Drug use and the risk of major depressive disorder, alcohol dependence, and substance use disorders.

BACKGROUND The Children in the Community Study is a prospective longitudinal study investigating the association between early drug use (childhood, adolescence, and early 20s) and later psychiatric disorders (in the late 20s). METHODS Using data from a community-based sample of 736 adults (50% female) from upstate New York, the subjects were interviewed at the mean ages of 14, 16, 22, and 27 years. Psychiatric disorders, measured by age-appropriate versions of the University of Michigan Composite International Diagnostic Interview, and participant's drug use were assessed. RESULTS Adolescent and young adult tobacco use was significantly associated with an increased risk of alcohol dependence and substance use disorders at a mean age of 27 years, but not with new episodes of major depressive disorder. Earlier alcohol use significantly predicted later major depressive disorder, alcohol dependence, and substance use disorders in the late 20s, as did early marijuana use and other illicit drug use. Except for the effect of tobacco use on major depressive disorder, early drug use was significantly related to later psychiatric disorders, even after statistically controlling for age, sex, parental educational level, family income, and prior episodes of major depressive disorder and substance use disorders. CONCLUSIONS Our results suggest that early drug use is associated with and predicts later psychiatric disorders. Preventive implications stem from the importance of studying a range of psychiatric disorders in the context of substance use assessed over a wide age range.