P3AR characterizes each of the child and adult disorders in the externalizing spectrum (Iacono, Carlson, Malone, & McGue, 2002). It is also associated with different forms of disinhibited behavior, such as police contact and early sexual intercourse (Iacono & McGue, 2005) as well as early initiation of substance use and misuse (Iacono & McGue, 2005; Yoon, et al., 2006). The co-occurrence among externalizing spectrum behaviors, personality traits, and disorders can be modeled as a highly heritable latent trait (Kendler, Prescott, Myers, & Neale, 2003; Krueger, et al., 2002; Young, Stallings, Corley, Krauter, & Hewitt, 2000) which mediates associations between P3AR and each facet of the latent trait (Patrick, et al., 2006). This association is due to genes common to P300 amplitude and externalizing (Hicks, et al., 2007). Work by other groups also supports P3AR as an endophenotype for externalizing psychopathology and behavioral disinhibition more generally (e.g., Bauer & Hesselbrock, 2003; Gao & Raine, 2009; Habeych, Charles, Sclabassi, Kirisci, & Tarter, 2005; Hill, Steinhauer, Locke-Wellman, & Ulrich, 2009).
