Serious criminal offending and mental disorder. Case linkage study.

BACKGROUND: A relationship exists between mental disorder and offending behaviours but the nature and extent of the association remains in doubt.

METHOD: Those convicted in the higher courts of Victoria between 1993 and 1995 had their psychiatric history explored by case linkage to a register listing virtually all contacts with the public psychiatric services.

RESULTS: Prior psychiatric contact was found in 25% of offenders, but the personality disorder and substance misuse accounted for much of this relationship. Schizophrenia and affective disorders were also over-represented, particularly those with coexisting substance misuse.

CONCLUSIONS: The increased offending in schizophrenia and affective illness is modest and may often be mediated by coexisting substance misuse. The risk of a serious crime being committed by someone with a major mental illness is small and does not justify subjecting them, as a group, to either increased institutional containment or greater coercion.