models (e.g. moderation of association between P3 amplitude and externalizing behavior by the EXT PGS) can be tested. PGS are by nature imprecise as they are an aggregation of variants that are associated with specific behaviors or diagnoses and contain noise that can obscure the EXT PGS association with relevant measures in other domains, including P3 amplitude. In addition, the EXT PGS was derived from a multivariate GWAS that only included EA individuals, and the predictive performance of EA-derived PGS is lower in non-EA samples (Duncan et al., 2019). Lastly, environmental variables play a critical role in the development and expression of externalizing behaviors and future work should incorporate environmental covariates (e.g. education, parenting style) as they may buffer the associations between the EXT PGS, P3 amplitude, and externalizing behavior.
