Against this background, Edenberg (2004) genotyped SNPs across the GABA cluster on chromosome 4p and reported evidence of an association between alcoholism and single nucleotide polymorphisms (SNP) in the GABRA2 gene, which codes the GABA-A receptor's α2 subunit. This same report also noted an association between β-EEG oscillations and GABRA2 variation. The association of SNPs in GABRA2 and alcohol dependence has been replicated in several independent reports (Covault et al., 2004; Lappalainen et al., 2005; Soyka et al., 2008). Subsequent analyses using the same dataset as Edenberg et al (2004) have refined the association: Agrawal et al. (2006) reported that the GABRA2 association was limited to alcoholism with co-morbid drug dependence, while in analyses of adolescents Dick et al. (2006) found that SNPs in GABRA2 were associated with conduct disorder but not alcoholism. Other studies have found no association between alcoholism and the GABRA2 gene (Enoch et al., 2009; Enoch et al., 2010; Onori et al., in press), or have found the GABRA2 association with alcoholism to be mediated by anxiety (Enoch et al., 2006). Nevertheless, others report a relationship
