Controlling for both genetic and environmental risks from parental substance dependence, parental separation was associated with early initiation across substance classes, with effects of separation most pronounced through ages 10 or 13. Controlling for parental separation only, a slight reduction in risks from parental substance dependence was observed, suggesting partial mediation at best. A greater reduction was observed with additional adjustment for demographic characteristics, coparent substance use/dependence, and psychiatric comorbidities of both parents and offspring. In most models, having a substance dependent parent was no longer predictive, except for onset of smoking as a function of parental cannabis dependence, described above. In contrast, effects of parental separation remained strong, suggesting parental separation confers unique risks beyond demographic, familial and individual-level influences highly correlated with parental substance dependence.
