Third, in European ancestry families, we found evidence consistent with our hypothesis that parental externalizing psychopathology mediated the association between parental externalizing polygenic score and adolescent externalizing behavior, after accounting for adolescent externalizing polygenic score. Family and adoption studies have shown that parental externalizing behaviors represent both genetic and environmental risk for offspring (Kendler et al., 2015; Kendler et al., 2012; Keyes et al., 2008). Using parental and adolescent polygenic scores, we built on prior evidence from latent genetic studies to show that genetic nurture effects on adolescent externalizing behavior, while relatively small in magnitude, are explained, in part, by parents’ own externalizing behavior. This demonstrates that parental externalizing represents a form of environmental risk for children. Our result suggests that environmental interventions that focus on treating externalizing related disorders in parents, and promotion of recovery, may help reduce intergenerational transmission of genetic risk for externalizing behavior.
