Homicide in discharged patients with schizophrenia and other psychoses: a national case-control study.

OBJECTIVE: To investigate factors associated with homicide after discharge from hospital in patients with schizophrenia and other psychoses.
DESIGN: All homicides committed by patients with psychosis within 6 months of hospital discharge were identified in Sweden from 1988-2001 and compared with patients with psychoses discharged over the same time period who did not subsequently commit any violent offences. Medical records were then collected, and data extracted using a validated protocol. Interrater reliability tests were performed on a subsample, and variables with poor reliability excluded from subsequent analyses.
RESULTS: We identified 47 cases who committed a homicide within 6 months of discharge, and 105 controls who did not commit any violent offence after discharge. On univariate analyses, clinical factors on admission associated with homicide included evidence of poor self-care, substance misuse, and being previously hospitalized for a violent episode. Inpatient characteristics included having a severe mental illness for one year prior to admission. After-care factors associated with homicide were evidence of medication non-compliance and substance misuse. The predictive validity of combining two or three of these factors was not high. Depression appeared to be inversely associated with homicide, and there was no relationship with the presence of delusions or hallucinations.
CONCLUSIONS: There are a number of potentially treatable factors that are associated with homicide in schizophrenia and other psychoses. Associations with substance misuse and treatment compliance could be the focus of therapeutic interventions if validated in other samples. However, their clinical utility in violence risk assessment remains uncertain.