients, patients who became assaultive had an admission mental status characterized by significantly higher levels of thinking disturbance, hostile suspiciousness, agitation, and excitement.

Conclusions: This study found an association between diagnoses such as schizophrenia, mania, and organic psychotic conditions and imminent risk of assaultive behaviour among a sample of acutely ill, newly hospitalized patients.

Methodological Critique: It is not clear whether nursing staff would be more likely to record incidents of violence in the health record of patients who appear to be most agitated with thought disturbances. Thus, it is not clear to what extent underreporting of violence in some diagnostic groups may have resulted in these findings.

Causality: A causal inference cannot be made on the basis of these findings.

Modestin, J. and Ammann, R. (1995). Mental disorders and criminal behaviour. British Journal of Psychiatry, 166, 667-675.

Purpose and Objective: The main goal of this  investigation was to determine whether criminality was higher among discharged psychiatric inpatients compared to the general population.

Research Design: Although not specified, it appears that a matched case-control design was used where cases were composed of psychiatric inpatients and controls were composed of community controls matched to the exposed subjects on the basis of sex, age (within 2 years), community size, marital status, and occupational status. Lifetime prevalence of all offenses leading to prison sentences, and all offenses in the past three years leading to fines or prison sentences were compared across the study groups.

Setting: The Psychiatric University Hospital of Berne, Switzerland, which provides primary inpatient care for all residents in the catchment area.

Study Subjects: All psychiatric patients hospitalized in 1987 were included in the study if they were 18-78 years of age. Forty-six subjects could not be matched because their charts contained insufficient information on the matching variables. In total, 1,265 patients were included in the study. The control group was selected from the general population of the catchment area and, because of matching, included 1,265 subjects.

Measures: Presence of mental illness (and case/control status) was defined on the basis of an inpatient psychiatric hospitalization during 1987. However, it is likely that some portion of persons in the control group (selected from the general population) may have been misclassified as they may have had a past history of mental illness or a history of inpatient psychiatric hospitalization. Criminal conviction data were obtained from the Central Criminal Record Department which houses data for the entire country.

Main Findings: In all diagnostic categories, male patients had point estimates for the odds ratio which suggested that they were more likely to have a past history of violent crimes. However, with the exception of alcoholism and drug use disorders, wide confidence intervals (which included the value of 1) suggested that these differences could have occurred by chance. Males with alcoholism and drug use disorders were between three and eight times more likely to have recorded a violent crime. No noteworthy differences among females with respect to violent crimes were reported in any group. However, small cell sizes in some groups resulted in very wide intervals and, therefore, imprecise estimates. Both males and females with alcoholism and drug abuse disorder were more likely to record any kind of crime.

Conclusions: The authors conclude that, in general, there was higher criminality among the mentally disordered in their study. However, persons with schizophrenia were not found to be significantly more violent.

Methodological Critique: The authors  selected controls from the general population and matched on pertinent socio-demographic characteristics. However, it is possible that some members of the comparison cohort could have a history of mental illness and past psychiatric hospitalizations. This would have the effect of suppressing differences between the groups. Similarly, while the authors used matching to control for confounding factors, they failed to use statistical tests appropriate for a matched analysis. As a result, they may have under-estimated the magnitude of differences between the study and comparison groups. These methodological difficulties, combined with the small cell sizes in many of the comparisons, call into question the conclusion of no or marginal differences between persons with “true” mental illnesses (defined by the authors as schizophrenia and affective disorders) compared to those with alcohol and drug abuse problems.

Causality: Given that cases were selected from persons with serious mental illnesses who were hospitalized, it is not possible to derive a general statement of causality from these findings. Also, given the methodological and analytic problems with this work, a lack of statistical precision and misclassification bias cannot be ruled out as plausible explanations for the findings of no or marginal differences reported for some groups.

Newhill, CE., Mulvey, EP. and Lidz, CW. (1995). Characteristics of violence in the community by female patients seen in a psychiatric emergency service. Psychiatric Services, 46(8), 785-789.

Purpose and Objective: An examination of factors associated with violence towards others by female and male patients in the community.

Research Design: Longitudinal follow-up of a case-series.

Setting: Patients were recruited from a psychiatric emergency program in a large, university-based hospital within an urban catchment area.

Study Subjects: A total of 1,871 patients (85%) consented to the study out of a total of 2,293 patients approached during a period of two years. Of those consenting, 862 were selected because of potentiality for violence, or were selected to be control subjects. The report is based on a final sample of 812 patients [317 (39%) females and 495 ( 61%) males].

Measures: Violence was defined as laying hands on another person in a threatening manner, or threatening another person with a weapon. Violence was measured using one or a combination of self-reports of violent incidents, collateral informants, or official records.

Main Findings: During the follow-up period, 369 patients (213 males and 156 females) engaged in violence.

Conclusions: Male and female persons did not differ significantly in frequency or severity of violence, but differed with respect to who the co-combatant was, and  where the incident took place. Gender was not considered to be a strong predictor of violence among psychiatric patients.

Methodological Critique: It is not clear what parameters were used to include only a portion (862) of the total number of consenters. Selection bias may have occurred if those most likely to commit violence were included for study. The lack of a control group of non-psychiatric patients or of a community sample makes it impossible to say whether the prevalence noted in the study sample was higher or lower than would be expected.

Causality: Because these authors did not compare the incidence of violence among their study group with a non-psychiatric comparison group, no statement of causality can be made regarding the relationship of mental illness to violence.

Noble, P. and Rodger, S. (1989). Violence by psychiatric inpatients. British Journal of Psychiatry, 155, 384-390.

Purpose and Objective: The purpose of this study was to examine whether the levels of aggression and assaults among psychiatric inpatients were increasing.

Research Design: While the authors fail to mention study design, the data collection is consistent with a case-control approach. A register of violent incidents was used to identify all the 137 psychiatric inpatients who committed an assault during 1982.

Setting: The data was collected at two locations, the Bethlam Royal and Maudsley Hospitals, London, England. The hospitals are postgraduate teaching hospitals with many special units.

Study Subjects: During 1982, there were 1529 admissions including 568 from the catchment area. Of the patients admitted, 730 were male and 799 were female. The subjects were compared with controls matched for age, sex and psychiatric unit.

Measures: A register of violent incidents was used to obtain information on assaults. This database contained an itemized form that was completed after each assault or threatening incident. The form contained information on the assailant, the victim, the circumstances of the assault, and the nature of any injury. The assaults are rated for severity on a three-point scale. Assaults rated at severity level I were those which did not result in any detectable injury. Assaults rated at severity level II were those which resulted in minor physical injuries. Finally, assaults rated at severity level III were those which resulted in major physical injuries. The case notes of the subjects and controls were rated on 85 clinical and demographic items.

Main Findings: The register identified 137 subjects who had committed 470 assaults. Eighty-one (59%) were rated at severity I, 53 (39%) were rated at severity II, and 3 (2%) were rated at severity III. Violent patients were more likely to have a primary diagnosis of  schizophrenia and were more likely to be hallucinating and delusional, and to have been involuntarily committed. The violent group had significantly more previous admissions than the control group.

Conclusions: The register of violent incidents showed a progressive increase in inpatient violence from 1976 to 1984, followed by a slight decline to 1987. There were a number of characteristics that significantly distinguished violent from non-violent patients. The violent group was best distinguished by their behavioural characteristics during the course of their admissions, and were rated much higher for damage to property, verbal aggression and threatening behaviour.

Methodological Critique: The large number (85) of demographic characteristics compared increased the chances of finding at least one statistical difference just by chance alone. Further, it is difficult to interpret the group differences in light of the fact that a large proportion of violent patients were involuntarily committed, perhaps on the basis of dangerousness to others.

Causality: A causal inference cannot be made on the basis of these findings.

Patel, V. and Hope, R.A. (1992). Aggressive behaviour in elderly psychiatric inpatients. Acta Psychiatrica Scandinavica, 85, 131-135.

Purpose and Objective: This study describes types of aggressive behaviours displayed by hospitalized elderly psychiatric patients.

Research Design: A descriptive cross-sectional survey.

Setting: Warneford and Littlemore Hospitals, Oxford, England.

Study Subjects: Ninety psychogeriatric inpatients on five long-stay treatment units and on one assessment unit. These patients reflect all of the psychogeriatric residents of the two study hospitals.

Measures: The Rating Scale for Aggressive Behaviour in the elderly (RAGE) was used. Data were gathered during the course of studying this instrument’s psychometric properties. Nurses used the RAGE to rate patient’s behaviours during a three day study period. In addition, data on the time of day that aggressive behaviour occurred, the target of this behaviour, and the degree of dependence of the patient on nursing care were collected.

Main Findings: Six percent of subjects inflicted an injury on someone else during the three day observation period. Usually, these were minor (such as scratches), but in one instance, a bruise was caused. Being uncooperative or resisting help occurred most frequently (58.5%), followed by verbal assaultive behaviour such as shouting, yelling, or screaming (46.0%). A significant portion (17.8%) attempted to hit others and 12.3% did push or shove another. There was no relationship between the time of day and aggressive behaviour or the age or sex of the patient. Most behaviours were directed toward ward staff.  Demented patients had a higher level of aggressive behaviour than those with other diagnoses .

Conclusions: Almost half of the sample (45%) were considered to be at least mildly aggressive over the three day period, including 15% of patients who were moderately or severely aggressive.

Methodological Critique: The lack of a comparison group in this study makes it impossible to judge whether the degree of physical assaultiveness in this patient population is higher or lower than psychiatric patients in general, or non-psychiatric controls.

Causality: This study cannot be used to arrive at a causal statement about the relationship between mental illness and violence in general. However, among psychogeriatric patients, results suggest that aggressive behaviour may be associated with a diagnosis of dementia.

Sosowsky, L. (1980). Explaining the increased arrest rate among mental patients: A cautionary note. American Journal of Psychiatry, 137(12), 1602-1605.

See also: Sosowsky, L. (1978). Crime and violence among mental patients reconsidered in view of the new legal relationship between the state and the mentally ill. American Journal of Psychiatry, 135(1), 33-42, for an earlier description of this study.

Purpose and Objective: To compare arrest rates of former mental patients with the general population.

Research Design: Although the author does not name a design, data collection procedures are consistent with a historical cohort study with a variable follow-up of up to 6.5 years.

Setting: San Mateo Country, California, United States of America.

Study Subjects: Study subjects were discharged from Napa State Hospital between 1972 and 1975.

Measures: Crime data for San Mateo Country comprise the comparison population. As this is one of the counties served by the hospital, it does not reflect the general population from which the hospital data were drawn. As such, significant socio-demographic differences between San Mateo Country and the general population served by the Napa State Hospital could confound comparisons.

Main Findings: In keeping with the findings from Steadman, Cocozza, and Melick (1978) (see below), the author stratified the findings according to prior arrest history. Ex-patients were 5.3 times more likely to be arrested for a violent crime during the follow-up period compared to the county comparison group. Ex-patients with one prior arrest were 12.4 times more likely to be arrested for a violent crime and this figure increased to 14.1 for those with two or more previous arrests.

Conclusions: Sosowsky concludes that mental status is causally related to arrest rates.

Methodological Critique: This is the only  report to date showing a higher risk of violent crime among patients with no prior history of arrest. However, the author did not control for demographic differences that may have been apparent between the study cohort and comparison population. Findings could also be accounted for by a lower arrest rate in the comparison population. This would have been less of an issue if the author used the state population instead of a single county with a small population. Because the ex-patients studied do not represent all individuals suffering from mental illness, it is premature to conclude that mental status is “causally” related to arrest rate. The findings have not been appropriately interpreted in light of the potential for selection bias in hospitalized cohorts.

This study generated a number of Letters to the Editor highlighting a number of methodological issues that might have accounted for the higher incidence of arrests in this patient cohort. For example, Diamond [(1981), American Journal of Psychiatry, 138(6), 857] points out that Napa State Hospital patients were a selected group that were more prone to violence because patients with histories of arrests or clinical findings indicative of violence or criminal behaviour tended to be sent to this hospital. Non-violent patients were more likely to be retained for treatment in the local county. In the same issue, Adams (1981) also argues for a selection bias in that hospitalization at a state hospital is based on psychiatrists’ judgements that the patient will be dangerous. The increased association between arrest and hospitalization can, therefore, be interpreted as an indicator of psychiatrists’ good judgement with respect to dangerousness, rather than an association between mental illness and criminality per se.

Causality: A causal inference cannot be made on the basis of these findings.

Steadman, H.J., Cocozza, J.J. and Melick, M.E. (1978). Explaining the increased arrest rate among mental patients: The changing clientele of state hospitals. American Journal of Psychiatry, 135(7), 816-820.

See also: Cocozza, J.J., Melick, M.E. and Steadman, H.J. (1978), Trends in violent crime among ex-mental patients, Criminology, 16(3), 317-334 and Melick, M.E., Steadman, H.J. and Cocozza, J.J. (1979). The medicalization of criminal behaviour among mental patients. Journal of Health and Social Behaviour, 20, 228-237 for similar descriptions.

Purpose and Objective: To compare the arrest rates of two cohorts of patients to the general population. One cohort was chosen to reflect the time period prior to deinstitutionalization, the other, post-deinstitutionalization.

Research Design: The authors do not name their design but the data collection used is consistent with an historical cohort design.

Setting: New York State, United States of America.

Study Subjects: The first study cohort included 1,920 persons discharged between April 1, 1967 and March 31, 1968. The second cohort included 1,938 patients discharged from New York State psychiatric centres between April 1, 1974 and March 31, 1975. Both cohorts were chosen using systematic sampling, every 14th and every 18th discharge, respectively. Subjects were followed, on average, for 19 months after their release from hospital.

Measures: Hospitalization histories were used to obtain socio-demographic and clinical information. Criminal records (both prior and subsequent) were used to describe types of crimes for which persons were arrested. Similar state-wide crime data were used to calculate general population rates. Violent crimes were defined as murder, manslaughter, and assault.

Main Findings: Study subjects were arrested very infrequently following their release from hospital. The proportion of subjects arrested following their release from hospital increased from 6.9% in the 1968 cohort to 9.4% in the 1975 cohort. The proportion arrested for violent crimes increased from 0.0% to 1.7% . Comparisons of these arrest rates to the general New York State population revealed that the 1968 cohort showed a higher arrest rate in every crime category except sexual crime. For violent crimes, the study cohort experienced a rate of 5.58 arrests per 1,000 persons compared to 2.29 in the general population. Similar comparisons made with the 1975 cohort showed a higher rate of arrest in every crime category. For example, for violent crimes, ex-patients were arrested at a rate of 12.03 per 1,000 compared to 3.62 for the general population. Three factors were found to predict arrest among ex-patients: total prior arrests, age, and admitting diagnosis (substance abuse and personality disorder). Patients with no prior arrests had arrest rates that were lower than the general population in every crime category but property offenses, 22.1 per 1,000 arrests compared to 32.5, respectively. Concerning violent crimes, ex-patients with no prior arrests were arrested subsequent to discharge at a rate of 2.2 per 1,000 compared to 3.6 per 1,000 for the general population. On average, patients with one prior arrest were 4.2 times more likely to be arrested compared to the general population and those with more than one previous arrest were 12.7 times more likely to be arrested.

Conclusions: While the arrest rates of ex-patients has risen over time, there is an easily definable sub-group of persons who account for most of the arrests—those with prior arrests. Because greater numbers of persons admitted to state psychiatric facilities have had prior arrests, the overall crime rate among released mental patients has appeared to have increased.

Methodological Critique: The finding that ex-mental patients with prior arrests are at higher risk of criminality and those with no prior history are at lower  risk of criminality compared to the general population has important implications for cohort selection and for statistical controls. Prior arrest should be considered a confounding factor that must be controlled either by design or through appropriate statistical analysis.

Causality: A causal inference cannot be made on the basis of these findings.

Steadman, H.J. and Felson, R.B. (1984). Self-reports of violence: Ex-mental patients, ex-offenders, and the general population. Criminology, 22(3), 321-342.

Purpose and Objective: The main purpose of the study was to compare the self-reported aggression and violence exhibited by ex-mental patients, ex-criminal offenders, and the general population.

Research Design: Cross-sectional design.

Setting: Albany County, New York, United States of America.

Study Subjects: Study subjects included (a) a probability sample of the general population, (b) a non-probability sample of ex-mental patients released from state hospital and residing in the community for at least one year and attending Albany County social clubs for ex-mental patients living in the community, and (c) a non-probability sample of ex-offenders who had been living in the community for at least six months. This latter group included prison parolees and former county jail inmates. The authors point out that neither samples of ex-mental patients or ex-offenders were representative of any well-defined community based population of mentally ill or criminal offenders. Samples were not purified for the study. These investigators estimate that there could be as much as 10% overlap between patient and offender samples such that 10% of ex-offenders were also ex-patients and vice versa. Similarly, some proportion of the general population could be considered to be ex-patients and/or ex-offenders. Overlap was considered to minimize observed effects with the result that the study provided a conservative estimate of the relationship between mental illness and violence.

Measures: Structured self-report questions were designed to elicit measures of aggressive and violent activity of varying severity engaged in within the previous year.

Main Findings: Ex-patients were as likely as the general population to engage in minor forms of aggression such as verbal aggression, slapping or pushing. Ex-patients were found to be more likely to be involved in weapon disputes than the general population, and more likely to have engaged in physical attacks during these incidents. Differences observed between these groups were small and it was clear that ex-patients were not as violent as ex-offenders. Age, sex, and education were found to predict violence with age being the strongest predictor.

Conclusions: The authors conclude that self-report data are consistent with arrest studies  suggesting that differences between the groups cannot be explained by differential treatment by police among arrested samples. Ex-offenders were found to engage in aggressive behaviour at every level of severity and are more likely to cause a physical injury. Ex-patients are more likely than the general population to use weapons and to be involved in hitting disputes. No differences were noted with respect to ex-patients and the general population in the tendency to cause physical injury to the antagonist. Therefore, ex-patients are only slightly more likely to engage in the most serious forms of violence than the general population.

Methodological Critique: Given that both ex-patients and ex-offenders comprised non-representative samples of selected previously institutionalized populations, it is not possible to interpret these findings as supporting an etiological explanation. In addition, the temporal ordering of the onset of mental illness vis-à-vis the expression of violence was not established.

Causality: A causal inference cannot be made on the basis of these findings.

