Our results should be interpreted within the context of the following limitations. First, COGA is a high-risk sample, with individuals from extended families enriched for alcohol use disorders. Findings may not be generalizable to other samples recruited and ascertained with different risk profiles. Second, measures of parenting/parent-child relationship were reported from the adolescent’s perspective. It is possible that adolescents’ externalizing behavior or their genotype impacted their perception of parent-child relationship characteristics (Kendler & Baker, 2007), and these parenting measures may not objectively reflect parental behavior. Capturing parenting as a multidimensional construct with multi-informant data is an important next step. Third, assessments of parental externalizing disorders occurred years prior to the adolescent interview. Thus, they represent parents’ lifetime assessments of externalizing psychopathology, rather than externalizing behavior measured contemporaneously with adolescent reports. Fourth, at present, the amount of variance accounted for by polygenic score for the externalizing phenotype remains modest. In addition, in our genetic nurturance analyses, the mediating effect via parental externalizing psychopathology was of small magnitude, though comparable to the genetic nurturance analyses for substance use phenotypes reported in Saunders
