Childhood conduct disorder trajectories, prior risk factors and cannabis use at age 16: birth cohort study

AIMS To investigate the prevalence of cannabis use and problem use in boys and girls at age 16 years, and to investigate the role of adversity in early life and of conduct disorder between the ages of 4 and 13 years as risk factors for these outcomes. DESIGN Birth cohort study. SETTING England. PARTICIPANTS A total of 4159 (2393 girls) participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort providing information on cannabis use at age 16. MEASUREMENTS Cannabis use and problem cannabis use at age 16 were assessed by postal questionnaire. Material adversity, maternal substance use, maternal mental health and child conduct disorder were all assessed by maternal report. FINDINGS Cannabis use was more common among girls than boys (21.4% versus 18.3%, P = 0.005). Problem cannabis use was more common in boys than girls (3.6% versus 2.8%, P = 0.007). Early-onset persistent conduct problems were associated strongly with problem cannabis use [odds ratio (OR) = 6.46, 95% confidence interval (CI) = 4.06-10.28]. Residence in subsidized housing (OR = 3.10, 95% CI = 1.95, 4.92); maternal cannabis use (OR 8.84, 95% CI 5.64-13.9) and any maternal smoking in the postnatal period (OR = 2.69, 95% CI = 1.90-3.81) all predicted problem cannabis use. Attributable risks for adolescent problem cannabis use associated with the above factors were 25, 13, 17 and 24%, respectively. CONCLUSIONS Maternal smoking and cannabis use, early material disadvantage and early-onset persistent conduct problems are important risk factors for adolescent problem cannabis use. This may have implications for prevention.