Figure 1.

Adoption design and model predictions. Parent smoking is assumed to affect offspring functioning through both an environmentally mediated specific pathway, which results in an increased risk of adolescent smoking, and a genetically-mediated general pathway, which results in a non-specific increased risk of disinhibited behavior. In non-adoptive families, parent smoking is predicted to be associated with a wide range of offspring outcomes because both pathways are operative. Alternatively, in adoptive families parent smoking is predicted to be associated specifically with offspring smoking because only the environmentally mediated pathway is operative.