Several GABA receptor genes are associated with alcoholism. The association of GABRA2 with alcoholism (Edenberg et al., 2004) has been replicated in case-control studies of Germans (Fehr et al., 2006; Soyka et al., 2008), Russians (Lappalainen et al., 2005), European-Americans (Covault et al., 2004), Plain Indians (Enoch et al., 2006), and a general Australian population (Lind et al., 2008). The association was with SNPs in a region of linkage disequilibrium (LD) extending from intron 3 past the 3′ end of the GABRA2 gene (Edenberg et al., 2004; Covault et al., 2004) and may extend to the 5′ end of the adjacent GABRG1 gene, which is in LD with SNPs in GABRA2 (Covault et al. 2008). In the COGA sample, the association with GABRA2 was greatest among those alcohol dependent individuals with comorbid dependence on illicit drugs (Agrawal et al., 2006); this subgroup is characterized by greater severity of alcohol problems (Dick et al., 2007). SNPs in GABRG3 on chromosome 15 (Dick et al., 2004) and GABRA1 on chromosome 5 (Dick et al., 2006) have also been associated with alcoholism. The
