An extensive literature now supports P3AR as an endophenotype for a variety of disorders that often precede or co-occur with alcoholism, including childhood disruptive disorders, antisocial personality disorder, nicotine dependence, and illicit drug addiction (Iacono, et al., 2003). A developmental model that can account for the genetic influence on these externalizing spectrum disorders and their link to P3AR holds that individuals inherit a general liability toward a variety of traits, behaviors and disorders reflecting a tendency toward behavioral disinhibition, which consists of difficulty inhibiting socially undesirable, restricted, or even proscribed behaviors (Iacono, Malone, & McGue, 2008), see also Zucker et al. (Zucker, Nigg, & Heitzig, This Issue). Although a full explication of this model is beyond the scope of this paper, we present a schematic view (Figure 2) to highlight features of the model most relevant to P3AR. Multiple sources of evidence from cross-sectional and prospective studies lend support to the model and attest to the strength of P3AR as an endophenotype for externalizing tendencies.
