There is evidence that the P3 amplitude is directly related to the number of first-degree alcoholic relatives and not the drinking history of an alcoholic (Pfefferbaum et al., 1991; Cohen et al., 1995) or FHP/HR individual (Benegal et al., 1995). In the COGA study, lower P3 was found in alcoholics and family members from densely affected families compared with those from control families (Porjesz et al., 1998). Family history was significantly and selectively associated with lower P3 amplitudes to alcohol-related stimuli in a group of young adult African American men and women; current use of marijuana and alcohol did not modify P3 amplitudes (Ehlers et al., 2003). In contrast, some studies have failed to find relationships between family history and P3b amplitude (Polich and Bloom, 1987; Ehlers et al., 2001; Houston et al., 2003). Most P3 studies on HR have focused on males; data for female offspring have been less consistent, suggesting a weaker effect (Hill and Steinhauer, 1993; Hill et al., 1995a). Data from the COGA study also showed lower P3 amplitude in female offspring from multiplex alcoholism families,
