A novel approach to determining violence risk in schizophrenia: developing a stepped strategy in 13,806 discharged patients

Clinical guidelines recommend that violence risk be assessed in schizophrenia. Current approaches are resource-intensive as they employ detailed clinical assessments of dangerousness for most patients. An alternative approach would be to first screen out patients at very low risk of future violence prior to more costly and time-consuming assessments. In order to implement such a stepped strategy, we developed a simple tool to screen out individuals with schizophrenia at very low risk of violent offending. We merged high quality Swedish national registers containing information on psychiatric diagnoses, socio-demographic factors, and violent crime. A cohort of 13,806 individuals with hospital discharge diagnoses of schizophrenia was identified and followed for up to 33 years for violent crime. Cox regression was used to determine risk factors for violent crime and construct the screening tool, the predictive validity of which was measured using four outcome statistics. The instrument was calibrated on 6,903 participants and cross-validated using three independent replication samples of 2,301 participants each. Regression analyses resulted in a tool composed of five items: male sex, previous criminal conviction, young age at assessment, comorbid alcohol abuse, and comorbid drug abuse. At 5 years after discharge, the instrument had a negative predictive value of 0.99 (95% CI = 0.98–0.99), meaning that very few individuals who the tool screened out (n = 2,359 out of original sample of 6,903) were subsequently convicted of a violent offence. Screening out patients who are at very low risk of violence prior to more detailed clinical assessment may assist the risk assessment process in schizophrenia.     

Schizophrenia and Violence: Systematic Review and Meta-Analysis

Background

Although expert opinion has asserted that there is an increased risk of violence in individuals with schizophrenia and other psychoses, there is substantial heterogeneity between studies reporting risk of violence, and uncertainty over the causes of this heterogeneity. We undertook a systematic review of studies that report on associations between violence and schizophrenia and other psychoses. In addition, we conducted a systematic review of investigations that reported on risk of homicide in individuals with schizophrenia and other psychoses.

Methods and Findings

Bibliographic databases and reference lists were searched from 1970 to February 2009 for studies that reported on risks of interpersonal violence and/or violent criminality in individuals with schizophrenia and other psychoses compared with general population samples. These data were meta-analysed and odds ratios (ORs) were pooled using random-effects models. Ten demographic and clinical variables were extracted from each study to test for any observed heterogeneity in the risk estimates. We identified 20 individual studies reporting data from 18,423 individuals with schizophrenia and other psychoses. In men, ORs for the comparison of violence in those with schizophrenia and other psychoses with those without mental disorders varied from 1 to 7 with substantial heterogeneity (I ² = 86%). In women, ORs ranged from 4 to 29 with substantial heterogeneity (I ² = 85%). The effect of comorbid substance abuse was marked with the random-effects ORs of 2.1 (95% confidence interval [CI] 1.7–2.7) without comorbidity, and an OR of 8.9 (95% CI 5.4–14.7) with comorbidity (p<0.001 on metaregression). Risk estimates of violence in individuals with substance abuse (but without psychosis) were similar to those in individuals with psychosis with substance abuse comorbidity, and higher than all studies with psychosis irrespective of comorbidity. Choice of outcome measure, whether the sample was diagnosed with schizophrenia or with nonschizophrenic psychoses, study location, or study period were not significantly associated with risk estimates on subgroup or metaregression analysis. Further research is necessary to establish whether longitudinal designs were associated with lower risk estimates. The risk for homicide was increased in individuals with psychosis (with and without comorbid substance abuse) compared with general population controls (random-effects OR = 19.5, 95% CI 14.7–25.8).

Conclusions

Schizophrenia and other psychoses are associated with violence and violent offending, particularly homicide. However, most of the excess risk appears to be mediated by substance abuse comorbidity. The risk in these patients with comorbidity is similar to that for substance abuse without psychosis. Public health strategies for violence reduction could consider focusing on the primary and secondary prevention of substance abuse. Please see later in the article for Editors'' Summary     

Elevated temperature may intensify the positive effects of nutrients on microbial decomposition in streams

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