This is the first study to examine both biologically-based variables – P3 and the EXT PGS – concurrently to determine the indirect effect of P3 amplitude on the association between EXT PGS and externalizing behaviors. Our findings suggest that both known genetic (EXT PGS) and neurophysiological (P3 amplitude) risk markers each contribute independently to the expression of externalizing behaviors. However, we do not view these findings as a definitive disconfirmation of the hypothesis that P3 amplitude mediates the association between EXT PGS and externalizing behaviors. The data used in these analyses are all cross-sectional and therefore not suited to make causal inferences. Also, issues of measurement error and small sample size need to be considered in the interpretation of these results. Therefore, future research efforts in large, longitudinal datasets should attempt to further test any theoretical mediation models and analyses should be replicated as more powerful measures of genetic risk become available.