Tardiff, K. and Koenigsberg, H.W. (1985). Assaultive behaviour among psychiatric outpatients. American Journal of Psychiatry, 142(8), 960-963.

Purpose and Objective: The purpose of this study was to assess the rates and patterns of assaultive behaviour among a large group of patients who came to the general outpatient clinics of two private psychiatric hospitals.

Research Design: Although the authors failed to mentioned the type of design, data collection procedures are consistent with a retrospective survey of a case series of patients. Subjects were recruited to the study on the basis of their mental illness.

Setting: The Payne Whitney Clinic and the Westchester Division of the New York Hospital, both large teaching hospitals for Cornell University Medical College, United States of America.

Study Subjects: The study included all patients evaluated by psychiatric residents during a 1.5 year period at the Payne Whitney Clinic and the Westchester Division of the New York Hospital. There were 2,916 patients who came to the outpatient clinics for evaluation during the study period.

Measures: At each hospital, a research assistant reviewed the completed hospital records for all patients evaluated by psychiatric residents in the outpatient settings during the study period. Data were recorded on a structured work sheet that was developed as part of an effort to evaluate the clinical experiences of residents who care for patients at these hospitals. The patients were classified as to the presence or absence of assaultive behaviour toward other persons. Self-injury, damage to objects, or verbal threats were not included in the definition of assault. Diagnoses conformed to DSM-III criteria.

Findings: Approximately 5% of the patients had been physically assaultive toward other persons a few days before the evaluation. Family members accounted for over half of the persons assaulted. Assaultiveness was associated with being male, 20 years of age or younger, and a diagnosis of childhood or adolescent disorders, and mental retardation.

Conclusions: The rate of assault among patients who came for evaluation in outpatient settings was lower than the reported rate of assault among inpatients. Men were more likely than women and younger more likely than older patients to be assaultive.

Methodological Critique: The narrow definition of assault may account for the lower prevalence of violence reported in this study compared to inpatient studies. Conversely, if dangerousness is one criterion for admission, outpatient samples could be expected to exhibit less violence. In addition, generalizations are problematic since the study also included persons with mental retardation.

Causality: A causal inference cannot be made on the basis of these findings.

Volavka J., Mohammad Y., Vitrai J., Connolly M., Stefanovic M. and Ford M. (1995). Characteristics of state hospital patients arrested for offenses committed during hospitalization. Psychiatric Services, 46(8),796-800.

Purpose and Objective: The purpose of this research was to study patients who were arrested for criminal offenses committed while in a psychiatric hospital.

Research Design: Although the authors do not state the type of research design, the data collection procedure is consistent with a case-control study design.

Setting: Manhattan Psychiatric Centre and Rockland Psychiatric Center, two New York State hospitals, United States of America.

Study Subjects: Seventy three inpatients arrested during a thirty month period compared to 1,438 non-arrested inpatients. Cases were 73 patients who were arrested for an incident that occurred while they were inpatients, during the thirty month period. Eleven patients had more than one arrest. Data are provided for the most serious incident. Controls were all patients (N=1,731) hospitalized at both hospitals on March 15, 1992.

Measures: Records of safety departments were searched for information about arrests resulting from inpatient incidents that occurred between January 1, 1991 and June 30, 1993. Demographic data, psychopharmacological treatment at the time of treatment, psychiatric diagnosis, duration of illness, number of previous hospitalizations, and number of prior arrests were abstracted. Using data from court records, the offense charged, the number of court hearings following arrest, the number of patient transfers between hospital and jail, and the court dispositions and  sentences were tracked.

Main Findings: A total of 58 of the 73 arrests resulted from violent incidents involving physical and sexual assaults, robbery, and one murder. Non-violent arrests were related to drug-related offenses, burglary, and arson. The number of arrests increased significantly during the time span of the study, whereas the number of violent incidents appeared to decline. The circumstances described in the records did not generally suggest that violence resulted from psychosis, although this was not studied in detail. Arrestees were more likely to be young, male, black, and have a shorter length of stay. Diagnoses did not differentiate the two groups. Ninety percent had a diagnosis of substance abuse, personality disorders or both.

Conclusions: Arrests of psychiatric inpatients increased during the study period despite declining numbers of inpatients and incidents. Also, the number of violent incidents decreased as the number of arrests increased.

Methodological Critique: This study did not specifically focus on violent crime in relation to mental illness, although a large proportion of the arrests were for violent incidents.

Causality: No statement can be made regarding the causal relationship between mental illness and violence.

Wessely, S.C., Castle, D., Douglas, A.J. and Taylor, P.J. (1994). The criminal careers of incident cases of schizophrenia. Psychological Medicine, 24, 483-502.

Purpose and Objective: To test the hypothesis that compared to other mental disorders, schizophrenia is associated with an increased risk of conviction and an increased rate of convictions.

Research Design: Longitudinal study with a variable follow-up of up to twenty years. Study and comparison subjects were matched on age (within five years), sex, and time of admission.

Setting: Camberwell, London Borough, England.

Study Subjects: Study subjects (N=538) were obtained from a psychiatric case registry and represented new cases of schizophrenia. Comparison subjects (N=538) were drawn from the same register. Those persons whose name appeared directly below that of a selected case subject, and who had any diagnosis other than schizophrenia matched for age (within 5 years) and sex, were selected to be comparison subjects. The authors do not describe a procedure for choosing only new cases among comparison subjects but state that controls differed from cases only in their absence of psychosis.

Measures: Psychiatric diagnosis and criminal convictions were identified from archival records. Schizophrenia was defined according to ICD-9 codes reflecting schizophrenic psychoses. Criminal conviction data were obtained from the Criminal Records Office which  contains 90% of all criminal convictions in the United Kingdom. In addition, a small number of self-reported convictions not found in the official records were added.

Main Findings: Schizophrenia was found to make a small but independent contribution to the risk of acquiring a criminal record but this was overshadowed by the much larger effects of gender, substance abuse, ethnicity, and age of onset of illness. Prior criminality was the strongest predictor of conviction.

Conclusions: While this study demonstrates a small increased risk of criminal conviction among those with schizophrenia compared to other disorders, the major predictors of conviction are factors unrelated to the illness.

Methodological Critique: The authors did not use a comparison group composed of “normal” subjects so findings can only be used to infer whether having a schizophrenic illness increases the risk of subsequent convictions among treated populations of the mentally ill. Both study and comparison groups could have had rates of conviction lower than the general population. The authors state that the only difference between study and comparison groups was the presence of a psychotic illness. However, it is likely that the comparison group included individuals with other psychotic illnesses as the selection procedure did not explicitly exclude these individuals. Because results were based on criminal convictions, this study underestimates the criminality among both study and comparison groups and it is not known whether those with a schizophrenic disorder are more likely to be convicted.

Causality: Because study and comparison subjects were drawn from those receiving treatment and because a normal comparison group was not used, results from this study cannot be used to judge whether persons with mental illness are at increased risk of violence.

Studies based on Samples of Incarcerated Offenders

The following studies have examined samples of incarcerated offenders. Because they focus only on selected populations of incarcerated offenders, they cannot be used to draw etiological inferences concerning the general relationship between mental illness and violence.

Abram, K.M. and Teplin, L.A. (1990). Drug disorder, mental illness, and violence. NIDA Research Monograph, (REA 228).

Purpose and Objective: This study examined whether persons with dual diagnoses (both drug use and mental disorder) commit more violent crimes than persons who abuse drugs but who are not mentally ill. A number of combinations of drug use and psychopathology were also examined for proneness to violent crime.

Research Design: A three year cohort study.

Setting: Cook County Department of Corrections, Chicago, Illinois, United States of America.

Study Subjects: Data were collected between  November 1983 and November 1984 on a random selection of pre-trial male detainees and offenders sentenced for less than one year on misdemeanour charges. Results were presented on 728 subjects.

Measures: Information on drug abuse and mental disorders was collected using the Diagnostic Interview Schedule (DIS). Subsequent arrest and conviction data were obtained from the Chicago Police Department, the Federal Bureau of Investigation, and the Illinois Bureau of Investigation.

Main Findings: The authors constructed statistical models to predict (a) past violent behaviour, and (b) future violent behaviour. With respect to past violent behaviour, none of the drug disorders (marijuana only, opiate only, and polydrug) were found to have a significant effect on past arrests for violent crimes. Violent arrests were associated with age (given greater time at risk), lower education, and presence of antisocial personality disorder. Depressed opiate users were least likely to have violent crimes in their past. With regard to future arrests for violent crimes, the following factors were predictive: previous arrests for violent crimes, days out of jail (the greater the number of days out of jail the greater the opportunity to commit violent crimes), and opiate disorder (diminishing the probability of future arrest for a violent crime). No other factor was significant.

Conclusions: Mental disorders (schizophrenia, depression, alcohol disorder) did not predict arrest for violence, after controlling for variables (such as age or education) that are known to correlate with crime and mental disorder. In contrast, antisocial personality disorder was strongly predictive of past arrests, even after the arrest and conviction items in the DIS were removed as a basis for making this diagnosis. However, antisocial personality disorder was not predictive of future arrests. The prevalence of violent crime among drug disorders, uncomplicated by other disorders, was low, but it should be pointed out that the data were collected prior to the cocaine epidemic. (Cocaine is thought to have a relationship to violent criminality.) Authors conclude that it is the young, poorly educated, antisocial detainee with a violent past who is most likely to be involved in future violent crime.

Methodological Critique: This is a well-structured and well-executed study that employed thorough data collection techniques on a large and representative sample of subjects.

Causality: This study focuses on sub-groups of incarcerated offenders defined in terms of mental disorders and drug/alcohol abuse. While it does not provide a strong basis for drawing conclusions about the causal relationship in unselected populations, results are consistent with the view that there is no association between mental disorders and violence.

Allodi, F. and Montgomery, R. (1975). Mentally abnormal offenders in a Toronto jail. Canadian Journal of Criminology, 17, 277-283.

Purpose and Objective: Using jail medical and general records, this study sought to describe 1) all persons remanded by a court for assessment to the psychiatric unit of a jail, 2) a sub-sample taken from the first sample and who were committed, and 3) all prison records to elicit all those who, over a five year period, had a previous history of psychiatric hospitalization.

Research Design: A retrospective review of records.

Setting: A large jail in Toronto, Ontario, Canada.

Study Subjects: All those inmates (106) sent by a court for assessment to the psychiatric unit of the jail over a period of three months.

Measures: Not a standardized review of files. No specific measure used.

Main Findings: It appears that all persons remanded for an assessment were given a psychiatric diagnosis, however, this is not clearly stated. Persons with schizophrenia made up 25% of the sample, and persons with personality disorder made up 45% (25% of the total being psychopathic) of the sample. Sixty-two percent had a previous psychiatric admission, and 65% had a previous conviction. The total population of the prison for a five year period (1969-1973) having a previous psychiatric admission ranged, from year to year, from 40% to 47%.

Conclusions: A large proportion of the population in this jail had a psychiatric problem on admission, or had had a psychiatric admission prior to incarceration.

Methodological Critique: There are many problems with this study. Foremost, the sample was extremely selected; inmates who were referred for a psychiatric assessment to a jail psychiatric unit. The sample consisted of records of all inmates referred for an assessment, or previously admitted to the jail over specified periods of time. Therefore, the sample may not have been representative of the entire incarcerated population. While this study may support the notion that there is a high prevalence of mental illness among incarcerated populations, it cannot be used to make any statements about a causal relationship between criminality and violence among mentally ill individuals.

Causality: A causal inference cannot be made on the basis of these findings.

Arboleda-Flórez, J. (1994). An epidemiological study of mental illness in a remanded population and the relationship between mental illness and criminality. Ph.D Epidemiology Dissertation. Calgary: The University of Calgary.

Purpose and Objective: To provide estimates of one-month and life-time prevalence, to establish  estimates of comorbid conditions, and to study the relationship between mental illness and crime in an incarcerated population.

Research Design: Cross-sectional survey and secondary data analysis of all pertinent records.

Setting: A remand centre in Calgary, Alberta, Canada.

Study Subjects: Subjects were a representative sex-stratified random sample of 1200 admissions to the Calgary Remand Centre out of a total of 4770 admissions to the Centre during the study period of four and a half consecutive months (July 27 to December 10, 1992). Subjects were examined within the first twenty four hours of admission, prior to court determination. The sample size permitted estimation of mental illness to an accuracy of 1%.

Measures: Structured diagnostic interview schedules were administered by four forensic psychiatrists. Inter-rater reliability was assessed and found to be good. The Hare Psychopathology Checklist was used to augment the Structured Clinical Interview for DSM disorders (SCID). Diagnoses were assigned hierarchically.

Main Findings: Axis I or Axis II diagnoses were made in 728 cases (60.7%). Among females, the most frequent diagnosis was alcohol dependence. Major depression occurred in 26.1% of females. There were no diagnoses of schizophrenia. Among males, the most common diagnosis was alcohol dependence (31.7%). Schizophrenia was found in 1.2%, and major depression in 3.3% of males. Only 5.5% were found to have a personality disorder. The most frequently found comorbid condition was antisocial personality disorder and substance abuse disorder (4.5%). Type of charge (person, property, other) did not differ significantly among those subjects who were mentally ill and those who were not.

Conclusions: There was a high prevalence of mentally ill individuals in this sample, but this is made up mostly of alcohol and drug dependency. Socio-demographic (age, education, ethnicity) and criminological (previous detentions, previous forensic assessments) factors were related to a higher risk of being both mentally ill and criminal.

Methodological Critique: This is a study based on a representative sample of cases admitted to a remand centre, and cases at the very beginning of the justice process. The study provides compelling evidence to support the contention that a significant proportion of incarcerated persons suffer from substance abuse disorders and serious mental illness.

Causality: A causal inference cannot be made on the basis of these findings.

Ashford, J.B. (1989). Offense comparisons between mentally disordered and non-mentally disordered inmates. Canadian Journal of Criminality, January, 35-48.

Purpose and Objective: To compare mentally disordered and non-mentally disordered offenders on type of  offense, history of violence and criminal history in a sample of adjudicated inmates.

Research Design: Case-control on a retrospective review of files.

Setting: Maricopa County Jail system, Arizona, United States of America.

Study Subjects: Two independent samples were taken from a set of retrospective records. One sample was drawn from a list of mentally ill offenders admitted to medical or psychiatric units of the institution (cases, N=294). These inmates were further subdivided into “severely disordered” (those with a chronic diagnosis, N=82) and “mentally disordered” (those with a diagnosis during the current incarceration, N=212). Controls (N=372) came from a sample taken from the classification records of inmates not admitted to the medical or psychiatric units who were considered to be non-mentally disordered.

Measures: No measures were described. Files were reviewed with no mention of how diagnosis were entered.

Main Findings: The prevalence of recent violence among severely disordered was 36%, mentally disordered, 31%, and non-disordered, 22%. For past violence, the proportions were 14%, 10% and 7% respectively.

Conclusions: Both subgroups of mentally disordered inmates differed significantly from the non-mentally disordered group in “history of violence”. Therefore, mentally disordered inmates were considered to be more violent.

Methodological Critique: Strengths of this case-control study include: (1) having been specifically set up to compare mentally disordered to non-mentally disordered offenders on three specific variables, type of current offense, history of violence, and criminal history; and (2) the attempt to make a differentiation between “chronic cases” and “present cases” of mental pathology.

Problems in this study are multiple. This was not a representative sample. For the cases, a random sample was taken of inmates with a psychiatric history. For the controls, a random sample was taken from the files of inmates not classified as mentally ill. Possibilities exist that inmates among the controls could have been mentally ill, but not so classified. Pathology was determined from medical records without any standardization of diagnoses, raters, etc. Differences between chronic and present cases are not explained and overlapping could have easily occurred. Violence was not defined, but classified as recent or past, and its measure depended heavily on self-reports of history of violence contained in the files. Sample sizes were not justified. While findings provide some support, albeit problematic, for a relationship between violence and mental illness in incarcerated offenders, they cannot be used to infer an etiologic relationship outside of the incarcerated setting.

Causality: A causal inference cannot be made  on the basis of these findings.

Barton, W.I. (1982). Drug histories and criminality of inmates of local jails in the United States (1978): Implications for treatment and rehabilitation of the drug abuser in a jail setting. The International Journal of the Addictions, 17(3), 417-444.

Purpose and Objective: The aim of this study was to produce a profile of jail inmates useful for classification models regarding disposition and planning for needs of jails.

Research Design: A cross-sectional survey.

Setting: Thirty seven hundred institutions across the United States of America.

Study Subjects: From a sampling frame of 165,000 inmates a weighted, non- representative sample, of 6,300 was eligible for study. The final sample consisted of 5,300 inmates.

Measures: None specified, but it appears that a special questionnaire was devised to conduct this survey.

Main Findings: About 68% had a history of drug use, and about 40% had used drugs daily. Most inmates who had used drugs were charged with property crime.

Conclusions: A substantial number of inmates in jails had used illicit drugs at some time. Only 24% had been involved in a drug abuse program. This report recommends that jails provide services for this population in conjunction with outside specialized agencies.

Methodological Critique: This was a massive undertaking, yet, the author could have been more explicit about the type of sampling used, whether it was stratified and whether the weights were taken into consideration at the time of analysis. In addition, the analysis is very superficial given the undertaking, the effort, and the resources spent in this survey. While results may be useful for program planning, they do not support a statement of causality between drugs and violence.

Causality: A causal inference cannot be made on the basis of these findings.

Beaudoin, M.N., Hodgins, S. and Lavoie, F. (1993). Homicide, schizophrenia and substance abuse or dependency. Canadian Journal of Psychiatry, 38, 541-546.

Purpose and Objective: This study had three main goals: (1) gather information on the relationship between consumption of alcohol or drugs and assaultive behaviour among three groups of offenders: those with schizophrenia found not guilty of homicide by reason of insanity; those with schizophrenia convicted of homicide; and non-mentally ill offenders convicted of homicide; (2) compare the history of assaultive behaviour between inmates suffering from schizophrenia and the non-mentally disordered inmates; and (3) study the link between the evolution of schizophrenia and assaultive behaviour in homicide offenders with schizophrenia found not guilty by reason of insanity, and offenders with schizophrenics who had been convicted.

Research Design: None described, but this was a cross-sectional study of a convenience sample of persons found not guilty by reason of insanity, and a cross-sectional study from a “target list” of inmates for those with schizophrenia who had been convicted of homicide. Apparently, inmates in this group were culled from a list of “target subjects” identified by the authors. Finally, homicide offenders were identified from different institutions.

