Age of cannabis use onset and adult drug abuse symptoms : a prospective study of common risk factors and indirect effects

Abstract

Objective: The present study examined (1) whether the associations between cannabis use (CU) age of onset and drug abuse by 28 years remain when controlling for risk factors in childhood, adolescence and early adulthood; and (2) developmental pathways from early risk factors to drug abuse problems. Method: Participants from a longitudinal sample of low SES boys (N=1030) were followed from 6 to 28 years. Self-reported CU onset between 13 and 17 years of age and drug abuse symptoms by 28 years were examined. Results: The odds of developing any drug abuse symptoms by 28 years were reduced by 31% for each year of delayed CU onset (OR = 0.69). Cannabis, alcohol and other drug frequency at 17 years mediated this association. Still, even when taking that frequency of use into account, adolescents who started using cannabis before 15 years were at higher risk of developing drug abuse symptoms by age 28. Significant indirect effects were found from early adolescent delinquency and affiliation with deviant friends to drug abuse symptoms at 28 years through CU age of onset and substance use frequency at 17 years. Conclusions: Results suggest more clearly than before that prevention programs should aim at delaying CU onset in order to prevent or reduce drug abuse in adulthood. Furthermore, prevention programs targeting delinquency and/or affiliation with deviant friends in childhood or early adolescence could indirectly reduce substance abuse in adulthood without addressing substance use specifically.