Improving risk assessment in schizophrenia: epidemiological investigation of criminal history factors.

BACKGROUND: Violence risk assessment in schizophrenia relies heavily on criminal history factors.

AIMS: To investigate which criminal history factors are most strongly associated with violent crime in schizophrenia.

METHOD: A total of 13 806 individuals (8891 men and 4915 women) with two or more hospital admissions for schizophrenia were followed up for violent convictions. Multivariate hazard ratios for 15 criminal history factors included in different risk assessment tools were calculated. The incremental predictive validity of these factors was estimated using tests of discrimination, calibration and reclassification.

RESULTS: Over a mean follow-up of 12.0 years, 17.3% of men (n = 1535) and 5.7% of women (n = 281) were convicted of a violent offence. Criminal history factors most strongly associated with subsequent violence for both men and women were a previous conviction for a violent offence; for assault, illegal threats and/or intimidation; and imprisonment. However, only a previous conviction for a violent offence was associated with incremental predictive validity in both genders following adjustment for young age and comorbid substance use disorder.

CONCLUSIONS: Clinical and actuarial approaches to assess violence risk can be improved if included risk factors are tested using multiple measures of performance.