Setting: The principal maximum security penitentiary hospital and three penitentiaries at medium and maximum security in Quebec, Canada.

Study Subjects: Fourteen out of 17 patients (83%) found not guilty by reason of insanity after August, 1990, 12 out of 14 offenders with schizophrenia and convicted of homicide (86%), and 15 out of 56 homicide offenders (21%), agreed to participate.

Measures: Structured Clinical Interview for DSM-III-R (SCID) was used for the second group of “target subjects”. The Diagnostic Interview Schedule (DIS) was applied to make a diagnosis of drug and alcohol history. The “Grille d’histoire d’agression physique contre la personne” (GHAP) was used to measure qualitative and quantitative aspects of aggression against the person (defined as an act implying harmful physical contact between two people, either directly, or using an object). Criminal history was determined using the official police records provided by the Royal Canadian Mounted Police. Medical files were used to ascertain diagnosis of not guilty by reason of insanity and to confirm diagnoses of schizophrenia. All subjects had to have an IQ of over 70, which was determined through the Wechsler Adult Intelligence Scale-Revised (WAIS-R).

Main Findings: Significantly, 60% of non-mentally disordered homicide offenders had a history of drug or alcohol abuse or dependency compared to 36% of those found not guilty by reason of insanity. Both groups of convicted offenders were more likely to have committed the offense while under the influence of drugs or alcohol than those found not guilty by reason of insanity. No significant difference was found among the groups for the mean number of aggressive incidents. Persons found not guilty by reason of insanity were found to be more assaultive during an acute phase of their illness compared to those schizophrenic offenders convicted of homicide. Both groups of homicide offenders had the same number of hospitalizations, but those diagnosed with schizophrenia had more hospitalizations after the crime.

Conclusions: Convicted persons with schizophrenia were very similar to those inmates who had no major mental disorder in terms of age at first conviction, consumption of drugs or alcohol, or identification of the victim. They also resembled those found not guilty by reason of insanity in IQ, diagnosis of substance abuse or dependency, number of hospitalizations, age at which schizophrenia first appeared, and choice of victim, and they  differed only with respect to age of first criminal act. Persons with schizophrenia were found to have committed criminal acts earlier than those found not guilty by reason of insanity. The earlier onset of criminality among persons diagnosed with schizophrenia may have resulted in them being labelled as criminals rather than mentally ill.

Methodological Critique: Strengths of this study include as thorough an assessment as was possible for the two mentally ill groups. Unfortunately, the study is affected by methodological errors. The design is cross-sectional, and the sample is clearly highly selected as individuals who are already defined as mentally ill and violent (for the two schizophrenic groups). It is not clear how those found not guilty by reason of insanity were selected or “targeted”. The participation of non-mentally disordered offenders was very low. In addition, no psychometric properties are given on the GHAP. It is not clear why the alcohol and drug abuse or dependency section of the SCID was not used instead of making this diagnosis via the DIS.

Causality: A causal inference cannot be made on the basis of these findings.

Bland, R.C., Newman, S.C., Dyck, R.J. and Orn, H. (1990). Prevalence of psychiatric disorders and suicide attempts in a prison population. Canadian Journal of Psychiatry, 35, 407-413.

Purpose and Objective: To provide prevalence estimates of mental illness in a prison population.

Research Design: Cross-sectional survey.

Setting: A remand centre and a provincial prison (inmates sentenced to two years less one day) in Edmonton, Alberta, Canada.

Study Subjects: A systematic sample of 180 males.

Measures: Diagnostic Interview Schedule (DIS).

Main Findings: Ninety-two percent of the sample had a lifetime prevalence for any disorder, with 87% being accounted for by substance abuse, including alcohol, 57% by antisocial personality disorder, and 23% by affective disorders. The prevalence of schizophrenia was estimated at 2%.

Conclusions: There was a large number of mentally disordered offenders in the prisons surveyed, but most of the pathology is accounted for by substance abuse and personality disorders.

Methodological Critique: The strengths of this study, shared only by a very few other studies in the area, lie in the choice of a representative sample, and in the care taken to make appropriate comparisons to standardized rates for sex and age and to estimates of prevalence of mental illness in the general population of the City of Edmonton. Unfortunately, the study mixed two types of correctional populations, remand and prison, which may have had an effect on the over-representation of  substance abuse cases and antisocial personality disorders. In addition, the study used DIS (based on DSM-III) criteria for diagnosis. These criteria not only over-represent cases of antisocial personality disorder (defined on the bases of criminality) among correctional populations, but also, under-represent other type of mental pathology seen most frequently among this type of population (mental conditions not included in the DIS).

Causality: A causal inference cannot be made on the basis of these findings.

Brownstone, D.Y. and Swaminath, R.S. (1989). Violent behaviour and psychiatric diagnosis in female offenders. Canadian Journal of Psychiatry, 34(3), 190-194.

Purpose and Objective: This study tested the hypotheses that (1) violent crime would be associated with a particular diagnosis, (2) an association would exist between the age at admission and type of crime committed, and age at admission and psychiatric diagnosis, (3) crimes committed by young offenders would be more violent than those committed by older offenders, and (4) psychiatric diagnosis would be related to the first psychiatric admission or the first crime.

Research Design: Retrospective chart review.

Setting: Forensic unit at a mental hospital in Ontario, Canada, containing the only facility for mentally ill female offenders in the province.

Study Subjects: All females (91) referred to the unit for a period of five years, January 1981 to December 1985, whether for psychiatric assessment (47), not guilty by reason of insanity or unfit to stand trial (30), probation orders (5), or transferred from a prison because of mental illness (9).

Measures: A specially constructed form was used for abstraction of data. ICD-9 diagnoses were ascertained by consensus in meetings of multidisciplinary teams.

Main Findings: A previous criminal history was recorded in 41.9% of the sample. The mean age at first conviction was 21.5 years. Violent crimes were committed by 53.8% of the sample. The great majority (72.6%) had a previous history of psychiatric admissions, and the mean age at first psychiatric admission was 24 years. Almost half (42.9%) had a diagnosis of psychosis, most often paranoid psychosis. A personality disorder was found among 35 (38.5%) of the women in the sample.

Conclusions: Offenders less than 30 years of age were more likely to be diagnosed as personality disordered, and those over 30 years of age as psychotic. No difference in age was found for violent or non-violent crimes. Diagnosis was not related to violent crime, and the type of crime was not related to age at first crime, or age at admission.

Methodological Critique: The major strength of this study lies in its being one of the few studies focused solely on women. Because subjects came from a single treatment setting, findings cannot be said to be representative of all female offenders. In addition, the sample mixes women at different points in the criminal justice process. Importantly, in the case of pre-trial remanded cases, the individual, by definition, is still innocent of a crime. Those persons found not guilty by reason of insanity and those found unfit to stand trial may also be innocent. On the other hand, individuals in post-sentenced cases, those on probation, or those in prison have been found guilty. Different selection pressures operate at each of these levels to divert some women out of the process, thereby making the findings of this study very difficult to interpret.

Causality: A causal inference cannot be made on the basis of these findings.

Coid, B., Lewis, S.W. and Reveley, A.M. (1993). A twin study of psychosis and criminality. British Journal of Psychiatry, 162, 87-92.

Purpose and Objective: This study tested four hypotheses: (1) schizophrenic probands have higher rates of criminality than non-schizophrenic twins, (2) schizophrenic twins have higher rates of criminality than those with affective psychosis, (3) schizophrenic twins have a characteristic pattern of offenses compared to non-schizophrenic offenders, and (4) schizophrenia predated onset of criminality.

Research Design: Retrospective follow-up based on chart review of consecutive series of individuals identified as being of twin birth (probands), and their co-twins (twin siblings), to ascertain lifetime criminal and psychiatric histories.

Setting: A major, world-famous, downtown hospital in London, England for probands and for tracing in the community of co-twins.

Study Subjects: The first analysis was conducted on 280 probands, and the second analysis (pair-wise analysis) was conducted on 220 pairs of twins. The total sample was reported to consist of 490 subjects. [Numbers do not add up due to presence of double probands (both twins with criminal records)].

Measures: Zygosity was established though serological matching or by a recognized physical resemblance questionnaire. Subjects were examined with the Schedule for Affective Disorders and Schizophrenia (SADS-L), and lifetime diagnosis assigned using DSM criteria and the Research Diagnostic Criteria.

Main Findings: Among the probands, 57.5% were diagnosed as bipolar, 35% as having schizophrenia, 2.5% as having schizophreniform, 2.5% as being paranoid, and 2.5% as having organic psychosis. In contrast, 50.4% of co-twins did not have a mental disorder. Approximately 33% had a bipolar disorder, and 9.7% had a schizophrenic or schizophreniform illness. Of the total sample of 490 individuals, 16.9% had at least one criminal conviction, and  of the probands, 21% had a criminal record. Significantly more probands had criminal convictions (25.7%) than did their respective co-twins (14%).

Conclusions: There was no effect of twin zygosity on the presence of criminality. Among ill subjects, diagnosis had a significant association with criminality. More men were criminals and schizophrenic, and more of those who were schizophrenic were criminals. Schizophrenic probands had more criminal records than bipolar probands, and were more violent. Illness preceded criminality in 57.6% of the cases. It was suggested that criminal convictions are increasing among the psychotic population.

Methodological Critique: This may be one of the few studies comparing mental illness and criminality among twins. The authors did try to find twin birth history among the probands, to find co-twins, to ascertain zygosity, and to ascertain diagnosis among the co-twins. The major flaws of the study lie in the long follow-up and the difficulties of standardizing diagnostic systems throughout the long period (40 years), and the over-representation of males in the schizophrenic group. The lack of criminal history is also problematic in the comparison between the two groups. The authors conclude that criminal convictions are increasing among the psychotic population without an appropriate comparison group.

Causality: A causal inference cannot be made on the basis of these findings.

Côté, G. and Hodgins, S. (1992). The prevalence of major mental disorders among homicide offenders. International Journal of Law and Psychiatry, 15, 89-99.

Purpose and Objective: To estimate life-prevalence of major mental disorders among penitentiary inmates convicted of homicide.

Research Design: Cross-sectional survey of a representative sample, and comparison of homicide offenders to non-homicide offenders.

Setting: Penitentiaries in Quebec, Canada.

Study Subjects: A representative sample of 650 inmates of whom 460 (70.8%) were interviewed and among whom 87 had been convicted of homicide.

Measures: Diagnostic Interview Schedule, DIS version III-A. Sixty-nine subjects were re-interviewed five weeks after the first interview by a different interviewer, and kappa .78 was obtained indicating good inter-rater reliability.

Main Findings: A total of 109 subjects suffered from a major mental disorder. On applying DSM-III exclusion criteria to allow only one major diagnosis per subject, more homicide subjects (35%) than non-homicide subjects (21%) suffered from a major mental disorder, usually schizophrenia. When DSM-III exclusion criteria were relaxed, recurrent major depression was more characteristic of homicide offenders. In 82% of cases with schizophrenia and 83% of those with major depression, the mental disorder  preceded the homicide.

Conclusions: The lifetime prevalence of mental disorder is higher among male offenders convicted of homicide than among other type of offenders. In the majority of cases, the mental disorder preceded the offense.

Methodological Critique: The main strength of this study pertains to the use of a representative sample. Unfortunately, however, subjects were highly selected from individuals already found guilty of an offense so do not reflect more general patterns of violence. The use of DSM-III criteria and of the DIS presents problems due to tautological definitions of violence and mental illness.  Although temporal ordering of factors is established, results are not generalizable to all violent individuals.

Causality: A causal inference cannot be made on the basis of these findings.

Feder, L. (1991). A comparison of the community adjustment of mentally ill offenders with those from the general prison population. Law and Human Behaviour, 15(5), 477-493.

Purpose and Objective: The purpose of this study was to compare the post-prison adjustment of mentally ill offenders and a comparable group of non-mentally ill offenders, and to examine the extent to which differences could be accounted for by mental illness.

Research Design: A prospective longitudinal design was used with an eighteen month post-prison follow-up.

Setting: New York, United States of America.

Study Subjects: Study subjects were 400 non-mentally ill offenders and 147 mentally ill offenders discharged from prison between July 30, 1982 and September 1, 1983.

Measures: Mentally ill offenders were defined as persons requiring psychiatric hospitalization during their incarceration. No information is provided on the diagnostic mix. Non-mentally ill offenders were those who did not require hospitalization. As the author points out, some comparison subjects could have been suffering from mental illnesses that either did not require hospitalization, or were not obvious to prison staff.

Main Findings: Mentally ill offenders were more likely than non-mentally ill offenders to have been arrested for a violent crime. Also, some differences existed between the groups with respect to other demographic and history variables.

During follow-up, 64% of mentally ill offenders and 60% of non-mentally ill offenders were re-arrested at least once. With respect to violent crimes, 19% of mentally ill offenders and 15% of non-mentally ill offenders were re-arrested. These differences were not statistically significant. Mentally ill offenders were re-arrested significantly less frequently for drug offenses.

Differences were noted between mentally ill offenders and non-mentally ill offenders with respect to the way in which arrests for non-violent crimes were handled: mentally ill offenders received a sentence involving prison time less frequently than did non-mentally ill offenders, and were channelled more often into the mental health system than their non-mentally ill counterparts. No differences were noted with respect to violent crimes, indicating that discretion among criminal justice personnel decreases in cases of serious offenses. When statistical techniques were used to control for groups differences in criminal history, the only significant factors distinguishing the groups in subsequent arrests were age and prior arrests. Psychiatric status was not significant.

Conclusions: With the exception of drug-related offenses which were lower among mentally ill offenders, psychiatric status did not explain variations in post-release arrests for violent or other types of crime. The major explanatory factors were younger age and prior arrests. However, together, these only accounted for 8% of the total variation indicating that there are many factors, other than the ones studies, that account for post-prison adjustment.

Methodological Critique: The problem with (1) classifying mentally ill offenders based on psychiatric hospitalization and (2) the resulting possibility that some of the comparison group may have been suffering from mental illness, may explain the lack of difference noted in subsequent community adjustment. This would be particularly problematic if a high proportion of comparison subjects were suffering from substance abuse disorders that would be unlikely to prompt a psychiatric admission, but which are shown in other studies to be associated with higher post-release criminality.

Causality: Because this study uses selected samples from institutionalized offender populations, results cannot be used to infer causality.

Gingell, C.R. (1991). The criminalization of the mentally ill: An examination of the hypothesis. Doctoral Dissertation. Burnaby, British Columbia: Simon Fraser University.

Purpose and Objective: To establish estimates of prevalence and to examine the value of the criminalization hypothesis.

Research Design: Cross-sectional design.

Setting: A local jail in Vancouver, British Columbia, Canada.

Study Subjects: A non-representative sample of 317 consecutive admissions from whom a “selected group” identified as having a “high probability of mental illness” was chosen for further study. A second group consisted of 107 inmates selected through a stratified random sample from the general prison population.

Measures: Brief Psychiatric Rating Scale and Diagnostic Interview Schedule (DIS) were used for only a  “selected group of inmates”.

Main Findings: High rates of prevalence of schizophrenia in both the first and second groups, with rates of 8% and 13% respectively.

Conclusions: Support was found for the criminalization hypothesis. A large number of mentally ill individuals, specially those suffering from major mental conditions, end up in prisons.

Methodological Critique: The use of DIS is considered inappropriate for this type of population given a circularity of symptoms and criminal offenses, some of the symptoms implying acts of violence. Futhermore, this study has methodological problems regarding the sampling strategy and the peculiar selection of subjects selected for the first group. This may have resulted in selection bias as well as subjective bias on the part of the researcher.

Causality: A causal inference cannot be made on the basis of these findings.

Grunberg, F., Klinger, B.I. and Grumet, B. (1977). Homicide and deinstitutionalization of the mentally ill. American Journal of Psychiatry, 134(6), 685-687.

Purpose and Objective: To examine if there has been a disproportionate increase of crimes committed by the mentally ill, and whether this is due to the shift from institutional to community-based care.

Research Design: Retrospective review of files.

Setting: Small county in New York State, United States of America.

Study Subjects: All 48 cases of homicides where offenders were either convicted or found not guilty by reason of insanity were identified from the county prosecutor files for the period January 1, 1963-December 31, 1975.

Measures: Cases were divided into four groups: guilty with or without previous psychiatric hospitalizations, and not guilty by reason of insanity with or without previous psychiatric hospitalizations. Data were collected for two periods: before 1969, the year the community psychiatric centre was established in the county; and after 1969.

Main Findings: The proportion of those found guilty and not previously mentally ill remained the same for the two periods, whereas those found not guilty by reason of insanity with previous hospitalizations increased six-fold.

Conclusions: Mental illness may be related to violence (homicide) and this may be related to policies of deinstitutionalization.

Methodological Critique: This is an interesting study because of the way in which the investigators operationalized their concepts. However, the small sample size of the study is problematic. In addition, mental illness was defined in very broad terms (not guilty by reason of insanity, or previous hospitalizations). Conversely, criminality was defined solely in terms of  homicide. Other factors that could have been related to the homicides were not considered.

Causality: A causal inference cannot be made on the basis of these findings.

Guze, S.B., Goodwin, D.W. and Crane, J.B. (1969). Criminality and psychiatric disorders. Archives of General Psychiatry, 20, 583-591.

Purpose and Objective: To determine the prevalence of psychiatric disorders and to measure the associations between mental illness and criminality.

Research Design: Longitudinal follow-up design.

Setting: Subjects were followed up over an eight- to nine-year period in various communities in the United States of America.

Study Subjects: The subjects were 223 convicted felons on parole, 94% of whom were located for follow-up.

Measures: Data were collected using structured diagnostic interviews with the study subjects and through interviews with their families. Criminality was defined as a felony conviction.

Main Findings: Sociopathy, drug dependency, and alcoholism were most frequently associated with criminality. Schizophrenia, affective disorders, and organic brain syndromes were not over-represented compared to the general population.

Conclusions: There is an increased risk of criminality for those patients suffering from alcohol dependency, sociopathy, or drug dependency.

Methodological Critique: Despite the massive efforts of this study, a number of major deficiencies were present including the diagnostic labels used, the type of instruments used, and the lack of control for other factors that could have been related to criminality. Subjects were selected for the sample on the basis of criminal activity and, therefore, positive associations may be more likely. Temporality between the diagnosis of mental illness and the crime was not clearly established with the result that the mental illness may have occurred subsequent to the criminality.

