Although the association is replicable, no specific causative variant has been reported, nor is a mechanism of action known. Interestingly, however, Pierucci-Lagha et al. (2005) found an allelic association of a GABRA2 allele with the subjective response to alcohol in a sample of healthy subjects. Further, Bauer et al. (2007) found that individuals with a GABRA2 allele associated with risk for AD in some studies had higher daily probabilities of drinking and heavy drinking in a longitudinal study of the psychotherapeutic treatment of the disorder. The polymorphism also moderated the response to the specific psychotherapies examined in the study. However, markers in the 3′ region of GABRA2 (which is the region associated) are in linkage disequilibrium (LD) with markers at the adjacent locus, GABRG1, in many populations, including EAs (Ittiwut et al. 2008; Covault et al. 2008). This raises the possibility that the GABRA2 association is driven at least in part by variants in GABRG1, with risk loci in both genes (Covault et al. 2008; Enoch et al. 2009).
