Previous association studies have shown the SNP4 A-allele, SNP5 G-allele, and SNP6 C-allele to be over-represented among subjects with alcohol dependence (Covault et al., 2004; Lappalainen et al., 2005). The risk of alcohol dependence has been associated with a low level of response to alcohol, as measured by subjective feeling of intoxication following an alcohol challenge (Bauer and Hesselbrock, 1993; Schuckit, 1984, 1994; Schuckit et al., 1996). A family history of alcohol dependence has also been associated with a diminished response to alcohol in nonalcoholics (Moss et al., 1989; Newlin and Thomson, 1990; O’Malley and Maisto, 1985; Pollock, 1992; Savoie et al., 1988; Schuckit, 1984; Schuckit et al., 2000). Monozygotic twins show greater similarity in sensitivity to an alcohol challenge than do dizygotic twins (Heath and Martin, 1992; Martin et al., 1985; Viken et al., 2003), providing evidence that alcohol sensitivity is an inherited trait. In view of this, our findings are consistent with the hypothesis that the risk of alcohol dependence associated with the A allele at SNP4, the G allele at SNP5, and the C allele at SNP6