Causality: A causal inference cannot be made on the basis of these findings.

Hodgins, S. and Côté, G. (1993). The criminality of mentally disordered offenders. Criminal Justice and Behaviour, 20(2), 115-129.

Purpose and Objective: To address two hypotheses: (1) that mentally disordered inmates, compared to non-mentally disordered inmates, would have a history of more convictions and more convictions for violent offenses; and (2) among mentally disordered inmates, those with co-occurring antisocial personality disorder would have more total convictions and more convictions for violent offenses than those non-mentally disordered.

Research Design: The authors do not specify the design used, but data collection is consistent with a cross-sectional sample from which respondents were divided into two groups for comparison: mentally disordered inmates and non-mentally disordered.

Setting: A major Canadian federal penitentiary in Quebec (carceral institution holding inmates sentenced to serve over two years of time).

Study Subjects: A representative sample (461 subjects) taken from all male inmates (2,972) being held at the penitentiary on the date of survey (April 13, 1988). A total of 107 were mentally disordered and 349 were not.

Measures: Inmates were administered the Diagnostic Interview Schedule Version III-A. A sub-sample was re-examined by a different interviewer five weeks after with good interrater agreement (kappa = .78).

Main Findings: Mentally disordered inmates were not found to have a history of more convictions and more violent convictions than non-mentally disordered inmates. Among those with a mental disorder, those with a comorbid condition (a major mental disorder plus antisocial personality disorder) had more convictions, but no difference was found with respect to more violent convictions.

Methodological Critique: Findings from this study support the notion that mentally disordered offenders are not processed differently in the criminal justice system compared to non-mentally disordered offenders. However, it is not clear whether this relationship holds among non-institutionalized samples.

Causality: A causal inference cannot be made on the basis of these findings.

Hodgins, S. and Hébert, J. (1984). Une étude de rélance auprès de malades mentaux ayant commis des actes criminelles. Revue canadienne de psychiatrie, 29(8), 669-675.

Purpose and Objective: To follow persons found unfit or not guilty by reason of insanity to compare those placed in a maximum security psychiatric hospital with those placed in other mental hospitals or psychiatric units in general hospitals.

Research Design: A historical follow-up study with a follow-up period of seven to nine years.

Setting: A maximum security psychiatric hospital, six psychiatric hospitals, and thirteen general hospital psychiatric units in the Province of Quebec, Canada.

Study Subjects: Two hundred and seventy five subjects: (a) all those found unfit; and (b) all those found not guilty by reason of insanity over a period of three years (1973 to 1975).

Measures: Data were obtained from clinical records, Royal Canadian Mounted Police (RCMP) files, or the Commission d’Examen du Quebec.

Main Findings: Social disadvantage was a  common denominator among the groups. With the exception of the location where the crime was committed, the groups did not differ in important respects (e.g. destination after hospitalization, duration of outpatient treatment, and occupation). Thirty percent had been treated at the maximum security hospital. The majority of those who were violent, usually males, had been admitted to the maximum security hospital.

Conclusions: The majority of those found not guilty by reason of insanity suffered from schizophrenia. Further crimes during the follow-up period were committed by 27.5%: 25.9% among those from the maximum security hospital and 33.9% from the other institutions. Overall, community clinical follow-up and social opportunities for these patients were deficient.

Methodological Critique: This study provides excellent data describing patients’ re-entry into the community. However, the study is marred by the usual problems of retrospective follow-ups including the need to rely on records assembled by many coders, diagnoses given by many unknown clinicians, and information provided by many different people. It is not clear what a priori theoretical rationale governed the researchers’ choice of the two study groups. Also, the objectives of the study appear very broad and unfocused.

Causality: Because this project was designed to examine how these two groups of mental patients fared once released, not to test any associations, no statement can be made about any putative relationship between mental illness and violence.

Lamb, H.R. and Grant, R.W. (1982). The mentally ill in an urban county jail. Archives of General Psychiatry, 39, 17-22.

Purpose and Objective: To review patterns of mental illness, and type of criminal offense to test the “criminalization” theory.

Research Design: Cross-sectional design.

Setting: A county jail for men in a large metropolitan area in the United States of America.

Study Subjects: A random sample (102) taken from all those referred for a psychiatric evaluation to the forensic unit of the jail.

Measures: None mentioned, but subjects were examined by the authors using DSM-III criteria.

Main Findings: Ninety percent had prior psychiatric hospitalizations, and 92% had prior arrests. More than half were facing a felony charge of which 39% were facing a crime of violence. A large proportion (78%) had histories of serious physical violence. Psychiatric hospitalizations were recommended in 76% of the cases.

Conclusions: This population was characterized by extensive experience with the justice and mental health systems, severe acute and chronic mental illness, and poor functioning.

Methodological Critique: It is not clear how  the results of this study based on a highly selected sample of persons referred for forensic assessment could be used to test the criminalization thesis.

Causality: A causal inference cannot be made on the basis of these findings.

Lamb, H.R., Weinberger, L.E. and Gross, B.H. (1988). Court-mandated community outpatient treatment for persons found not guilty by reason of insanity: A five year follow-up. American Journal of Psychiatry, 145(4), 450-456.

Purpose and Objective: To study readjustment into the community of persons found not guilty by reason of insanity and referred to a community outpatient program.

Research Design: Prospective, longitudinal, follow-up for five years up to December 31, 1985.

Setting: Conditional Release Program of the Department of Health of Los Angeles, California, United States of America.

Study Subjects: Seventy-nine subjects found not guilty by reason of insanity from July 1, 1979 to December 31, 1980 and who were referred to community supervision and treatment.

Measures: Readjustment was measured in terms of re-arrest, hospitalization, and revocation rates.

Main Findings: During the follow-up period, 32% were rearrested (72% on crimes of violence), 47% were hospitalized, and 48% of those on conditional release were revoked.

Conclusions: This population needs social controls and long-term treatment while in the community.

Methodological Critique: Although the authors were careful with the general parameters of the follow-up study, the sample was obviously highly selected for both serious violent crime and mental illness. Although a large proportion was re-arrested for crimes of violence, the authors do not provide other reasons for re-arrest or revocation, so it is not known what proportion of these cases were re-arrested or revocated for minor crimes.

Causality: Due to the selection biases and the lack of control for potential confounding factors, this study cannot be used to make a statement on the matter of causality between mental illness and criminality.

Larkin, E., Murtagh, S. and Jones, S. (1988). A preliminary study of violent incidents in a Special Hospital (Rampton). British Journal of Psychiatry, 153, 226-231.

Purpose and Objective: The purpose of the study was: (1) to study the nature, type, location, times, severity, and object of all violent incidents in the wards of a maximum security unit in the United Kingdom; and (2) to compare findings with data from similar studies in general hospitals.

Research Design: A six-month prospective study of all violent incidents.

Setting: A maximum security unit  specifically set up by law for patients “subject to detention who require treatment under conditions of special security on account of their dangerous, violent or criminal propensities”.

Study Subjects: All violent incidents (N=1144) that occurred during the six months of the study (rather than violent individuals) were the main focus of study.

Measures: Data were collected using a special questionnaire designed for this purpose. Violence was defined as causing injury or damaging property.

Main Findings: Eleven hundred and forty four incidents reported (reporting rate of 60% in female wards and 80% in male rooms). Females comprised 25% of the total population, but represented 75% of the total number of incidents. Nursing staff were three times more likely to be the target of assaults.

Conclusions: As expected, violent incidents occurred more frequently in the Special Hospital, were more serious in nature, and resulted in greater injury.

Methodological Critique: This is a good prospective study on the issue of violence in inpatient units, in this case a secure unit. By definition, though, these units take the most seriously and violent of mental patients, and those who had already been adjudicated as criminal. Hence, the sample is highly selected with individuals who are both criminal and mentally ill. The study, although prospective, does not make any statement in relation to diagnosis, or to correlation between illness and type of violence.

Causality: A causal inference cannot be made on the basis of these findings.

Lindqvist, P. (1986). Criminal homicide in Northern Sweden 1970-1981: Alcohol intoxication, alcohol abuse and mental illness. International Journal of Law and Psychiatry, 8, 19-37.

Purpose and Objective: To review cases of homicide and determine the frequency of alcohol intoxication and mental illness among victimizers, and to compare alcohol-related homicides to sober homicides.

Research Design: Review of records.

Setting: A small, sparsely populated area of Sweden.

Study Subjects: All homicide offenders in the area during the study period (64 with 71 victims), January 1, 1970 to December 31, 1980.

Measures: Data were collected from files.

Main Findings: The homicide rate was estimated to be 0.7%. Mutual intoxication (both victim and victimizer) was found in 44% of the cases. The majority of victims were related to the offenders. Sixty-three percent of offenders had had previous psychiatric care. Alcohol abuse was prevalent (30%) among the sample; an additional 27% were mentally ill. Nineteen offenders were sober with no previous criminal record.

Conclusions: Alcohol is an important factor in homicides.

Methodological Critique: The major problem with this study is the method of ascertainment of alcohol use at the time of the offense. This was sometimes determined by information from third parties rather than by alcoholemia (level of alcohol in the blood). No information is given about the quality of the information contained in the records so it is unclear to what extent cases of alcoholism or mental illness could have been under-reported. In addition, it is not clear how soon offenders were arrested after the offense, thus it is impossible to ascertain the association between alcohol consumption and the offense.

Causality: A causal inference cannot be made on the basis of these findings.

Martell, D.A. and Dietz, P.E. (1992). Mentally disordered offenders who push or attempt to push victims onto the subway tracks in New York City. Archives of General Psychiatry, 49, 472-475.

Purpose and Objective: This study was undertaken in order to shed light on the characteristics of persons who push victims onto subway tracks.

Research Design: A descriptive review of a case series of files.

Setting: New York State Office of Mental Health, New York City, United States of America.

Study Subjects: Data were available on twenty of the 26 subjects.

Measures: Data were abstracted from files using a structured protocol.

Main Findings: All but one (19, 95%) of the subjects were mentally ill at the time of the offense and had a history of psychiatric admission (71% for schizophrenia). Sixty-five percent were homeless.

Conclusions: Homelessness and mental illness appear to be important factors in this type of crime.

Methodological Critique: This is an interesting study but suffers from a very small and selected study group and the lack of a comparison group.

Causality: A causal inference cannot be made on the basis of these findings.

McKnight, C.K., Mohr, J.W., Quinsey, R.E., and Erochko, J. (1966). Mental illness and homicide. Canadian Psychiatric Association Journal, 11(3), 91-98.

Purpose and Objective: To study demographic, criminological, and clinical characteristics of homicide offenders.

Research Design: A retrospective review of records.

Setting: A maximum security hospital in the Province of Ontario, Canada.

Study Subjects: One hundred cases of homicide directly referred from the courts over a period  spanning 30 years.

Measures: Information was obtained from the clinical records.

Main Findings: The majority of subjects (81%) were charged with murder as opposed to manslaughter. Twenty-seven percent were not guilty by reason of insanity. Fifty-seven percent were diagnosed as suffering from schizophrenia and of these, 40% from paranoid schizophrenia. Peak ages at the time of offense were from 30 to 35 years.

Conclusions: The authors conclude that the most serious crime of murder seems to be most commonly committed by schizophrenic patients.

Methodological Critique: There is no special strength to this study. It consisted of a review of records spanning a long period of time, among a population which by definition has been adjudicated criminal and mentally ill, at the most severe level for both. The sample was highly selected, no standardization of instruments was used, and no comment was provied on the quality of data, which is usually very poor in old records. The authors’ conclusions go well beyond the data provided by this very descriptive study.

Causality: A causal inference cannot be made on the basis of these findings.

McMain, S., Webster, C.D. and Menzies, R.J. (1989). The post-assessment careers of mentally disordered offenders. International Journal of Law and Psychiatry, 12, 189-201.

Purpose and Objective: This study was a preliminary attempt to monitor the institutional careers and post-discharge functioning of mentally disordered offenders over a long period of time.

Research Design: Prospective follow-up of a cohort formed by individuals discharged after a forensic assessment.

Setting: Community follow-up of patients discharged from hospitals in Toronto, Ontario, Canada.

Study Subjects: Two hundred patients discharged in 1979 from a forensic service in Toronto were followed for six years.

Measures: Information was gathered from mental hospitals and correctional records.

Main Findings: Ninety-two percent of the cohort incurred a period of incarceration or hospitalization during the follow-up period, and a majority experienced repetitive cycles of institutionalization with decreasing frequency as the follow-up period progressed. Only 8% were able to avoid hospitalization or reincarceration.

Conclusions: It is possible that forensic inpatient assessment may be related to the repetitive cycles of further institutionalization in the years following discharge.

Methodological Critique: This is a preliminary report that deals with the adjustment of forensically assessed mental patients in the community. Given the absence of a control group of persons who did not  undergo a forensic assessment, the conclusions made by the authors go beyond the scope of the data provided.

Causality: A causal inference cannot be made on the basis of these findings.

Menzies, R.J. and Webster, C.D.(1987). Where they go and what they do: The longitudinal careers of forensic patients in the medicolegal complex. Canadian Journal of Criminology, 29, 275-293.

Purpose and Objective: To map the post-assessment careers of forensically assessed mental patients.

Research Design: Longitudinal, prospective cohort study with a two-year follow-up period.

Setting: Community, mental hospitals around Metropolitan Toronto in Canada.

Study Subjects: A cohort of 571 subjects discharged from a forensic assessment unit in Toronto in 1978.

Measures: Data were abstracted from records from hospitals and correctional agencies.

Main Findings: One quarter of the cohort were repetitively reincarcerated or rehospitalized, 36% were reincarcerated but not rehospitalized, and 25% were rehospitalized but not reincarcerated. Repetitive forensic assessments were experienced by 24.4% of the sample. One-third of the cohort showed assaultive behaviour during the follow-up period, over half of these while in the community.

Conclusions: There is a system problem in forensic remands that may be related to the cyclicity of remands and reinstitutionalizations.

Methodological Critique: A strength of this study is the prospective follow-up of this group of patients. However, a control group was not included, and, therefore, the authors cannot offer evidence to support the claim that there may be a system problem fostering cyclicity of remands and reinstutionalizations. No consideration was given to the alternate hypothesis that reinstutionaliztions were due to recurring mental problems.

Causality: A causal inference cannot be made on the basis of these findings.

Nestor, P.G. (1992). Neuropsychological and clinical correlates of murder and other forms of extreme violence in a forensic psychiatric population. The Journal of Nervous and Mental Disease, 180(7), 418-423.

Purpose and Objective: To examine the relationship between neuropsychological impairment and severe violence.

Research Design: Retrospective review of records.

Setting: A maximum security psychiatric hospital. Location not specified.

Study Subjects: Forty patients referred for neuropsychological evaluation between the years 1987 and  1989. These subjects were divided into two groups: the young group (N=22) below age 25 (mean age 19.3 years), and the old group (N=18) above 25 (mean age 41.4 years).

Measures: DSM-III-R diagnosis had been recorded on all the subjects, and subjects had been administered the Wechsler Adult Intelligence Scale-Revised (WAIS-R) as a measure of various aspects of intelligence, the Wide Range Achievement Tests for oral reading, written spelling and arithmetic, and the Trail Making Test (Part B). Police records were also reviewed.

Main Findings: The two groups did not differ significantly in history of drug use. The older group had more diagnoses of psychosis and more hospitalizations. The young group had more learning disabilities and a larger history of court involvement.

Conclusions: Neuropsychological and clinical profiles differed between the two groups, but both groups had a history of substance abuse. Older offenders were more likely to have acted alone and to have victimized a relative.

Methodological Critique: This was a review of records whose quality of diagnosis is not described. In addition, the neuropsychological examination appears superficial. The sample is obviously highly selected, and confounding factors such as socioeconomic status, were not considered.

Causality: A causal inference cannot be made on the basis of these findings.

Nicol, A.R., Gunn, J.C., Gristwood, J., Foggitt, R.H. and Watson, J.P. (1973). The relationship of alcoholism to violent behaviour resulting in long-term imprisonment. British Journal of Psychiatry 123, 47-51.

Purpose and Objective: To explore the relationship between severe violent behaviour and alcoholism.

Research Design: Cross-sectional, correlational study.

Setting: A prison for long-term offenders in the southeast of the United Kingdom.

Study Subjects: Study subjects comprised 90 (out of a total of 98) consecutive referrals of male recidivists who had been given a long-term sentence by the courts. These subjects were divided into two groups for analysis, violent and non-violent, and into two age groups, over and below 30 years of age.

Measures: Interviews, reports contained in files, neuropsychological testing (Raven’s Progressive Matrices), and a special grid to measure responses to particular social situations were used.

Main Findings: Offenders with a diagnosis of alcoholism were significantly more likely to be violent regardless of age, but more young men, whether or not they were alcoholic, were more violent. Violent men were found to be less intelligent. No significant difference was found between the violent and the non-violent men on psychiatric  characteristics, marital history, or social class.

Conclusions: The most seriously violent criminals in this sample were also those having the most severe drinking problem.

Methodological Critique: This is a cross-sectional, correlational study based on a highly selected sample. The subjects were both alcoholics and criminals at the time of the evaluation. Potentially confounding variables were not controlled. No mention was made about how psychiatric diagnoses were obtained, and no details were given about the qualities of one important instrument used, namely, the social grid. It appears that this instrument did not allow the subjects to choose socially appropriate responses.

Causality: A causal inference cannot be made on the basis of these findings.

Pasewark, R.A., Bieber, S., Bosten, K.J., Kiser, M. and Steadman, H.J. (1982). Criminal recidivism among insanity acquittees. International Journal of Law and Psychiatry, 5, 365-374.

Purpose and Objective: To examine the post-hospitalization arrests of defendants adjudicated not guilty by reason of insanity.

Research Design: Prospective follow-up study with a maximum ten year follow-up.

Setting: Community follow-up in the State of New York, United States of America.

Study Subjects: One hundred and forty eight individuals found not guilty by reason of insanity in the State of New York from 1971 to 1976. For comparison purposes the group was divided into two: those that were “released” (N=133) and those that “escaped” (N=15).

Measures: The report does not indicate how or where data were obtained. Presumably information came from mental hospitals and correctional agencies.

