Marijuana use and psychiatric illness: a follow-up study.

In 1970, 100 regular marijuana users and 50 of their nonuser friends underwent a psychiatric evaluation. Of these, 97 users and all 50 nonusers were reinterviewed 6-7 years later. At follow-up, 60% of both groups had a psychiatric diagnosis. Antisocial personality was more prevalent in users; otherwise, there were no significant differences in diagnosis. Depression, alcohol abuse, and antisocial personality increased in users. However, these increases occurred in subjects who had reported problems in these areas in the initial interview but did not then meet diagnostic criteria. There was not a significant increase in the total number with a diagnosable illness.