In the Southwest American Indian and Plains Indian populations, associations between alcohol-related phenotypes and polymorphisms in several GABA receptor genes have been tested. A region of chromosome 4p containing GABRA2, GABRB1, and the GABA 1G receptor gene (GABRG1) has been identified as a susceptibility locus in previous linkage scans of alcohol dependence and quantitative EEG traits in the COGA sample [34]. Additionally, polymorphisms in GABRA2 and GABRG1 have shown evidence of association with alcohol use phenotypes [40]. In the Plains Indian sample, GABRA2 and GABRG1 polymorphisms have yielded evidence of association with alcohol misuse diagnoses [54-55]. In the Southwest American Indian sample, a second GABA receptor gene cluster located on chromosome 5q34 containing the GABA 1A (GABRA1), GABA 6A (GABRA6), GABA B2 (GABRB2), and GABA G2 (GABRG2) receptor genes has also yielded evidence of association with alcohol dependence with evidence suggesting the association is due to a causal variant in GABRA6 [56]. Studies of other ethnic groups including Caucasian [57] and Asian populations [58] have reported similar associations with GABRA6 polymorphisms.
