Mental disorders and violence in a total birth cohort - Results from the Dunedin study

Background: We report on mental disorders and violence for a birth cohort o f young adults, regardless of their contact with the health or justice syst ems. Methods: We studied 961 young adults who constituted 94% of a total-city bi rth cohort in New Zealand, April 1, 1972, through March 31, 1973. Past-year prevalence of mental disorders was measured using standardized DSM-III-R i nterviews. Past-year violence was measured using self-reports of criminal o ffending and a search of official conviction records. We also tested whethe r substance use before the violent offense, adolescent excessive perception s of threat, and a juvenile history of conduct disorder accounted for the l ink between mental disorders and violence. Results: Individuals meeting diagnostic criteria for alcohol dependence, ma rijuana dependence, and schizophrenia-spectrum disorder were 1.9 (95% confi dence interval [CI], 1.0-3.5),3.8 (95% CI, 2.2-6.8), and 2.5 (95% CI, 1.1-5 .7) times, respectively, more likely than control subjects to be violent. P ersons with at least 1 of these 3 disorders constituted one fifth of the sa mple, but they accounted for half of the sample's violent crimes (10% of vi olence risk was uniquely attributable to schizophrenia-spectrum disorder). Among alcohol-dependent individuals, violence was best explained by substan ce use before the offense; among marijuana-dependent individuals, by a juve nile history of conduct disorder; and among individuals with schizophrenia- spectrum disorder, by excessive perceptions of threat and a history of cond uct disorder. Conclusions: In the age group committing most violent incidents, individual s with mental disorders account for a considerable amount of violence in th e community. Different mental disorders are linked to violence via differen t core explanations, suggesting multiple-targeted prevention strategies.