Context: The relationship between mental illness and violence has a significant effect on mental health policy, clinical practice, and public opinion about the dangerousness of people with psychiatric disorders.
Objective: To use a longitudinal data set representative of the US population to clarify whether or how severe mental illnesses such as schizophrenia, bipolar disorder, and major depression lead to violent behavior.
Design: Data on mental disorder and violence were collected as part of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a 2-wave face-to-face survey conducted by the National Institute on Alcohol Abuse and Alcoholism.
Participants: A total of 34 653 subjects completed NESARC waves 1 (2001-2003) and 2 (2004-2005) interviews. Wave 1 data on severe mental illness and risk factors were analyzed to predict wave 2 data on violent behavior.
Main outcome measures: Reported violent acts committed between waves 1 and 2.
Results: Bivariate analyses showed that the incidence of violence was higher for people with severe mental illness, but only significantly so for those with co-occurring substance abuse and/or dependence. Multivariate analyses revealed that severe mental illness alone did not predict future violence; it was associated instead with historical (past violence, juvenile detention, physical abuse, parental arrest record), clinical (substance abuse, perceived threats), dispositional (age, sex, income), and contextual (recent divorce, unemployment, victimization) factors. Most of these factors were endorsed more often by subjects with severe mental illness.
Conclusions: Because severe mental illness did not independently predict future violent behavior, these findings challenge perceptions that mental illness is a leading cause of violence in the general population. Still, people with mental illness did report violence more often, largely because they showed other factors associated with violence. Consequently, understanding the link between violent acts and mental disorder requires consideration of its association with other variables such as substance abuse, environmental stressors, and history of violence.