Mental Illness and Violence: Proof or Stereotype?

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Appendix A: Annotated Bibliography cont'd

Studies of Psychiatric Patients cont'd

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.

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