Based on converging evidence, P300 amplitude reduction (P3AR) has been proposed as an endophenotype (Gottesman & Gould, 2003), or, a genetically transmitted risk marker for alcoholism (Hesselbrock, Begleiter, Porjesz, O’Connor, & Bauer, 2001; Iacono, Carlson, Malone, & McGue, 2002). P3AR has been linked to risk for alcoholism across a variety of experimental tasks and in a variety of clinical and epidemiological populations (Carlson, Iacono, & McGue, 2004; Habeych, Charles, Sclabassi, Kirisci, & Tarter, 2005; Iacono, Carlson, et al., 2002; Porjesz & Begleiter, 1996; Porjesz et al., 1998), including adolescents at high familial risk for alcoholism at a young age prior to alcohol exposure (Begleiter, Porjesz, Bihari, & Kissin, 1984; Viana-Wackermann, Furtado, Esser, Schmidt, & Laucht, 2007). P300 amplitude has also been found to be heritable (heritability refers to the proportion of variability in P300 amplitude estimated to be due to genes) in twin and family studies (van Beijsterveldt & van Baal, 2002).
