Within the substance use literature, the most widely studied GABAergic gene is GABRA2 on chromosome arm 4p12 [85]. The most promising results for this gene have been with alcohol dependence although subsequent studies have also shown it influences liability to other substance use disorders. We are aware of two human association studies that specifically examined the association between SNPs in GABRA2 and cannabis-related behaviors. In the first study, [92] conducted in the Collaborative Study of the Genetics of Alcoholism (COGA), a synonymous (a mutation that does not change the amino acid it codes for) polymorphism (rs279858) was associated with DSM-IV cannabis dependence. Recently, Lind et al. [93] reported no association between rs279858 and a frequency of cannabis use across the lifetime. A third study has also identified polymorphisms in GABRA2 for their influence on a composite measure of antisocial drug dependence [94].