Main Findings: Thirty percent of males and 36% of females in the released group experienced rehospitalizations, and 32% of males and 14% of females were rearrested. Among the escapees, only 7% were rehospitalized and 20% rearrested.

Conclusions: Subsequent to hospital release, a significant proportion of persons found not guilty by reason of insanity engage in criminal behaviours. If this behaviour was due to an established pattern of antisocial behaviour, then the psychiatric treatment received does not seem to have been effective.

Methodological Critique: This is one of the few community follow-up reports of not guilty by reason of insanity acquitees. Because the comparison group was a subset of acquittees, no inferences can be made concerning whether their adjustment might be better or worse than non-acquittees.

Causality: A causal inference cannot be made on the basis of these findings.

Phillips, M.R., Wolf, A.S. and Coons, D.J.  (1988). Psychiatry and the criminal justice system: Testing the myths. American Journal of Psychiatry, 145(5), 605-610.

Purpose and Objective: To test popular beliefs about mentally ill offenders though a description of the actual practice of forensic psychiatry.

Research Design: Data linkage from police records, court reports, and clinical files.

Setting: Alaska Psychiatric Institute, mental health clinics and legal/correctional agencies.

Study Subjects: Three different units of analysis were used: the individual; the criminal case; and the referral. There were 1,816 individuals who had been referred from the criminal justice system between 1977 and 1981. These individuals had a range of 1 to 12 referred arrests.

Measures: Data were abstracted in a review of records.

Main Findings: Violent crimes against persons accounted for 12% of all arrests. Twenty-eight percent of patients with schizophrenia were arrested for violent crimes compared to 51% of patients with alcoholism. Only 0.2 to 2.0% of all schizophrenic persons in the community were arrested for violent crime per year accounting for only 1.1% to 2.3% of all arrests for violent crimes.

Conclusions: Evaluation of the actual operation of forensic laws and programs needs to be more comprehensive and more systematic.

Methodological Critique: This is an ambitious project which, unfortunately, relies heavily on data whose quality cannot be assessed. Despite the technological accomplishment of the record linkage, no comparison group is included for study.

Causality: A causal inference cannot be made on the basis of these findings.

Raine, A. (1993). Features of borderline personality and violence. Journal of Clinical Psychology, 49(2), 278-281.

Purpose and Objective: To test hypothesis that borderline personality characterizes extreme violence.

Research Design: Not specified but appears to be a case series design.

Setting: A top-security prison in England.

Study Subjects: Thirty-seven volunteer prisoners were divided into three groups: murderers; violent offenders; and non-violent offenders.

Measures: DSM-III diagnosis of borderline and schizotypal personality and a semi-structured interview, the Diagnostic Interview for Borderlines, were used.

Main Findings: A linear relationship exists between borderline personality scores and extreme violence across the three groups, that is, the higher the borderline scores, the higher the severity of violence.

Conclusions: Borderline personality may predispose towards extreme forms of violence.

Methodological Critique: Study strengths include a good attempt to control for several factors such as age, social class, IQ, and previous custodial sentences. This is a very small and selected series of volunteer prisoners who have been found guilty of severe crimes. Despite a disclaimer by the author, borderline diagnoses are related to an “intense anger” criterion, and hence there was potential for confounding. It is not clear whether there is an overlap between violent offenders and murderers.

Causality: A causal inference cannot be made on the basis of these findings.

Rice, M.E. and Harris, G.T. (1995). Psychopathy, schizophrenia, alcohol abuse, and violent recidivism. International Journal of Law and Psychiatry, 18(3), 333-342.

Purpose and Objective: To examine the relationships among schizophrenia, psychopathy, alcohol abuse, and violent recidivism in a group of serious male offenders.

Research Design: Data from two matched cohort studies were combined to address the study question. In each study two groups were followed: mentally disordered offenders from a maximum security psychiatric institution; and convicted offenders, matched for index offense, age at index offense, and criminal history. Study subjects were followed up until April, 1988 for an average of 97.1 months.

Setting: Maximum-security psychiatric institution in Penetanguishene, Ontario, Canada.

Study Subjects: Study subjects were 685 persons who had been referred for a brief forensic psychiatric assessment to evaluate their competence to stand trial, and their suitability for treatment and/or a defense of insanity. Subjects were not representative of offenders as a whole. A high prevalence of mental illness was noted among the subjects, and over 80% had committed at least one violent offense.

Measures: Violent recidivism, psychopathy, schizophrenia, and alcohol abuse were the main variables of interest. The twenty-item Psychopathy Checklist was used to judge psychopathy. The presence of schizophrenia and alcohol abuse were determined from file reviews. Violent recidivism was defined as any criminal charge for an offense against another person or any return to a maximum security setting for such an act. Recidivism data were collected from the files of the Royal Canadian Mounted Police (RCMP), the National Parole Services, and the Lieutenant Governor’s Board of Review.

Main Findings: Violent recidivism occurred in 31% of the subjects. Psychopaths were more likely to have an alcohol problem and this combination was positively related to violent recidivism. Alcohol by itself was also related to violent recidivism. Persons with schizophrenia were less likely to relapse into crime.

Conclusions: Among persons at high risk of  violent recidivism, psychopaths are at a particularly high risk as are alcoholics. Persons with schizophrenia pose the least risk.

Methodological Critique: A 23% overlap between the two groups, when combined, was corrected for by including each individual only once. The sample was highly selected and non-representative of inmates in general. Further, authors did not control for previous violence, a known risk factor for subsequent violence.

Causality: Given the highly selected nature of the sample, no general statement can be made concerning a causal link between mental illness and violence. However, the inverse relationship between schizophrenia and violent recidivism is interesting.

Siomopoulos, V. (1978). Psychiatric diagnosis and criminality. Psychological Reports, 42, 559-562.

Purpose and Objective: To examine the distribution of various offenses among several psychiatric diagnoses.

Research Design: Case series-convenience sample.

Setting: Maximum-security forensic unit in a State Hospital in a large city of the United States of America.

Study Subjects: Study subjects were individuals facing criminal proceedings on serious charges and found not fit to stand trial. Subjects were examined independently by two psychiatrists. Where discrepancies between the psychiatrists occurred, a re-evaluation was conducted (by both psychiatrists) to arrive at a consensus. Socio-demographic data, diagnoses, and type of offense were collected.

Measures: None were given but diagnoses were most likely arrived at through regular psychiatric interviews.

Main Findings: Schizophrenia was the most frequent diagnosis among the total population and among those in each category of offense, except arson which was most often found among individuals diagnosed with manic-depressive illness. Substance abuse was commonly found to occur with other diagnostic categories.

Conclusions: Schizophrenia was found to be common among felons.

Methodological Critique: This study is problematic for a number of reasons, including the fact that a non-probability and highly selected sample on both mental disorder and severity of offense was used. In addition, instruments were non-standardized and the confounding effects of substance abuse were not controlled.

Causality: A causal inference cannot be made on the basis of these findings.

Strick, S.E. (1989). A demographic study of 100 admissions to a female forensic center: Incidence of multiple charges and multiple diagnoses. The Journal of Psychiatry and the Law, Fall, 435-448.

Purpose and Objective: To describe the characteristics of women admitted to a female forensic centre.

Research Design: Descriptive review of a case series of records.

Setting: A female forensic facility in a State Hospital in the United States of America.

Study Subjects: Study subjects were the first 100 females admitted from all areas of the state in which the hospital was located.

Measures: ICD-9 and DSM-III criteria were used for diagnoses.

Main Findings: Seventy-nine percent of the sample was psychotic on admission, mostly suffering from schizophrenia. The nature of offenses were mostly against persons.

Conclusions: A large segment of women in the study suffered from severe mental illness.

Methodological Critique: This is a simple descriptive study with no attempts at making correlations among the different variables. Therefore, the study cannot be used to make any statements about causality. However, the results (showing a high prevalence of mental disorder) are consistent with other more controlled studies.

Causality: A causal inference cannot be made on the basis of these findings.

Taylor, P.J. (1986). Psychiatric disorders in London’s life-sentenced offenders. British Journal of Criminology, 26(1), 63-78.

Purpose and Objective: To evaluate the adjustment of persons serving life sentences (“lifers”) to community supervision.

Research Design: Cross-sectional survey.

Setting: Probation Services, Inner London, England.

Study Subjects: Probation officers were asked to complete a questionnaire regarding persons serving life sentences under community supervision.

Measures: A forty-nine item questionnaire, designed by the author was provided to probation officers. It covered demographic details, psychiatric symptoms, diagnosis, and role of alcohol or psychiatric symptoms in the life-sentence offense.

Main Findings: Two-thirds of lifers obtained a diagnosis (9% schizophrenia, 13% depression, 33% alcohol abuse, 33% personality disorder). Thirty-three percent of lifers were recalled from community placements for violations.

Conclusions: Most forms of psychiatric disturbances were distributed evenly between those lifers who had murdered and those with any other kind of offense. Violent reoffending was unusual.

Methodological Critique: It is not clear how probation officers made or recalled psychiatric diagnoses.

Causality: Because this is a cross-sectional  study of a selected group of subjects with no basis of comparison, no statement can be made regarding a casual relationship between mental illness and violence.

Taylor, P.J. and Gunn, J. (1984). Violence and psychosis. British Medical Journal, 288, 1945-1949.

Purpose and Objective: To examine the prevalence of violence and mental illness and the relationship between the two.

Research Design: Cross-sectional survey of records (prevalence).

Setting: The largest prison in Europe located in south London, England.

Study Subjects: The authors do not specify how they selected their sample. However, two groups of men, violent offenders, and those being held at the prison hospital, were studied. All were admitted during the months of June, September, and December, 1979, and March, 1980. In total, 1241 men were selected.

Measures: A special checklist was devised to collect data from records. Diagnoses were made according to ICD nosology.

Main Findings: The prevalence of psychiatric symptoms on admission to prison was 9.0%. A further 8.6% experienced symptoms of withdrawal from alcohol or drugs. Serious personal and life threatening violence was more commonly committed by normal prisoners whereas arson and property crime were more often committed by those who were mentally ill. A high proportion of violent offenders were schizophrenic (11% committed homicide and 30% committed arson) compared to those in the general population in Greater London (0.1-0.4%).

Conclusions: The prevalence of mental illness in prison is high. Offenses are mostly against property, but offenders suffering from schizophrenia are overly represented among the violent crimes.

Methodological Critique: This is a cross-sectional survey based on records. The sample selection is not specified so it is not clear whether the results are representative of all offenders. The sample is highly selected for crime and for mental illness given the overlapping categories of violent and hospitalized men. This may have been the reason for the over-inflated results on mental illness and violence.

Causality: A causal inference cannot be made on the basis of these findings.

Teplin, L.A. (1990). Detecting disorder: The treatment of mental illness among jail detainees. Journal of Consulting and Clinical Psychology, 58(2), 233-236.

Purpose and Objective: The aim of this study was to investigate the extent to which mentally disordered offenders are treated while they are in the custody of the criminal justice system.

Research Design: A cross-sectional survey design.

Setting: A prison in a large metropolitan  area in United States of America.

Study Subjects: All post-arraignment detainees, regardless of previous psychiatric morbidity, history of substance abuse, intoxication, potential for violence, or status on fitness to stand trial, were randomly selected, and stratified for type of charge (misdemeanour/felony).

Measures: A structured Diagnostic Interview Schedule was used to arrive at DSM diagnoses to operationalize “true” mental illness for purposes of deciding need for treatment. In addition, two criminality variables were collected: severity of offense (misdemeanour/felony); and the nature of the offense (violent/nonviolent). Social status variables (age, education, employment status, race, and income) were also collected. The detection of mental illness by prison personnel was conducted independently of the assessment by the researchers.

Main Findings: In decreasing order of contribution to the model, the following variables contributed significantly in a log-linear Logit model to the likelihood of detection of mental illness and, hence, provision of treatment: treatment history (91.7% detected, by far the most important predictor), overt behaviour problems, nature of arrest, depressive symptoms, and schizophrenia.

Conclusions: The overall rate of detection of mental illness by prison personnel was very low with 32.5% indicating poor provision of treatment for mentally ill offenders.

Methodological Critique: A representative sample of all post-arraignment cases is a major strength, but, given that all of these cases were post-arraignment, there is a selection bias towards severe problems, both clinically and criminally. In addition, the number of interviewers was not given and inter-rated reliability issues were not discussed.

Causality: A causal inference cannot be made on the basis of these findings.

Teplin, L.A., Abram. K.M. and McClelland, G.M. (1994). Does psychiatric disorder predict violent crime among released jail detainees? American Psychologist, 49(4), 335-342.

Purpose and Objectives: This study examines whether post-release arrest rates for violent crime are a function of mental disorder.

Research Design: A six year follow-up study of arrestees detained between November 1983 and November 1984.

Setting: Cook County, Chicago, Illinois, United States of America.

Study Subjects: A stratified random selection of 728 male arrestees who had undergone pre-trial arraignment. Stratification was done to insure that sufficient numbers of persons with serious charges would be  included for study. Analysis was conducted based on 644 subjects. Those with cognitive impairment, those who had died during the follow-up period, and those with missing arrest records were excluded.

Measures: Severe mental disorder was considered to include schizophrenia or major affective disorders. In addition, subjects with substance abuse disorders or psychotic symptoms were included for study. Diagnostic data were obtained in face-to-face interviews using the structured Diagnostic Interview Schedule (DIS) for DSM disorders. Arrest data were collected from police records and matched to subjects using their unique identification number assigned to them by the Department of Corrections. This information included charges laid outside of the county. Violent crimes were considered to include assault, aggravated assault, battery, aggravated battery, murder, attempted murder, manslaughter, robbery, unlawful restraint, armed violence, cruelty to children, criminal sexual assault, rape, deviant sexual assault, aggravated criminal sexual assault, and kidnapping.

Main Findings: Persons without a disorder had a .48 probability of being arrested for any violent crime during the six years of follow-up compared to .43 for persons with a severe mental illness, and .46 for persons with a substance abuse disorder. These differences were not significant. Similarly, no significant differences were found for major violent crimes. Considering the ratio of the number of arrests to the time at risk, no differences were noted for any violent crime or a major violent crime between the study groups. In every diagnostic group, persons with a prior history of violent crime were about twice as likely to be re-arrested during the follow-up period compared to those with no prior history. When prior criminal history was controlled, differences were still not noted between persons in the various disorder groups compared to those in the non-disorder group. These findings also held up when age was statistically controlled. Persons with either hallucinations or delusions did not have a higher probability of arrest upon release. However, persons with both hallucinations and delusions did have a slightly higher number of arrests for violent crimes but this was not significant.

Conclusions: Study subjects were highly recidivistic with almost half being re-arrested for a violent crime in the follow-up period. Psychiatric disorder did not increase the probability of being arrested for a violent crime. A history of both delusions and hallucinations increased the number of arrests for violent crimes but not significantly. The most influential predictor of subsequent violent crime was past violent crime.

Methodological Critique: This is a carefully conducted and well reported study. A major strength is that the analysis took into consideration the time that each offender was at risk of a violent crime (e.g. his time in the community). Probabilities of re-arrest were provided with 95% confidence intervals, making it possible to  determine the lower and upper range of plausible values for any given estimate.

Causality: As the authors note, because this study focuses on a selected group of offenders, it cannot be used to assess whether mental illness causes violence in the general population.

Toch, H. and Adams, K (1989). The disturbed violent offender. New Haven: Yale University Press.

Purpose and Objectives: To examine the relationship between mental illness and criminality, in particular, violent offenses.

Research Design: Record linkage study.

Setting: New York State Department of Correctional Services and New York State Mental Health Services, United States of America.

Study Subjects: Computer records of 8,379 inmates in the Department of Corrections were matched to their records in the Mental Health Services, spanning several years.

Measures: The researchers culled information on demographics, criminological variables and mental illness from the computerized records at the two agencies.

Findings: Of the inmates studied, 13.8% of those without a psychiatric history or history of substance abuse had a history of recent (within 3 years) violence and remote (3 years or more) violence. By comparison, 17% of those with a history of mental illness or substance abuse had a history of recent and remote violence. Percentages for the two groups in regard to remote violence only, were 30.9% and 51.1% respectively. Furthermore, 5.8% of inmates with a combination of psychiatric history and substance abuse committed unmotivated violent acts, compared to only 1.2% among inmates without a psychiatric history or history of substance abuse.

Conclusions: Inmates with a history of mental illness or a history of substance abuse are more prone than inmates without such a history to commit act of recent and remote violence and unmotivated violent acts.

Methodological Critique: This is one of the best studies using records not only because of the massive sample, but also because of the care the investigators took to collect and analyze the data. However, the study was compromised by shortcomings common to secondary data analysis stemming from a review of records taken over a long period of time, and from multiple raters across different organizations and institutions and social agencies with dissimilar aims and functions. The study results were also affected by the uneven quality of the records. Additionally, the authors did not always indicate where major assumptions were being made, nor did they describe the diagnostic composition of the mental patients they studied. Where diagnoses were provided, the authors did not comment on the quality of clinical data made by multiple clinicians at many different institutions and agencies. Finally, as the information was gathered from records in New York State only, it is possible that many could have been admitted to correctional or mental institutions in other states.

Causality: Given that the authors studied selected sample of inmates, results from this study cannot be used to make any judgement about the causal relationship between mental illness to violence.

Valdiserri, E.V., Carroll, K.R. and Hartl, A.J. (1986). A study of offenses committed by inmates in a county jail. Hospital and Community Psychiatry, 37(2), 163-166.

Purpose and Objective: To study type of offenses among mental patients in prison.

Research Design: Review of files for a period of one year, February 1, 1982 to January 31, 1983.

Setting: On-site mental health clinic in a prison located in Pennsylvania, United States of America.

Study Subjects: All files of individuals referred to the psychiatric clinic (769 subjects and 853 separate referrals) representing 30.1% of the total admissions to the prison during the study period. These referrals were divided into two groups: psychotic (132 subjects and 156 separate admissions); and non-psychotic (639 inmates representing 697 admissions).

Measures: Data were abstracted from prison files.

Main Findings: General morbidity (prevalence) amounted to 5.51% of the total prison admissions. No demographic differences were noted between the two groups. Psychotic inmates were four times more likely to have been charged with minor offenses than non-psychotic inmates. No difference between the two groups regarding number of violent offenses was noted.

Conclusions: The psychotic offenders represent a seriously ill population. The lesser category of charges gives support to the “criminalization” hypothesis.

