UC San Diego

Objective: The purpose of this study is to assess whether childhood externalizing and internalizing behaviors predict substance use initiation during adolescence. Additionally, we examined whether there was effect measure modification by sex of the child on this association. Methods: This study is a secondary analysis using data from a prospective cohort study, the Fragile Families and Child Wellbeing Study. A multivariable log link regression analysis was used to estimate the risk of initiation of marijuana, cigarettes, and alcohol at age 15, based on internalizing and externalizing behaviors measured at age 9. Models were adjusted for child race/ethnicity, maternal age, maternal substance use during pregnancy, poverty level, and ACEs. Results: Out of 2935 children at age 9, 6.5% met the criteria for high externalizing score, and 3.6% met the criteria for high internalizing score. High externalizing score was a risk factor for marijuana (ARR= 1.57, CI= 1.10, 2.20) and cigarette use (ARR= 2.38, CI= 1.31, 4.17) initiation. High internalizing score decreased the risk of alcohol use initiation, after controlling for all confounding variables. There was no evidence of effect modification by child sex. Conclusion: These findings are of public health importance, as they add to the paucity of information on known risk factors for substance use initiation among adolescents. Additionally, these results can be used to help identify youth who may benefit from interventions designed to prevent adolescent substance use initiation.