These findings, however, have mainly involved only male subjects. Studies investigating the relationship between P3 and SUDs/EXT in females are fewer and the results equivocal. Some studies find reduced P3 in female alcoholics (Hill & Steinhauer, 1993; Prabhu et al., 2001) and females at high-risk of developing alcoholism (Porjesz et al., 1998; Van Der Stelt, 1999), while other studies find no significant P3-AR in female alcoholics (Hill, Locke, & Steinhauer, 1999; Parsons, Sinha, & Williams, 1990). Across genders, when P3-AR is present, it tends to be enhanced more for males than females (e.g. Iacono & McGue, 2006; Porjesz et al., 1998; Yoon et al., 2006). Thus, evidence suggests a differential association between P3 and SUDs/EXT as a function of gender. Nonetheless, P3 has been shown to be strongly heritable (van Beijsterveldt & van Baal, 2002; Yoon et al., 2006), and it has been linked to genes putatively underlying EXT spectrum disorders, particularly alcoholism. Williams et al. (1999) found that reduced P3 amplitude and an alcoholism diagnosis were jointly linked to a region on chromosome 4 near the alcohol dehydrogenase gene