Methodological Critique: This is a review of clinical records of a highly selected sample compiled by many clinicians in a busy prison system. The report did not give details on how diagnoses were obtained, and was all encompassing in calling all mentally ill inmates “psychotic” without any breakdown of the conditions of interest. This study made no claims, and none can be made, about causality.

Causality: A causal inference cannot be made on the basis of these findings.

Yarvis, R.M. (1990). Axis I and Axis II diagnostic parameters of homicide. Bulletin of the American Academy of Psychiatry and the Law, 18(3), 249-268.

Purpose and Objective: To study overall patterns of psychopathology.

Research Design: Case series design.

Setting: A private clinical practice specializing in legal assessments.

Study Subjects: One hundred subjects charged with homicide out of 219 referred to the author for the  period January 1, 1980 to December 31, 1988.

Measures: In-depth psychiatric interviews using DSM-III criteria augmented by a review of records.

Main Findings: Substance abuse (35%) and psychotic disorders (schizophrenia 21% and affective disorders 8%) accounted for most of Axis I diagnoses, whereas 40% had a diagnosis of Axis II antisocial personality disorder.

Conclusions: Murderers were found to be a heterogenous population manifesting different prevailing diagnostic patterns according to a combination of factors such as sex, age, criminal history, and relationship to victim.

Methodological Critique: This was a highly selected sample of individuals specifically referred because of presumption of mental problems. This was not a representative sample and the denominator for all cases appearing in courts during the study period is not known. Iin addition, no standardized instruments were given.

Causality: A causal inference cannot be made on the basis of these findings.

Other Empirical Studies of Interest

The following empirical studies raise key methodological points that have implications for drawing causal inferences as identified in the “Comment” sections that appear at the end of each of the following structured abstracts.

Cirincione, C., Steadman, H.J., Robbins, P.C. and Monahan, J. (1994). Mental illness as a factor in criminality: A study of prisoners and mental patients. Criminal Behaviour and Mental Health, 4, 33-47.

Purpose and Objectives: To compare long-term patterns of crime among mentally disordered offenders and prison inmates. The main hypothesis under investigation was that criminological variables would be the best predictors of subsequent criminality.

Research Design: Research presented is based on subjects previously studied and reported on in 1984. A historical cohort study design was used with a follow-up period of eleven years.

Setting: New York State, United States of America.

Study Subjects: Subjects were identified from admission records of males under the age of 65 years admitted to New York State mental health facilities and prisons in 1968 and 1978. Study subjects comprised four cohorts: prisoners with no history of mental illness; prisoners with a history of mental illness; patients with previous arrests; and patients with no previous arrests.

Measures: Data describing subsequent arrests and hospitalizations were collected from archival sources.

Main Findings: In general, the 1978 cohorts showed higher arrest rates compared to the 1968 cohorts. With respect to subsequent arrests, prisoners in each era without previous hospitalizations were the most prone to re-arrest and patients with no arrest history were the least  likely. The hybrid groups had similar, intermediate levels of arrest, falling in between the other two groups. Similar patterns were noted for violent crimes. Mental patients with no prior arrests were somewhat less likely to be arrested than the general population.

Conclusions: Arrest history is a stronger predictor of subsequent crime than is a history of state mental hospitalization. Prisoners with no prior hospitalizations pose the greatest threat of subsequent violence and criminality.

Comment: This study confirms the importance of controlling for arrest history when assessing the relationship between mental hospitalization and criminality—something which few studies have taken into consideration.

Harry, B. (1985). Violence and official diagnostic nomenclature. Bulletin of the American Academy of Psychiatry and the Law, 13(4), 385-388.

Purpose and Objective: To assess the degree to which the belief in the positive association between mental illness and violence has been accepted.

Research Design: Content analysis of DSM psychiatric nomenclature used between 1952 and 1980.

Measures: The proportion of disorders with descriptive words or diagnostic criteria that contain references to violence in the various versions of official psychiatric nomenclature (DSM-I, DSM-II, and DSM-III). Violence was defined as including both violence to self and violence toward others.

Main Findings: Less than 3% of disorders in DSM-I and DSM-II contained words or criteria indicating violent behaviour. This jumped to 46.6% in DSM-III. Considering only diagnostic criteria, 26.2% of disorders in DSM-III contained words relating to violence. The diagnostic groups with the largest number of violent disorders included substance use disorders, organic mental disorders, affective disorders, and disorders occurring during childhood.

Conclusions: The percentages of mental disorders officially described or defined in terms of violent acts has increased, blurring the boundary between mental illness and violence and confounding any relationship between the two.

Comment: This study has important methodological implications for the apparent increasing finding of an association between mental disorders and violence that has appeared in the recent literature (e.g. last 15 years), but not prior to that time. Furthermore, it calls into question the ability of researchers to define mental illness independently of violence for the purposes of study, particularly when using DSM-III (or presumably subsequent) nosological systems.

Harry, B. and Steadman, H.J. (1988). Arrest rates of patients treated at a community mental health center. Hospital and Community Psychiatry, 39(8), 862-866.

Purpose and Objective: The purposes of this  study were to: (a) ascertain the arrest rates of inpatients, outpatients, and emergency patients after their first known contact for treatment at a community mental health centre; and (b) determine if the predictors of arrest among state hospital populations, reported in the literature, are the same for community mental health populations.

Research Design: A historical cohort design with a variable follow-up depending on the study entry date. Subjects were followed through to October 1984 giving an average of nine years of follow-up for the 1975 cohort and one year of follow-up for the 1983 cohort.

Setting: A comprehensive community mental health centre in a small city in Missouri, United States of America.

Study Subjects: Study subjects were randomly selected from the records of all adult patients admitted to the centre in 1975 and 1983, where their admission was their first known psychiatric contact. First psychiatric contacts were identified by noting patients’ self-reports and by checking statewide records for previous contacts with other state-supported mental health facilities. A total of 200 inpatient, 181 outpatient, and 186 emergency first admissions occurred during 1983 only. Census data were used for the local ten county catchment area to calculate population values.

Measures: Data on social and clinical factors were abstracted from the health records. Diagnoses reflected DSM-III terminology. State-wide adult criminal arrest records were obtained for each subject through to October 1984. Violent crimes were considered to be homicide, assault, and child battering. Potentially violent crimes were robbery and weapons violations. Sexual crimes were rape, sodomy, and sexual abuse.

Main Findings: Findings reported in this paper were incorrect. Corrections appear in a subsequent Letter to the Editor [Harry, 1989, Hospital and Community Psychiatry, 40(12), 1303. The corrected findings are presented below. The fundamental conclusions of the paper were unchanged by these corrections.

One-year arrest rates per 1,000 for the 1983 cohort revealed that inpatients were arrested with the highest frequency (78/1,000), followed by emergency patients (53.5/1,000), then by outpatients (36.6/1,000) Similarly, in the 1975 cohort, inpatients were arrested at a higher rate (41/1,000) compared to 40/1,000 for outpatients. No emergency data were available for this year. Factors that were found to predict arrest were the diagnosis of antisocial personality disorder, number of prior arrests, and younger age, however, together, these variables explained only 5% of the total variation. Most of the arrests were for non-violent offenses.

Conclusions: Community mental health centre patients were found to have arrest rates that were substantially lower than rates reported in the literature for state hospital patients. As persons with mental illness  treated in a broad spectrum of mental health settings are included in the analysis of arrest rates, the discrepancy between arrest rates of patient samples and the general population will be reduced.

Comment: Given that the bulk of studies have followed hospitalized cohorts, this study adds an important dimension to this area of knowledge, especially given the emphasis on community mental health care. This study quantifies the magnitude of selection bias that can be expected when different psychiatric populations are used as study cohorts and reinforces the need to construct cohorts that are representative of all persons with mental illness.

Lagos, J.M., Perlmutter, K. and Saexinger, H. (1977). Fear of the mentally ill: Empirical support for the common man’s response. American Journal of Psychiatry, 134(10), 1134-1137.

Purpose and Objective: The authors examined hospital records of psychiatric patients to determine how frequently people behave violently when they become mentally ill.

Research Design: Cross-sectional survey of hospital records.

Setting: New Jersey, United States of America.

Study Subjects: Study subjects comprised a random sample of 400 patients admitted during 1974, 100 to each of the 4 psychiatric facilities in New Jersey.

Measures: Admission notes were reviewed for any description of violent behaviour that was recent and presented as part of the basis for admission. Behaviours included attacks on persons or objects, threats to persons, verbal attacks on persons, ambiguous violence (e.g. non-specific descriptions), and loss of impulse control.

Main Findings: Of the 400 admissions reviewed, 37.7% manifested some form of violent behaviour with 20% specifically acting violent toward other persons or objects. The percentage of individuals who were described as having attacked other persons varied considerably from hospital to hospital from a high of 21.6% to a low of 4.4%. Of the 115 mentally ill whose records showed violent behaviour, only 3 were arrested.

Conclusions: The authors conclude that there may be considerable violent behaviour associated with mental breakdowns. To be more accurate, they should have noted that there may be considerable violent behaviour associated with hospitalizations for mental illness.

Comment: This study was chosen for inclusion because it illustrates: (a) a high proportion of patients are admitted to hospital because they are violent; and (b) the proportion of violent patients varies considerably from hospital to hospital. This study illustrates the biases inherent in hospitalized samples of mentally ill. The finding that only 3 of the 115 violent mentally ill were arrested highlights the potential for errors due to misclassification when making causal inferences concerning  the relationship between mental illness and violence from institutional admission data describing hospitalizations or arrests. Not all violent acts are reflected in arrest statistics.

Steadman, H.J., Venderwyst, D. and Ribner, S. (1978). Comparing arrest rates of mental patients and criminal offenders. American Journal of Psychiatry, 135(10), 1218-1220.

Purpose and Objective: To compare the arrest rates of former mental patients and criminal offenders to the general population to determine if prior criminality, rather than mental illness, is the root cause of observed differences.

Research Design: Unspecified by authors. Data presentation suggests a follow-up design with a one year variable follow-up period (i.e. persons discharged during the latter part of the year would have had less opportunity to be arrested compared to persons discharged during the early part of the year).

Setting: Albany Country, New York, United States of America.

Study Subjects: The authors selected two groups of mental patients and two groups of criminal offenders. Subjects were all those released from psychiatric centres (N=307), jails, and prisons (N=419) in 1968 and 1975.

Measures: Subsequent arrests comprise the main outcome measure. Violent crimes are not analyzed separately.

Main Findings: When broad comparisons were made, ex-patients had higher arrest rates compared to the general population, and criminal offenders had arrest rates that were higher than those of ex-mental patients. However, when previous criminality was taken into consideration, a different pattern emerged among ex-patients. Ex-patients who were arrested prior to their hospitalization were arrested more often than the general population. Ex-patients with no prior arrests were arrested about as often or less often than the general population.

Conclusions: The authors conclude that as the composition of state mental hospital has changed to include more individuals with prior criminal arrest records, the rates of arrests for patient samples has increased. Those mentally ill patients who have not been arrested (almost 75%) are arrested about as often or less often than the general population. It is the patient with multiple prior arrests who is often re-arrested upon release from a mental hospital.

Comment: Despite the potential for underestimating arrest rates in both ex-patient and offender groups, this study is important from a methodological perspective because it raises the issue that it is prior criminality, not mental illness per se, that results in higher subsequent arrests rates. Based on this finding,  subsequent research should: (a) develop cohorts for study that are at risk for violence or criminality by excluding individuals from study with prior histories; or (b) statistically control for prior history in the analysis.

Straznickas, K.A., McNiel, D.E. and Binder, R.L. (1993). Violence toward family caregivers by mentally ill relatives. Hospital and Community Psychiatry, 44(4), 385-387.

Purpose and Objective: This study assessed features of family relationships among hospitalized psychiatric patients that are associated with family members becoming targets of violence.

Research Design: Retrospective review of a case series.

Setting: A university-based, locked, short-term psychiatric inpatient unit in the United States of America. Based on the affiliations of the authors, the unit may be located in San Francisco, although this is not specified in the text.

Study Subjects: Study subjects were 581 patients admitted to the unit between 1983 and 1990.

Measures: Diagnostic information was abstracted from hospital files according to the ICD-9-CM final diagnosis. Indications of physical attacks on others were based on specific mentions of assault (hitting, pushing, or choking) during the two weeks prior to admission. Additional socio-demographic, interpersonal, and clinical data were abstracted from the charts.

Main Findings: Nineteen percent of the patients (N=113) had physically attacked someone in the two weeks prior to their admission, and of this, 31 had attacked more than one person. Of the 113 patients who attacked someone, 50 assaulted people outside of the family, 10 patients assaulted both family members and individuals outside of the family, and 53 assaulted family members.

Comment: As well as reinforcing selection bias in hospitalized samples, this study highlights the fact that when persons subsequently hospitalized for a mental illness became violent, family members were the most likely target. Without suitable comparison groups, however, it is not clear whether the relatives of the mentally ill are more likely to be the targets of violence compared to the relatives of the non-mentally ill. Nevertheless, this study suggests that family education programs that include information on early warning signs of decompensation, and how to react to aggressive escalation in ways that can minimize risk and result in improved adjustment may be helpful.

Review Articles and Key Position Papers

The following articles either review the available literature or express innovative ideas regarding the interpretation of the literature. Many of the review articles are widely cited throughout the literature. Others are less frequently cited but convey important ideas or perspectives such as those that assess the applicability of findings to the Canadian situation. These reviews have not always used a critical, methodological perspective. At times, authors have accepted controversial findings with little scepticism. Despite these problems, these articles summarize a comprehensive list of publications relevant to the issue of mental illness and violence, and provide comprehensive references in the area. Because these are not empirical studies, a structured abstracting approach was inappropriate. Instead, key points that are relevant to the current critical review have been highlighted and, where appropriate, commentary has been provided.

American Psychiatric Association (1994). FACT sheet - violence and mental illness.

This fact sheet, designed for public consumption, summarizes what is known about the relationship between mental illness and violence. Recent research suggests that some mental illnesses increase the risk of violence, especially among patients with neurological impairments and psychoses, but that “chaotic, violent family environments in which alcohol or substance use is common, ongoing conflict among family members, and a controlling atmosphere (are) associated with violence by persons with mental illness”. The fact sheet also stresses that family members are at an increased risk of victimization by their mentally ill relatives rather than by the population at large, and that no clear-cut relationship exists between societal violence and the development of specific mental disorders.

Borzecki, M. and Wormith, J.S. (1985). The criminalization of psychiatrically ill people: A review with a Canadian perspective. The Psychiatric Journal of the University of Ottawa, 10(4), 241-247.

These authors review the various lines of argument and empirical studies undertaken in Canada and elsewhere that support the thesis that mentally ill persons are increasingly being criminalized through being diverted to the criminal justice system. Of special note is that Canadian data are provided to illustrate the deinstitutionalization of the mentally ill between 1962 and 1981. Data on government spending for psychiatric programs is shown to have increased over this time period and these authors argue that it is likely that much of these funds have been directed into short-term inpatient care. They suggest that these data indicate that the community mental health movement may not be as great a failure in Canada as it appears to have been in the United States. They caution that Canada may have superior community health facilities and, by virtue of a principle of universal access to inpatient and outpatient care, greater availability of appropriate services. Caution must, therefore, be exercised when generalizing findings from American studies to the Canadian situation.

Bradford, J. (1994). Violence and mood disorder: Forensic issues and liability concerns. The  Canadian Review of Affective Disorders, 5(2), 1-7.

This review on the issue of violence and mental illness contains a reference to the American Epidemiological Catchment Area studies, specifically the analysis of the data by Swanson et al. (1990) as to the independent role of psychosis as a trigger to violent behaviour. Bradford also mentions some of the PET (positron-emitting tomography) studies and those implicating low serotonin levels in violence. Bradford then addresses more specific forensic issues with respect to clinical aspects of violence in depression, management concerns, and legal liabilities, in particular, prediction and duty to warn.

Cohen C.I. (1980). Crime among mental patients—a critical analysis. Psychiatric Quarterly, 52(2), 100-107.

Cohen provides an excellent methodological critique of the literature, illustrating how previous research examining criminality among discharged mental patients has been characterized by methodological flaws. As a result, the question of whether former patients are more dangerous than the general public remains unanswered. Among the methodological difficulties noted were: (a) lack of comparability across studies with respect to time, setting, and geography; (b) a lack of control for pertinent confounding factors such as demographic variables or prior criminality; (c) some sample sizes too small to reliably detect rare events such as violence; (d) lack of differentiation among diagnostic categories; and (e) over-reliance on arrest records to measure crime without taking into consideration crimes committed or actual convictions. Cohen concluded that without more carefully controlled studies, we must be circumspect about attributing criminality to discharged mental patients.

Davis, S. (1991). An overview: Are mentally ill people really more dangerous? Social Work, 36(2), 174-180.

Davis provides an excellent methodologically-oriented review, highlighting problems in previous studies that have the potential to alter the conclusions of the studies. He argues that an objective and systematic study of the issue of mental illness and dangerousness is crucial to the formulation of appropriate and effective policies for the provision of community mental health services. Davis points out that it has become fashionable to imply that the mentally ill are somehow more dangerous than the non-mentally ill. Advocates for the mentally ill have pointed out that the media have exaggerated the crime rates of mentally ill people and have fostered this stereotype through selective reporting. While objective research will do much to resolve these issues, research in this area has traditionally been plagued by methodological problems. For example, most studies have focussed on biased samples of institutional populations who tend to be more disabled and “acting out” than the general  population of persons with mental illness. These studies may overestimate the relationship between mental illness and violence. Similarly, following released patients may underestimate the potential for violence because only those with the best prognosis will be released. Similarly, there have been problems in the definition and measurement of dangerousness. The majority of studies have used arrest rates. This is problematic because studies have shown that mentally ill persons may be arrested at a disproportionately higher rate than non-mentally ill persons, thus giving an over-estimation of the criminality of the mentally ill. A third problem is the lack of control for confounding factors that predict criminality in the general population (e.g. age, sex). When factors are considered appropriately, much of the difference in mentally ill and general population groups disappears. A small criminal subset who may have been inappropriately diverted into the mental health system may account for the majority of crime. Given present research, Davis concludes that the answer to the question of mental illness causing violence remains inconclusive.

Davis, S. (1991). Violence by psychiatric inpatients: A review. Hospital and Community Psychiatry, 42(6), 585-590.

