Abstract
Children who enter foster care are at unique risk for developing substance abuse due to experiencing early life stressors. A large body of research has revealed robust effects of various stressors on later substance use, implicating the role of early neurobiological changes that create chronic internalizing problems. However, less literature has investigated externalizing behavior as a mechanism underlying this relationship. Moreover, few studies have examined these mechanisms through a model of cumulative risk. The present study examined whether the prospective association between cumulative pre-adoptive risk (e.g., maltreatment, age at placement, foster placement instability, ever having lived with birth parent) and adolescent/young-adult substance use was mediated by childhood internalizing and externalizing problems in youth adopted from foster care. Participants included 82 adoptees, most with histories of prenatal substance exposure (72%). We tested parent-rated internalizing and externalizing problems across 5 years in childhood as simultaneous mediators of cumulative risk and level of substance use 11–15 years later. Bootstrapping mediation procedures, controlling for age, prenatal substance exposure, adolescent/young adult mental health symptomatology, and youth participation in follow-up, revealed a significant indirect effect of cumulative risk on substance use through childhood internalizing problems, but not externalizing problems. These results underline the importance of mitigating early risk for children in the child welfare system and call for targeting childhood emotion dysregulation to reduce likelihood of substance abuse among previously high-risk adoptees. Nevertheless, low rates of substance use overall in the present sample underscore the positive impact of adoptive placement on mitigating risk for substance abuse among foster youth.