In addition to the association between alcohol dependence and alcohol-metabolizing enzymes, γ-aminobutyric acid (GABA) receptor genes have also been associated with alcohol dependence. This association is of particular relevance because alcohol is an agonist of the GABA receptor. This region includes the subunit genes GABRG1, GABRA2, GABRA4, and GABRB1 (Fig. 2). Edenberg and colleagues20 evaluated this region in detail and found a strong association between GABRA2, encoding the α2 subunit of GABAA, and alcohol dependence. This association was replicated in multiple populations, and was found to be most strong in alcohol-dependent individuals with comorbid dependence on illicit drugs.21–24