Davis begins his review of the literature on inpatient violence with an analysis of the incidence, prevalence and changing rates of inpatient violence. He then categorizes the factors affecting these rates into three categories: (1) individual; (2) situational; and (3) structural. In regards to the incidence and prevalence of inpatient violence, Davis concludes that variations in methodology have made it difficult to determine the extent of violence in psychiatric facilities. He explains that studies of inpatient violence are hard to compare because of differing definitions of violence, and the variety of settings in which the studies have taken place ranging from general hospital to psychiatric to forensic facilities. In general, the rates of inpatient aggression have ranged from 2.54 assaults per bed per year to 7-10% of patients involved in assaults during a 1-3 month period of observation. Overall, serious assaults are rare. A number of researchers have found that a majority of the incidents are conducted by a minority of patients.

Cross-cultural comparisons indicate that rates of violence tend to be higher in the United States than in other countries. One study for example showed that the total number of violent incidents during one year in the 28 New York State psychiatric facilities totalled 2,000, compared to only 311 violent assaults in all similar British facilities over 3 1/2 years. Davis concludes that studies have revealed several factors that may be predictive of violence in inpatient settings. Among them are the presence of psychosis and phase of illness. Compared to age and a history of violent behaviour, sex may not be a very useful discriminating factor. At the institutional level, a certain amount of violence may be inevitable in the process of  dealing with involuntary, treatment-resistant patients. Factors such as overcrowding, provocation from staff and other patients, staff expectations and inexperience, and poor management practices may affect violence. Factors at the structural level such as a shortage of beds and community resources may also affect the occurrence of violence.

Based on the evidence thus far, violence appears to be the result of an interaction of multiple factors. A model of violence is presented, which considers a variety of factors including clinical, individual, situational and structural factors.

Davis, S. (1992). Assessing the “criminalization” of the mentally ill in Canada. Canadian Journal of Psychiatry, 37, 532-538.

Davis indicates that no studies on the criminalization of the mentally ill have been conducted in Canada and cautions that American findings may not be generalizable to this country. He analyzes the factors that contribute to the American findings and provides a detailed account of the extent to which these might also be operating in Canada. For example, deinstitutionalization, coupled with the absence of community support systems, is widely agreed to have placed greater numbers of patients at risk of perpetrating violence while in the community. In Canada in 1955, 4.24 patients per 1,000 were hospitalized; this had decreased to 0.7 by the early 1980’s. However, Canada’s universal health care system may provide for greater access to community services than in the American setting. Davis also examines the role of police in diverting mental patients to emergency resources and discusses the “psychiatrization of criminals” thesis as one explanation for the higher prevalence of mental illness among incarcerated offenders. In general there is a paucity of Canadian research bearing on these issues. To fully assess these trends, more Canadian research will be necessary.

Garza-Treviño, E. (1994). Neurobiological factors in aggressive behaviour. Hospital and Community Psychiatry, 45(7), 690-699.

This is a review of the literature on the neurosciences and psychiatric clinical research about biological factors in aggression in neuropsychiatric syndromes. The author conducted a computer search of publications on the neurobiological components of aggression published in the past 25 years (1977-1993). Studies were divided into four groups: (1) animal models of aggression using EEG recordings during chemical and electrical stimulation of areas of the brain; (2) EEG studies of human brains in normal and pathological states; (3) neuropathological and neuroimaging studies using CAT, MRI and PET (positron-emitting tomography) to detect morphological abnormalities in brains of abnormally aggressive subjects; and (4) neuropsychological studies of the prevalence of psychological impairments among recurrently violent mentally ill patients.

The author concludes that aggressive behaviour accompanying psychopathological states is multidetermined. With the exception of psychosocial or economic influences, possible causes of such aggression include lesions to inhibitory centres of the brain, chemical stimulation of rage centres through drugs or seizures, subtle molecular damage to receptors that may be hereditary or acquired, or dysfunction of neuronal networks. Studies suggest that aggressive behaviour is associated with: (1) damage to centres of the brain located in the limbic structures, temporal lobes, and frontal lobes apart from possible damage to connections between the amygdaloid complex and the hypothalamus and between the hyppocampal cortex and the frontal lobes; and (2) deficiency or dysregulation of serotonin, “low serotonin syndrome”, and potentially other neurotransmitters such as norepinephrine, dopamine and glucose. In addition, effects of seizures, drugs and alcohol seem related to alteration of inhibitory mechanisms and subsequent release of pre-existing behavioural patterns through a process of kindling.

Gunn, J. (1977). Criminal behaviour and mental disorder. British Journal of Psychiatry, 130, 317-329.

Similar to Mesnikoff and Lauterbach (1976) (see below), Gunn provides a detailed summary of previous findings, but without a serious methodological critique. Nevertheless, he does identify problems in defining violence and criminality, as well as the selective view resulting from the focus on institutional populations that systematically exclude the bulk of mental patients or criminals. He concludes that it is probably best to avoid generalizations about mental disorder and criminality and focus, instead, on specific behaviour problems associated with specific disorders.

Haller, R.M. and Deluty, R.H. (1988). Assaults on staff by psychiatric inpatients: A critical review. British Journal of Psychiatry, 152, 174-179.

The paper reviews the literature concerned with assaultive acts committed by psychiatric patients during hospital stay, and with the contextual factors and patient characteristics associated with such assaults. Based on the findings, the authors attribute increased risk of assault to a variety of factors: (1) understaffed units; (2) deinstitutionalization; (3) an increasing number of readmissions and involuntary admissions; (4) patients’ right to refuse medication, often leading to an increase in patient/staff confrontations; (5) diverse mixtures of patients and; (6) patients being younger and more difficult to manage than in past years. Although assaults on staff have apparently increased in recent years, a number of studies indicate that the vast majority of psychiatric patients are not assaultive. There appears to be a small core of patients, typically 7-10% of the total population, who display assaultive behaviour that is dangerous enough either to be worthy of mention in nursing reports, or to  cause an injury and therefore require the completion of an injury report.

Hodgins, S. (1994). Editorial: Schizophrenia and violence: Are new mental health policies needed? Journal of Forensic Psychiatry, 5(3), 473-477.

Hodgins suggests that evidence is mounting to indicate that patients with schizophrenia are likely to engage in aggressive behaviour toward others when in the community and she summarizes several lines of evidence supporting this position. She argues that the community mental health movement which closed mental hospitals and treated persons suffering from major mental disorders in the community can be considered to be a failure. Polices governing the treatment of persons suffering from schizophrenia must be developed taking into account the public’s right to safety, although Hodgins does not specify what these policies might be.

Link, B.G. and Stueve, A. (1995). Evidence bearing on mental illness as a possible cause of violent behaviour, Epidemiologic Reviews, 17(1), 172-181.

This is an excellent and up-to-date review of the literature on this subject. The authors point out that there are three reasons why it is important to establish whether or not there is a relationship between mental illness and violence: public safety; quality of life and well being of mental patients; and the consequences for those who commit violent acts (lawsuits, prison, et cetera).

The authors indicate that several types of studies point towards the presence of a relationship between mental illness and violence. The list of these studies and the comments of the authors are outlined as follows:

(1)

Arrest-rate studies of discharged psychiatric patients. Criticism of these studies fall into three categories: “criminalization of mental illness” whereby the arrest rates tell more about the arrest process than about an association between mental illness and criminality; “psychiatrization of criminal behaviour”, i.e., a tendencey to attribute a psychiatric diagnosis to behaviours that were previously considered to be predominantly antisocial and criminal; and “design” issues in studies that compare mental patients from public facilities (i.e. highly selected) with rates in the general population.

(2)

Conviction rate studies of birth cohorts based on case registers (such as the studies in the Scandinavian countries). These studies have shown a higher risk of criminality among individuals who suffer from mental conditions. Link and Stueve note that although birth cohort studies have better generalizability than arrest-rate studies, they suffer from an inability to account for the temporal ordering of factors (which comes first, criminality or mental condition) and hence cannot be used to infer  cause.

(3)

Arrest-rate studies based on a prevalence study of mental disorder (such as some of those conducted within the Epidemiological Catchment Area studies). This type of study observes community-dwelling respondents and investigates whether those with a history of mental illness are more likely to report a history of arrest. These population-based studies avoid selection biases and allow for the study of multiple confounding factors. However, temporal ordering of factors, unspecified criminality (as opposed to just violent behaviour) and lifetime prevalence measures of some mental disorders are considered weaknesses of this type of study.

(4)

Studies that incorporate self-reported violent behaviour while using community controls (such as some studies conducted within the Epidemiological Catchment Area studies). Contrary to the first three types of studies that depend on arrest rates, studies on self-reported violence do not necessarily involve arrest and are, therefore, more comprehensive. According to the authors, differences in violent behaviour between patients and non-patients as provided in these studies “are not artifactual but real”. The authors, however, indicate that these studies suffer as well from methodological weaknesses and unclear ordering of temporal factors.

(5)

Studies of “threat/control override” symptoms. These are theory-driven studies purporting to show an association between mental illness and violence when there is a perception of threat and/or override of personal controls. The authors argue that this type of study controls factors such as social desirability and temporally ordered variables and give, therefore, strong support to an association between mental illness and violence.

The authors conclude their review by indicating that there are four perspectives on the association of mental illness and violence: (a) that there is no association, let alone causal, and that this is refuted by mounting evidence to the contrary; (b) that there is an association but that it is spurious because of methodological limitations. However, this is counteracted by consistency of findings across studies so that the limitations in some are controlled by the strengths in others and vice versa; (c) that the association is causal and that this is proven by the consistency of the findings across different methodological approaches and by failure of an alternative, competing hypothesis; and (d) there is an association but it is mediated by multiple social factors. The authors indicate that this perspective could very well provide the explanation needed for the association, and that “it is possible that mental illness only leads to violent behaviour under certain conditions”. This context, they conclude, “deserves further scrutiny and specification”.  Finally, the authors recommend epidemiological studies with better measures and more adequate designs. Specifically, they recommend an epidemiological cohort design that (a) specifies the mental disorder(s) of interest, (b) follows representative samples of people with no history of the mental disorder(s) of interest and people experiencing the first episode of the disorder(s), and (c) compares the subsequent involvement of the groups in violent acts.

Mesnikoff, A.M. and Lauterbach, C.G. (1976). The association of violent dangerous behaviour with psychiatric disorders: A review of the research literature. Journal of Psychiatry and the Law, 3: 415-445.

These authors provide a detailed summary of research in four areas: (a) psychiatric disorders among criminal offenders; (b) violence among former psychiatric inpatients; (c) violence related to organic brain dysfunction; and (d) prediction of violence occurring among psychiatric patients. Interestingly, they note that studies conducted prior to 1960 show that ex-patients have rates of violent criminal behaviour that are no greater, or smaller than the general population. Later studies report that psychiatric patients released into the community display as much violent crime and, in some groups, more, than the general population. Unfortunately, the authors do not critically assess the methods used in these studies. No explanation is given for the discrepancy in findings between early and later studies.

Monahan, J. (1984). The prediction of violent behaviour: Toward a second generation of theory and policy. American Journal of Psychiatry, 141(1), 10-15.

Monahan traces generations of research work aimed at predicting violence among the mentally ill. First generation studies, conducted during the 1970’s, illustrated that mental health providers were not able to predict violence or dangerousness with any degree of accuracy. Even under ideal circumstances with detailed evaluations, they were wrong twice as often as they were right. Many took this research as supporting the argument to change the dangerousness criteria upon which most civil commitment legislation was based. In the criminal justice system, this research raised serious questions about indeterminate sentences for defined dangerous offenders. Second generation research has acknowledged that if it is not possible to predict violence in general, it may still be possible to predict violence with acceptable accuracy in certain circumstances. Thus, second generation thinking is characterized by a guarded optimism that some improvements in clinical predictions are possible. Monahan argues that future research should move into the realm of actuarial predictions that are designed to include relevant clinical and situational variables. In addition, research should be focused on developing short term predictions of violence among community samples.

Monahan, J. (1992). Mental disorder and violent behaviour. American Psychologist, 47(4), 511-521.

Monahan and Steadman’s 1983 article (see below) set the stage for disclaiming a relationship between mental illness and violence. Monahan has since changed his view. This paper provides the evidence and the inferences he has used to change his thinking on the issue. He begins by examining perceptions of mental illness and violence in history and in other cultures, noting that a link between these two has endured throughout time and across many different social settings. He notes that modern conceptions of mental illness and violence may be shaped by television where it has been found that 17% of prime-time American television dramas depict a character as mentally ill and, of these characters, 73% are portrayed as violent (compared to the 40% of non-mentally ill characters). Twenty-three percent of the mentally ill characters are depicted as homicidal compared to 10% of the non-mentally ill. Regarding professional perceptions, Monahan suggests that only mental health advocacy groups and behavioural scientists believe that the mentally ill are no more violent than the non-mentally ill.

Monahan then summarizes the findings of studies in a number of areas looking at the (a) prevalence of violent behaviour among persons with mental disorder among patient samples and community samples, and (b) prevalence of mental disorder among persons committing acts of violence, among criminal offenders and among community samples. As studies in each of these areas demonstrate a relationship, Monahan concludes that mental illness may indeed be associated with violence.

Monahan, J. and Steadman, H.J. (1983). Crime and mental disorder: An epidemiological approach. In, Tonry, M. and Morris, N. (Eds.). Review of research (Vol. 4, pp. 145-189). Chicago: University of Chicago Press.

See also: Monahan, J (1992). Mental disorder and violent behaviour. American Psychologist, 47(4), 511-521, (previous entry)

See also: Monahan, J. (1993). Mental Disorder and violence: Another look. In Hodgins, S. (Ed.). Mental disorder and crime (pp. 287-302). Newbury Park: Sage Publications for a similar review.

This study has remained one of the most influential among those supporting the notion that there is no relationship between mental illness and criminality. The authors adopt an analytic epidemiological framework to understand the relationship between mental disorder and crime. They draw an important epidemiological distinction: the difference between the frequency with which mental illness and crime actually occur (i.e. the true rate) and the frequency with which both come to public attention (i.e. the treated rate). The complexities of arriving at appropriate definitions or indicators of true crime and true mental illness are discussed with reference to policy and procedural issues. These authors consider arrest to be one index of the true criminal behaviour but acknowledge that  many criminal acts are committed by persons who are never arrested. At the time of this review there was very little evidence that the rates of severe mental disorder among people arrested were higher than in the general population. Further, no studies had been completed surveying the prevalence of true mental disorder and criminality in the general population.

These authors concluded that there was no consistent evidence that the true prevalence rate of criminal behaviour among former mental patients exceeded the true rate of criminality in the general population. Moreover, the authors did not find consistent evidence to support the hypothesis that the true rate of psychotic disorders among incarcerated offenders was higher than in the general population, once socio-economic status was controlled. With respect to non-psychotic disorders, they conclude, albeit cautiously, that the true prevalence of non-psychotic mental disorders was higher among inmate populations than among class-matched community controls. No comparable conclusions could be drawn regarding the rates of psychiatric hospitalization among incarcerated offenders as there was no baseline community population data on psychiatric hospitalizations. There was some evidence that persons hospitalized for a mental disorder had been convicted and imprisoned for crimes at a somewhat higher rate than the general population but this was considered to be associated with confounding by demographic factors. Great variation was also noted in the subsequent arrest rates of different types of mentally disordered offenders, accounted for largely by prior criminal history and demographic characteristics. The main conclusion drawn by these authors is that when appropriate controls for demographic and other factors are made, rates of true criminality are unrelated to mental disorder.

Morissette, Louis (1986). Criminalité et violence chez les malades mentaux traités dans la communauté : prévention possible? L’Union médicale du Canada, 115, 690-744.

The author conducted a literature review to elucidate trends indicative of an association between mental illness and criminality, to provide some insights on prevention strategies, and to comment on pertinent legislation in Quebec regarding the treatment of the mentally ill. The author divided the literature into two periods, before and after 1965. He used 1965 as the dividing date because that was the year in which research was first published indicating that mental patients in the community had a larger risk of being detained than the general population, both for property and personal crimes. Up to 1965, the wisdom was that mental patients did not represent a larger criminality risk, and that their criminality was not serious. The conclusion after 1965 was that both rates of criminality and dangerousness were higher among community mental patients than among the population in general. Although psychiatric admission was not predictive of higher criminality, the increase in the arrest rates of mental patients was mostly due to psychiatrized criminals (mental patients with a history of criminality). Psychiatric patients with personality disorders and drug dependencies had a similar criminal profile to common criminals, and a similar recidivism rate. These patients shared common characteristics, usually being single young men, unemployed, poorly educated, and hailing from a deprived and disorganized home environment. The number of these patients had increased over the last several years and could explain the higher arrest rate of mental patients. The author indicates that although the criminality rate seems the same between psychotic patients and the general population, the fact still remains that it is impossible to deny that psychotic patients do commit serious violent crimes.

The author concludes by providing some practical clinical guidelines to prevent criminal behaviour among psychotic patients, and suggests changes to mental health legislation that could help prevent victimization through more appropriate legal controls.

Morrissey, J.P. and Goldman, H.H. (1981). The enduring asylum. International Journal of Law and Psychiatry, 4, 13-34.

These authors provide a social history of Worcester State Hospital in Massachusetts, United States of America, in order to illustrate the cyclical reforms that have occurred in the care of the mentally ill, from community to institution and back again over the past 150 years. The history of a hospital presents a microcosm of large trends in mental health care and serves as a basis from which a number of service delivery problems are identified. For example, the hospital was founded in an era of social reform in response to criticisms against the inhumanity of dealing with the mentally ill in almshouses and jails. The Worcester State Hospital became the prototype for public mental hospitals in America. By 1850, however, increasing emphasis had been placed on social control, and hospitalization became a major social control mechanism where the largest number of patients were housed at the lowest possible cost. By 1896, a second wave of reform had swept through the hospital with the appointment of Dr. Adolf Meyer and his transformation of the facility into a major teaching and research centre, completely altering the concept of a mental hospital. There followed successive waves of reform, including the community mental health movement, deinstitutionalization, demedicalization, and decentralization. The authors alert policy makers that without stable community funding, the public mental hospital will likely endure as a repository for the unwanted in society.

Mulvey, E.P. (1994). Assessing the evidence of a link between mental illness and violence. Hospital and Community Psychiatry, 45(7), 663-668.

