Parental smoking may shape tobacco use more than cannabis behavior

In celebration of Matt McGue's career, we conducted a longitudinal extension of a simple and elegant study he supervised nearly two decades ago (Keyes et al. 2008). We examined the effects of teenage exposure to parental smoking on substance use and externalizing outcomes in an adoption study. In total, 1232 offspring from 617 families were longitudinally assessed at mean ages of 15, 18, 22, and 32 years, with 37% of offspring living with at least one smoking parent at the intake assessment. We tested the effect of this exposure on offspring tobacco and cannabis use; nicotine, alcohol, and drug dependence; and ADHD, oppositional defiant disorder, conduct disorder, and adult antisocial behavior at all available follow-up assessments. Effect sizes in adoptive offspring were generally small for all outcomes, indicating minimal environmental effects from exposure to parental smoking. In contrast, the effects of exposure were stronger across all outcomes for biological (nonadopted) offspring, though not uniformly significantly statistically stronger. The environmental risk of parental smoking appears specific to offspring tobacco use while the genetic risk is more general across externalizing outcomes, consistent with Keyes et al. (2008)'s original findings from the initial intake assessment of this cohort.