Childhood conduct problems, potential snares in adolescence, and problematic substance use in Brazil

Childhood conduct problems are associated with problematic substance use in adulthood; however, little is known about what might explain these associations outside of high-income countries where the majority of research is conducted. Data were analyzed from 4599 young people from the 1993 Pelotas Birth Cohort in Brazil. The exposure was conduct problems (age 11 years). Outcomes included hazardous alcohol consumption and illicit drug use (age 22 years). Mediators included police arrest (by age 18 years), gang membership (ages 18 and 22 years), and school noncompletion (by age 22 years). We performed counterfactual mediation using the parametric g-computation formula to estimate the indirect effect via all three mediators simultaneously. After adjusting for confounders (including hyperactivity problems), conduct problems were weakly associated with police arrest (OR [95% CI] = 1.45 [0.97, 2.16]) and school noncompletion (OR [95% CI] = 1.46 [1.22, 1.74]), but not with gang membership. Police arrest and gang membership were associated with illicit drug use (OR [95% CI] = 3.84 [2.46, 5.99]; OR [95% CI] = 7.78 [4.30, 14.10], respectively) and with hazardous alcohol use (OR [95% CI] = 1.60 [1.08, 2.38]; OR [95% CI] = 1.88 [1.07, 3.30]), after adjusting for confounders (including hyperactivity and emotional problems). There was no association between school noncompletion and either outcome after confounder adjustment. There was little evidence for an indirect effect of conduct problems on hazardous alcohol use and illicit drug use via all three mediators after confounder adjustment. Findings highlight the importance of school professionals being aware of the risk for school noncompletion for those with conduct problems. Additionally, programmes designed to reduce substance use in Brazil should focus on young people involved in gangs, and in the criminal justice system.