A genome-wide linkage study of EEG beta power in the high-risk Collaborative Study on the Genetics of Alcoholism (COGA) sample found a linkage peak (i.e., a statistical indication that a particular section of a chromosome co-segregates with the trait within families) over a GABAA receptor gene (GABRA2) on chromosome 4 [22]. Subsequent studies across multiple, independent samples have found evidence for association between alcohol dependence and variation in GABRA2 [23–25] (for a recent exception see [26]). A genome-wide linkage study of power for three frequency bands (alpha, theta, and beta) in a sample of Plains American Indians showed evidence for convergent linkage peaks over the corticotropin releasing hormone binding-protein gene (CRH-BP) on chromosome 5 [27]. In the same study, variants in CRH-BP showed association with AUD in a Caucasian replication sample, and anxiety disorders in the Plains Indians, suggesting that CRH-BP may have pleiotropic effects (i.e., associations with multiple disorders). More recently, gene-based tests from a whole-genome sequencing study of EEG beta power identified the gastrulation brain homeobox 2 gene (GBX2) on chromosome 2; however, it is unknown whether this gene is associated with AUD [28].
