Reduced P300 amplitude has been identified as an important candidate endophenotype for externalizing psychopathology (Iacono et al., 2002b), including the childhood disruptive disorders, substance use disorders, and ASPD. Our recent work with ES twins has helped refine and further delineate this endophenotype. Given the possibility that alcohol use can affect adolescent brain development, an important question concerns the degree to which the reduced P300 amplitude observed in adolescents reflects the underlying genetic risk for developing substance abuse as opposed to the effects of alcohol misuse. In Perlman et al. (2009), we found that the heritability of P300 amplitude in adolescent twins was not moderated by alcohol consumption. This finding is consistent with the hypothesis that reduced P300 amplitude reflects genetic risk rather than the effects of adolescent alcohol consumption.
