Most psychiatric disorders - including depression -- do not predict future violent behavior, according to a longitudinal study of delinquent youth. Some delinquent youth with current psychiatric illness may also be violent - males with mania were more than twice as likely to report current violence than those without - but those relationships are not necessarily causal.
The one exception is when there is substance abuse and dependence. That was a predictor of violence in people with psychiatric conditions.
The study used data from the Northwestern Juvenile Project, a longitudinal study of youth who were detained at the Cook County Juvenile Temporary Detention Center in Chicago between 1995 and 1998. Violence and psychiatric disorders were assessed via self-report in 1,659 youth aged 13 to 25 years interviewed up to four times between three and five years after detention.
"Our findings are relevant to the recent tragic plane crash in the French Alps. Our findings show that no one could have predicted that the pilot - who apparently suffered from depression - - would perpetrate this violent act," said corresponding author Linda Teplin, the Owen L. Coon Professor of Psychiatry and Behavioral Sciences at Northwestern University Feinberg School of Medicine. "It is not merely a suicide, but an act of mass homicide."
Published in the Journal of the American Academy of Child&Adolescent Psychiatry. Other Northwestern authors include Karen M. Abram, Jessica A. Jakubowski, Mina K. Dulcan and Leah J. Welty. This work was supported by National Institute on Drug Abuse grants R01DA019380, R01DA022953, and R01DA028763; National Institute of Mental Health grants R01MH54197 and R01MH59463 of the National Institutes of Health and grants 1999-JE-FX-1001, 2005-JL-FX-0288, and 2008-JF-FX- 0068 from the Office of Juvenile Justice and Delinquency Prevention.