Chen et al., 2009; Chen et al., 2010) and related externalizing disorders as well (Dick, 2007; Dick et al., 2008). Quantitative electrophysiological phenotypes, such as EEG, P3, and related EROs, have served as effective endophenotypes for gene identification in psychiatric genetics (for recent reviews, see Porjesz and Rangaswamy, 2007; Rangaswamy and Porjesz, 2008; Iacono and Malone, 2011; Chen et al., 2012; Euser et al., 2012; Pandey et al., 2012; Rangaswamy and Porjesz, 2014; Kamarajan and Porjesz, 2015). These heritable neurophysiological biomarkers (Begleiter and Porjesz, 2006; Anokhin, 2014) have been very successful in identifying susceptibility genes for alcohol dependence and related disorders (Rangaswamy and Porjesz, 2008; Chen et al., 2012) as they are directly associated with human information processing and cognitive functions (Porjesz and Rangaswamy, 2007). Interestingly, several of the same genes associated with electrophysiological phenotypes and alcoholism in adults have been found to be related to precursor phenotypes in children and adolescents, such as conduct disorder (Dick et al., 2004), onset of regular drinking (Chorlian et al., 2013), and trajectories of drunkenness (Dick et al., 2014). While heritability of the reward-related P3 is yet to be determined, it may be another promising endophenotype, as both alcoholics (Kamarajan et al., 2010)