Mulvey points out that evidence supporting a  relationship between mental illness and violence is a pivotal point in the debate concerning the appropriate use of involuntary hospitalization and in the design of community-based efforts to control violence by the mentally ill. Though clinical reports have documented that some persons act violently on the basis of irrational beliefs, past evidence has tended to be interpreted such that no strong or consistent effect linking mental illness to community violence was found. However, evidence coming from studies such as the ECA studies in the United States of America (see Swanson et al., 1990, page 49 of this report) have rekindled the debate. Given the importance of this issue for community services for mentally ill individuals, Mulvey argues for a very careful and considered evaluation of the available research. Findings from a number of empirical studies are summarized showing associations between mental illness and violence in a number of settings. However, Mulvey points out that no clear indication of causality has yet been made between them. Investigations of a different type than those undertaken to date will be required in order to sort out causal mechanisms, with more attention to statistical issues surrounding the determination of clinically relevant associations, greater attention to the use of appropriate comparison groups of community residents who are not mentally ill and demographically similar study groups, a broader consideration of potentially associated variables, more careful operationalization of terms (e.g. violence), and the development of plausible theories that link mental illness to violence. Mulvey concludes that the view that violence and mental illness are not linked in the community no longer seems tenable but the current state of research is not helpful in understanding what should be made of the relationship.

Mulvey, E.P., Blumstein, A. and Cohen, J. (1986). Reframing the research question of mental patient criminality. International Journal of Law and Psychiatry, 9, 57-65.

The ongoing interest in the relationship between mental illness and criminality is supported by a utilitarian need to understand the social consequences of deinstitutionalization policies, as well as a clinical need to develop guidelines for the prediction of dangerousness. Early studies (prior to the early 1960’s) consistently report a low risk of criminality among mental patients, about one-fifteenth of the general population rate. These findings are likely a result of selective release criteria (where low-risk individuals were released from hospitals) and strict community supervision. Subsequent to the 1960’s, studies have tended to find an increased risk of criminality among mental patients. The arrest rates of mental patients appear to have increased and prior arrest appears to have considerable influence on the likelihood of post-release arrest. Most studies show that mental patients with no prior arrest history have post-hospital release arrest rates that  are lower than the general population. Recent evidence indicates that individuals with multiple prior arrests are much more likely to be subsequently arrested compared to those with only a single previous arrest. These findings suggest that there may be a small number of active offenders in the mental patient population that account for the generally higher arrest rates. These authors argue that greater knowledge of this group of offenders is essential for policy development. They submit that a longitudinal research approach, in which the focus is on tracing criminal careers, is the most powerful technique for providing information on the relationship between mental illness and criminality that is relevant to interpretation at the individual, as opposed to group, level.

Rabkin, J.G. (1979). Criminal behaviour of discharged mental patients: A critical appraisal of the research. Psychological Bulletin, 86(1), 1-27.

Negative community attitudes and fears are identified as a persistent obstacle to the fulfilment of community-based treatment goals. The major sources of community opposition are beliefs that the mentally ill are unpredictable and dangerous. Literature dealing with arrests among formerly hospitalized patients is reviewed with an emphasis on large prospective studies. Because mentally disturbed persons are treated differently by the criminal justice system than are other defendants, retrospective studies are not effective in answering these questions. Rabkin points out that arrests and convictions underestimate the degree of crime committed by persons and, therefore, also underestimate the frequency of violence. Another source of error noted is that mentally ill persons may be diverted out of the criminal justice system (hospitalized or acquitted on the grounds of insanity) even though they have committed a crime. Further, the charge may be reduced to a lesser offense. Thus, there may be a lowering of the overall arrest rates among mentally ill as well as a reduction in their severity, particularly for non-substance abusers. Police contacts eliminate some of these difficulties but still do underestimate the magnitude of criminal activity. Another important methodological issue is the non-equivalence of mental patient samples and the general population with respect to social and demographic factors: few studies compare patient groups to their socio-demographic peers. Given these methodological considerations, and based on the information available, Rabkin concludes that discharged mental patients are not significantly less likely than others to exhibit dangerous or illegal behaviour, but that there is no evidence to indicate that their mental status per se raises their risk.

Schellenberg, E.G., Wasylenki, D., Webster, C.D. and Goering, P. (1992). A review of arrests among psychiatric patients. International Journal of Law and Psychiatry, 15, 251-264.

On the basis of a review of articles dealing  with arrests among psychiatric patients since 1980, the authors conclude that research to date shows that between one-third to one-half of psychiatric patients have been arrested at some point. The authors explain that findings of high percentages of patients with prior arrests do not tell us about the nature of the arrests. Moreover, the authors state that arrest rates may be over or underestimated. It is possible that arrests are used by authorities to place psychiatric patients in treatment. If this is the case, then patients may be arrested for crimes that are often overlooked when committed by the general public. Thus the percentage of patients that have been arrested may be somewhat inflated. On the other hand, it is likely that mental illness often prevents arrests. Therefore, the percentage of patients who are arrested may underestimate, to a greater extent than with the general population, the percentage of patients who could actually have been arrested. Regarding the post-admission arrest findings, data have shown that approximately 1 out of every 13 patients per year experience an arrest after admission to psychiatric treatment. Less than one-fifth will be for violent crimes.

The authors review a number of factors and report that certain factors which predict arrests in the general population are also predictive of arrests for psychiatric patients. Patients with prior arrests, younger patients, male patients, non-white patients and those who are homeless are more likely to be arrested than other patients. In regards to diagnosis, the evidence suggests that substance abusers are more likely to be arrested than other patients.

Shah, A.K., Fineberg, N.A. and James, D.V. (1991). Violence among psychiatric inpatients. Acta Psychiatrica Scandanavica, 84, 305-309.

These authors review the literature dealing with violence among psychiatric inpatients and discuss possible associations and methodological flaws. The first issue raised is the lack of a common definition of violence, making comparisons across studies difficult. For example, various conceptions of violence are used by researchers, including verbal abuse or threatening behaviour, self-harm, and serious violence perpetrated toward others. This is further complicated by the use of differing populations and different data collection methods. With respect to the former, patients have been studied in a wide range of settings including inner cities, semi-rural areas, large asylums, small units, forensic units, institutions for the mentally handicapped, and psychogeriatric units. With respect to differing data collection methods, data have been collected using incident forms, routine ward documentation, and specially designed scales. Many studies have not included a comparison group, making it difficult to know whether observed levels of violence are higher or lower than might be expected.

In spite of these difficulties, however, the  authors suggest that is is possible to draw a number of provisional conclusions. Younger patients seem to be more violent than older patients. Violence prior to admission is associated with violence after admission, and patients diagnosed with schizophrenia, especially those experiencing disorganized thinking or delusions, are more likely to be violent during their admission. Depression appears to be negatively associated with violence to others. Among psychogeriatric patients, violence is associated with males, increasing age, increasing length of stay, a diagnosis of dementia, severity of cognitive impairment, and temporal lobe atrophy. Among mentally handicapped patients, violence has been associated with abnormal electroencephalograms. With respect to ward variables, violence is more common on acute psychiatric units, and occurs most often during the morning. Less violence occurs on weekends or at night. Patient overcrowding or lack of trained staff may provoke violence.

Siever, L. and Trestman, RL. (1993). The serotonin system and aggressive personality disorder. International Clinical Psychopharmacology, 8(Suppl), 2, 33-39.

The authors review the evidence implicating an association between specific pathological behavioural patterns and specific neurotransmitter dysfunction. They conclude that serotonin may be implicated in impulsivity and aggression (e.g., planned aggression), while noradrenaline may be implicated in impulsivity and environmental reactivity (e.g., fight or flight response). Both neurotransmitters would be implicated in depressive illness. More specifically, the authors review the evidence provided by studies on prolactin response to fenfluramine among patients with major depression (30) and with personality disorder (20), especially borderline personality disorders. Both groups of patients demonstrated a blunted response when compared to healthy control groups. Blunting of the response was more pronounced among suicide attempters. These studies indicate that impulsivity and aggressivity are strongly and inversely correlated with prolactin response to fenfluramine, and that serotonergic dysfunction is important in borderline personality disorders. According to these authors, these findings have major implications for drug development, specifically in relation to serotonin reuptake inhibitors in alleviating impulsive and aggressive behaviours in some personality disordered patients.

Steadman, H.J. (1981). Critically reassessing the accuracy of public perceptions of the dangerousness of the mentally ill. Journal of Health and Social Behaviour, 22, 310-316.

Steadman makes the argument that recent research on contemporary populations of ex-mental patients support public fears of the dangerousness of the mentally ill. Public attitudes are shaped largely by the disturbed behaviour of persons, usually reported in the press, who have been previously defined as mentally ill, rather than by  contact with ex-mental patients themselves. The question arises as to how the behaviours that are actually exhibited by ex-mental patients or the mentally ill in general compare with those depicted in media dramatizations. The popular answer among health professionals has been that there is a huge discrepancy. But recent data on arrest rates of ex-mental patients suggest that the gap may be closing. Early studies, conducted between 1922 and 1954, that examined arrest rates of ex-mental patients following their release from hospital, consistently showed lower rates of arrest than the general population. More recent evidence has shown a higher arrest rate among ex-mental patients, particularly those that have had arrests prior to their hospitalization. Also, recent studies show that the proportion of persons in mental hospital populations with previous arrest records is growing and this may be one explanation for the more recent findings of an increased criminality among ex-mental patients. While this is certainly a mitigating factor in understanding the relationship between mental illness and criminality, the public views anyone released from a mental hospital as a potential criminal and will make few allowances for prior criminality.

A second explanation for the apparent growing criminality of ex-mental patients may be that, prior to deinstitutionalization, these individuals were detained in hospital during the time period when they were at greatest risk of committing crimes. This explanation is supported by data showing the average age of discharged mental patients has decreased to below 40 years of age—the time when criminal activity is highest. Ex-mental patients may be more likely to be arrested than those who have no history of psychiatric hospitalization and this may inflate the incidence of their criminal behaviour. However, this is unlikely to explain three-fold differences in arrest rates between ex-mental patients and the general population. Steadman concludes by indicating that it no longer seems defensible to assure community associations that ex-mental patients are less dangerous, statistically, than their neighbours. Given their higher statistical propensity for criminality, they do carry certain risks to the community, and, therefore, the public is justified in its fear. In order to improve this situation, core beliefs about unpredictability of the mentally ill, particularly unpredictability of dangerousness, must be addressed directly. Mental health professionals need to recognize the extent to which ex-mental patients may threaten public safety, and expose the public to more direct (rather than indirect) contact with the mentally ill.

Teplin, L.A. (1983). The criminalization of the mentally ill: Speculation in search of data. Psychological Bulletin, 94(1), 54-67.

Teplin provides an excellent critical appraisal of the arguments supporting the view that mentally disordered persons are being criminalized and notes that  empirical evidence bearing on this question is problematic. Of specific interest is Teplin’s observation that studies comparing the arrest rates of former mental patients with those of the general population, although designed to assess the relative dangerousness of ex-mental patients, are also applicable to the criminalization issue. More specifically, she argues that one would expect higher arrest rates among mentally disordered persons compared to non-disordered persons if the mentally ill were being criminalized. The relationship would be a result of administrative and programmatic factors in the handling of mentally disordered persons, rather than etiological factors. However, Teplin argues that the apparently high arrest rates found among previously hospitalized mental patients can be explained by the high proportion of persons with criminal records now present in psychiatric hospitals. Former mental patients without criminal records have arrest rates comparable to those of the general population. Further, the evidence regarding the extent to which mentally disordered persons with no prior hospitalization are being processed through criminal justice systems, is inconclusive.

Teplin also underscores the importance of understanding the use of police discretion in their handling of the mentally ill. Although evidence has been mixed, she suggests that police do process mentally ill individuals through the criminal justice system. Studies examining the prevalence of mental illness in jails have been plagued with methodological problems so have not provided convincing proof to support the criminalization hypothesis. She concludes that the available empirical evidence provides only tentative support for the criminalization hypothesis.

Torrey, E.F. (1994). Violent behaviour by individuals with serious mental illness. Hospital and Community Psychiatry, 45, 653-662.

Torrey reviews both scientific studies and selected media stories bearing on the relationship of mental illness and violence. Scientific studies are grouped according to five categories: (1) persons who have been arrested; (2) psychiatric inpatients; (3) psychiatric outpatients; (4) families with a member who has a serious mental illness; and (5) individuals identified as having serious mental illness by surveys of the general population. Prior to deinstitutionalization, studies of individuals who have been arrested showed lower arrest rates than the general population. Studies since deinstitutionalization have yielded higher arrest rates for the mentally ill than for the general population. Torrey cautions that arrest rates alone are not a reasonable measure of violence because the majority of arrests are for non-violent crimes and this may be especially true for individuals with mental illness who may be “criminalized” for misdemeanours relating to disorderly conduct. Because violent acts are a major selection criteria for psychiatric hospitalization, studies of psychiatric inpatients while in hospital are very problematic. Studies of patients post-release may  underestimate violence because only those patients who are expected to be non-violent will be released. Studies of psychiatric outpatients have indicated that a higher risk of violence is associated with psychotic symptoms.

In addition, Torrey reports that families of mentally ill may be at higher risk of violence. The National Alliance for the Mentally Ill studied this issue in 1990. The study found that for families in which a member has a serious mental illness, 10.6% of these persons had physically harmed another person, and another 12.2% had threatened to harm another person.

Torrey indicates that cross-sectional surveys of the general population show a relationship between violence and mental disorder. He suggests that although the vast majority of the mentally ill are no more violent than the general population, there does exist a sub-group of the mentally ill which is more violent. For those with serious mental illness, a prior history of violence and a concurrent substance abuse disorder, and non-compliance with medication are factors that appear to increase the risk. In response to these findings, Torrey recommends a number of restrictive measures that: the criteria for involuntary confinement should incorporate these predictors of violence; the right to involuntarily medicate a patient should be automatically included with the right to involuntarily hospitalize a patient; outpatient commitment should be considered for community treatment and supervision; and persons with a history of violence should not be released into the community. Torrey also states that mechanisms should be developed to monitor compliance with oral medication while in the community.

Whitmer, G.E. (1980). From hospitals to jails: The fate of California’s deinstitutionalized mentally ill. American Journal of Orthopsychiatry, 50(1), 65-75.

This now-classic paper describes the consequences of mental health reforms that shifted the locus of treatment from institutional to community settings. The major thesis of the paper is that the California Lanterman, Petris, Short Act of 1968 (the first act to change the standard for involuntary confinement to one of dangerousness) resulted in the “criminalization of the mentally ill”. Whitmer describes the process by which mentally ill persons come to court on criminal charges for crimes that are symptomatic of their illness. He describes a confluence of program factors (inadequate or ineffective community care), clinical factors (reluctance to engage in treatment, non-compliance, treatment resistance), and legal factors (dangerousness standard) that have resulted in many of the mentally ill falling through the cracks in the mental health system and ending up in the criminal justice system. He describes these patients as having been forfeitured by the mental health system.

Appendix B: Glossary of Terms

The following glossary of terms is offered to assist readers in understanding the scientific and technical language used  throughout this document. Unless otherwise referenced, definitions are drawn from Last, J.M. (1988). A Dictionary of epidemiology (2nd edition). Toronto: Oxford University Press, and Rothman, K.J. (1986). Modern epidemiology. Boston: Little, Brown and Company.

Bias is used to refer to an error in study design, data collection, or interpretation that can lead to faulty conclusions. Bias may be a result of misclassification of study subjects on either exposure or outcome factors, or it may result from studying selected groups of individuals such as mental patients or incarcerated offenders. Confounding (described below) is a third source of bias that must be controlled in order to make causal inferences.

Case-control studies choose study subjects on the basis of the outcome of interest (e.g. violent versus non-violent) and then survey subjects for exposure information (e.g. history of mental illness). Temporal ordering of factors may be a problem for case-control studies because investigators must rely on subject’s memory for exposure information. Also, there is the possibility that cases (those who are violent) will remember past events differently than controls, leading to recall bias. As a result, causal inferences are usually not made on the basis of case-control studies without supporting evidence from cohort investigations.

Cohort Studies follow two or more groups through time who differ with respect to some purported causal factor (termed the “exposure”). The groups are compared with respect to their outcomes. An essential element of the cohort study is that all groups are free from the outcome of interest (in this case violence) at the outset of the study. Cohort studies make it possible to establish the temporal ordering of study factors, something that is crucial in making causal interpretations. Therefore, they are considered to provide the strongest evidence supporting causal interpretations.

Confounding occurs when the effects of two or more factors become mixed in a dataset such that it is difficult to see their independent effects. Confounding factors are related to the outcome of study. If they are also differentially distributed across the study groups, they can distort study results. Statistical adjustment may reduce or control the effects of confounding. Factors that may confound the relationship between mental illness and violence include age, sex, and past history of violence.

Cross-sectional surveys collect exposure (e.g. mental illness) and outcome (e.g. violence) simultaneously on a representative sample of persons. Thus, it is impossible to temporally order factors. Cross-sectional studies are considered to be ideal for generating hypothesis but are never used as the basis for inferring causality.

DSM Nosology, (published by the American Psychiatric Association) has been the accepted standard for  psychiatric diagnoses in North America for many decades. The most recent version is DSM-IV (published in 1994). However, most studies reported in the literature use DSM-III (Revised version). The DSM involves assessment on five axes, each of which refers to a different domain of information. Axis I refers to clinical disorders and other conditions that may be a focus of clinical attention. Axis II refers to personality disorders and mental retardation. Axis III is used to code medical conditions. Axis IV describes psychosocial stressors and environmental problems, and Axis V is used to make a global assessment of the patient’s social and occupational functioning.

Epidemiology studies the occurrence of diseases and health events in human populations and their relationship with co-occurring “risk” and “protective” factors in order to derive causal explanations that can be used to lessen the burden of illness on the population. In the United States of America, courts of law have determined that statements of causality in human populations come most authoritatively from studies employing the causal logic characteristic of epidemiologic studies.

Selection bias is an error due to systematic differences in the characteristics between those who are selected for study (e.g. mental patients or incarcerated offenders) and the population from which they are drawn (all mentally ill or all persons who are violent).

Statistical adjustment is used to reduce differences in composition of two groups so that they may be fairly compared with respect to an outcome of interest. Unadjusted comparisons may result in biased conclusions.