We used genome-wide SNP data to examine how polygenic predispositions for adulthood externalizing disorders manifest in earlier developmental stages and whether key environmental factors moderate genetic influences to predict externalizing disorders. We found a modestly sized effect whereby genetic predispositions toward externalizing disorders in adulthood also manifest as clinical-level problems at younger ages. Identifying whether the small effect size reflects a modest genetic correlation between adolescent and adult externalizing disorders or is attributable to the fact that GWAS-derived polygenic scores only account for common (versus rare; Gibson, 2012) genetic variation is an important direction for future research. It is especially impressive that polygenic scores predicted adolescents' and young adults' externalizing disorder composite even after accounting for parental externalizing disorder history. We also found that genetic predispositions for adult externalizing disorders predicted subclinical externalizing behavior and multiple facets of impulsivity in adolescents and young adults. This nicely maps onto evidence from twin studies that a highly heritable behavioral disinhibition factor broadly predisposes individuals to a range of externalizing disorders (Kendler et al., 2003; Krueger et al., 2002). The differential age associations
