Seena Fazel and colleagues investigate the association between schizophrenia and other psychoses and violence and violent offending, and show that the increased risk appears to be partly mediated by substance abuse comorbidity.

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Context Persons with schizophrenia are thought to be at increased risk of committing violent crime 4 to 6 times the level of general population individuals without this disorder. However, risk estimates vary substantially across studies, and considerable uncertainty exists as to what mediates this elevated risk. Despite this uncertainty, current guidelines recommend that violence risk assessment should be conducted for all patients with schizophrenia. Objective To determine the risk of violent crime among patients diagnosed as having schizophrenia and the role of substance abuse in mediating this risk. Design, Setting, and Participants Longitudinal designs were used to link data from nationwide Swedish registers of hospital admissions and criminal convictions in 1973-2006. Risk of violent crime in patients after diagnosis of schizophrenia (n = 8003) was compared with that among general population controls (n = 80 025). Potential confounders (age, sex, income, and marital and immigrant status) and mediators (substance abuse comorbidity) were measured at baseline. To study familial confounding, we also investigated risk of violence among unaffected siblings (n = 8123) of patients with schizophrenia. Information on treatment was not available. Main Outcome Measure Violent crime (any criminal conviction for homicide, assault, robbery, arson, any sexual offense, illegal threats, or intimidation). Results In patients with schizophrenia, 1054 (13.2%) had at least 1 violent offense compared with 4276 (5.3%) of general population controls (adjusted odds ratio [OR], 2.0; 95% confidence interval [CI], 1.8-2.2). The risk was mostly confined to patients with substance abuse comorbidity (of whom 27.6% committed an offense), yielding an increased risk of violent crime among such patients (adjusted OR, 4.4; 95% CI, 3.9-5.0), whereas the risk increase was small in schizophrenia patients without substance abuse comorbidity (8.5% of whom had at least 1 violent offense; adjusted OR, 1.2; 95% CI, 1.1-1.4; P<.001 for interaction). The risk increase among those with substance abuse comorbidity was significantly less pronounced when unaffected siblings were used as controls (28.3% of those with schizophrenia had a violent offense compared with 17.9% of their unaffected siblings; adjusted OR, 1.8; 95% CI, 1.4-2.4; P<.001 for interaction), suggesting significant familial (genetic or early environmental) confounding of the association between schizophrenia and violence. Conclusions Schizophrenia was associated with an increased risk of violent crime in this longitudinal study. This association was attenuated by adjustment for substance abuse, suggesting a mediating effect. The role of risk assessment, management, and treatment in individuals with comorbidity needs further examination.

Its controversial past notwithstanding, psychopathy has emerged as one of the most important clinical constructs in the criminal justice and mental health systems. One reason for the surge in theoretical and applied interest in the disorder is the development and widespread adoption of reliable and valid methods for its measurement. The Hare PCL-R provides researchers and clinicians with a common metric for the assessment of psychopathy, and has led to a surge in replicable and meaningful findings relevant to the issue of risk for recidivism and violence, among other things. Most of the research thus far has been based on North American samples of offenders and forensic psychiatric patients. We summarize this research and compare it with findings from several other countries, including England and Sweden. We conclude that the ability of the PCL-R to predict recidivism, violence, and treatment outcome has considerable cross-cultural generalizability, and that the PCL-R and its derivatives play a major role in the understanding and prediction of crime and violence.

Objective To investigate the predictive validity of tools commonly used to assess the risk of violence, sexual, and criminal behaviour.Design Systematic review and tabular meta-analysis of replication studies following PRISMA guidelines.Data sources PsycINFO, Embase, Medline, and United States Criminal Justice Reference Service Abstracts. Review methodsWe included replication studies from 1 January 1995 to 1 January 2011 if they provided contingency data for the offending outcome that the tools were designed to predict. We calculated the diagnostic odds ratio, sensitivity, specificity, area under the curve, positive predictive value, negative predictive value, the number needed to detain to prevent one offence, as well as a novel performance indicator-the number safely discharged. We investigated potential sources of heterogeneity using metaregression and subgroup analyses.Results Risk assessments were conducted on 73 samples comprising 24 847 participants from 13 countries, of whom 5879 (23.7%) offended over an average of 49.6 months. When used to predict violent offending, risk assessment tools produced low to moderate positive predictive values (median 41%, interquartile range 27-60%) and higher negative predictive values (91%, 81-95%), and a corresponding median number needed to detain of 2 (2-4) and number safely discharged of 10 (4-18). Instruments designed to predict violent offending performed better than those aimed at predicting sexual or general crime.Conclusions Although risk assessment tools are widely used in clinical and criminal justice settings, their predictive accuracy varies depending on how they are used. They seem to identify low risk individuals with high levels of accuracy, but their use as sole determinants of detention, sentencing, and release is not supported by the current evidence. Further research is needed to examine their contribution to treatment and management.

The population impact of patients with severe mental illness on violent crime, estimated by calculating the population-attributable risk, varies by gender and age. Overall, the population-attributable risk fraction of patients was 5%, suggesting that patients with severe mental illness commit one in 20 violent crimes.

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Our results suggest that different intervention policies should be considered in different socioeconomic areas. In socioeconomically advantaged areas, it might be more fruitful to focus on individually based preventions and treatments. In socioeconomically disadvantaged areas, intervention and prevention policies might be more effective on a community level, to account for shared environmental risk factors.