Predicting substance use in late adolescence: results from the Ontario Child Health Study follow-up.

OBJECTIVE The purpose of this study was to evaluate the relationship between use of tobacco, alcohol, marijuana, and hard drugs (substance use) and psychiatric disorder in early adolescence and substance use in late adolescence. METHOD Adolescents included in the study were identified by means of a household sampling frame and participated in the Ontario Child Health Study in 1983 and the follow-up in 1987. There were 726 12-16-year-olds (369 boys and 357 girls) in 1983 who had complete information in 1987. Data on substance use were collected from adolescents by using a structured, self-administered questionnaire. Data on psychiatric disorder were collected in 1983 from both adolescents and their parents by using problem checklists to assess conduct disorder, attention deficit disorder, and emotional disorder. RESULTS Prior substance use in 1983 was associated strongly with subsequent use in 1987. Among the psychiatric disorders assessed in 1983, only conduct disorder made an independent contribution to predicting use of marijuana (relative odds = 3.46) and other hard drugs (relative odds = 6.82) in 1987, after prior use of these substances and coexisting attention deficit and emotional disorders were controlled. Corresponding estimates of attributable risk (the expected contribution of exposure to conduct disorder to the development of substance use) were 5.7% and 11.1%, respectively. CONCLUSIONS Although a statistically significant relationship existed between conduct disorder in early adolescence and use of marijuana and hard drugs in late adolescence, the potential is limited for preventing substance use in the general population by treating conduct disorder early on.