The most robust candidate gene finding to date for AUD and related phenotypes is for GABRA2, initially identified by linkage scans.45,46 The GABAA gene cluster on chromosome 4 includes the GABRA2, GABRG1 and GABRB1 genes that together encode the α1β1γ1 GABA receptor that is almost exclusively found in the reward pathway. Numerous studies, nearly all in European-ancestry individuals but also one study in Plains American Indians, have replicated this association although there have also been negative studies, notably in African American samples.54 One study with similar results in both Plains American Indians and Finnish Caucasians showed that there are likely to be independent, complex contributions from both adjacent genes GABRG1 and GABRA2 to AUD vulnerability.55 A recent study showed an association between GABBR1, a GABAB receptor encoding gene, and AUD that was likewise replicated in Finnish Caucasians and Plains Indians.56 Other AUD associations for both Plains American Indians and Finnish Caucasians have been found for GAL, a gene encoding the neuroendocrine peptide galanin57 and HNMT, that encodes histamine N-methyltransferase, implicated in metabolism of histamine.58 An earlier study found that 5-HTR1B,
