After genotyping, there were 13 AA, 23 AG, and 4 GG genotypes available in a sample that was 91% Caucasian. This SNP was in Hardy Weinberg equilibrium in the combined sample (p= 0.18) as well as in the Caucasian subset (p= 0.55). Results with SNPs in high LD with rs279871 (r2 > 0.70) suggest that there may be an allelic dosage effect, with those individuals homozygous for the high risk allele having the greatest risk for alcohol dependence (Covault et al., 2004; Fehr et al., 2006). For this reason, all statistical analyses compared the subjects homozygous for the high risk allele at rs279871 (A, allele frequency = 0.61) to those heterozygous for this allele. Rather than combining the small group of four subjects who did not carry a high risk allele with the rs279871 heterozygotes, these subjects were removed from the primary analyses, but included with the AG heterozygotes in secondary analyses.
