Longitudinal study of co-occurring psychiatric disorders and substance use

To examine temporal priority in the relationship between psychiatric disorders and drug use.

Psychiatric assessments and drug use were completed at three different points in time, spanning 9 years. Structured interviews were administered to a cohort of youths and their mothers. Subjects were selected on the basis of their residence in either of two counties in upstate New York. The sample was predominantly white male and female youths, aged 1 through 10 years upon initial collection of data. Psychiatric diagnoses were assessed by a supplemented version of the Diagnostic Interview Schedule for Children Version 1, using computer algorithms designed to match DSM-III-R criteria to combine information from mothers and youths. Substance use information was obtained in the interviews.

A significant relationship was found to exist between earlier adolescent drug use and later depressive and disruptive disorders in young adulthood, controlling for earlier psychiatric disorders. Earlier psychiatric disorders did not predict changes in young adult drug use.

Implications for policy, prevention, and treatment include (1) more medical attention needs to be given to the use of legal and illegal drugs; and (2) a decrease in drug use may result in a decrease in the incidence of later psychiatric disorders.