(2008) replicated association to GABRA2, but their findings differed in the nature of the association and the specific variants that were associated with AD, respectively. There have also been non-replications of the association (Drgon et al. 2006; Matthews et al. 2007), though these studies differed substantially from the other studies in the methods of phenotyping and ascertainment employed. The three samples studied by Drgon were ascertained from among polysubstance abusers and a small sample of primary alcoholics from COGA. Matthews et al. (2007) ascertained subjects using information from the diagnostic interview schedule, an unstructured clinician’s interview, and family history report by participating relatives. They derived a “best-estimate” diagnosis based on Feighner criteria and DSM-III (which differs substantially from subsequent iterations of the DSM, the diagnostic systems used in the studies showing association to GABRA2).
