The epidemiology of mentally disordered offending: a systematic review of studies, based in the general population, of criminality combined with psychiatric illness.

BACKGROUND: The international literature, from 1990 onwards, on the epidemiology of mentally disordered offending (MDO) was systematically reviewed. Studies based solely in the general population are reported in this article. METHODS: Database searches were made back to 1990, followed by citation tracing with the authors or major publications. RESULTS: Two cross-sectional surveys and seven cohort studies were found that have given rise to epidemiological data about MDO in the general population. The most useful data come from cohort studies in Scandinavia. In Scandinavia, the prevalence of MDO up to age 26-30 years is 2.1-2.8 per 100 for men and about half this amount for women. Conduct problems in childhood and deprivation seem to be predictors of future MDO. Mental disorder is associated with acts of crime, most particularly acts of a violent nature. CONCLUSIONS: No systematic epidemiological study of MDO in its own right was found. Those studies which provide data on MDO generally make poor use of statistical methodology. Professional epidemiological and statistical input is required to fully exploit existing data and adequately plan future studies of MDO.