GABRA2 gene, but not other members in the gene cluster, were associated with both ethanol dependence and changes in β-frequency electroencephalogram (EEG). Brain oscillations measured by EEG are a key phenotype in ethanol dependence: alcoholics and the offspring of male alcoholics have increased power in the β-frequency band (13–18 Hz) of the EEG (Costa and Bauer 1997). The association of GABRA2 markers with ethanol dependence was subsequently replicated in several independent studies in different populations (Agrawal et al. 2006; Bauer et al. 2007; Covault et al. 2004; Enoch et al. 2006; Fehr et al. 2006; Lappalainen et al. 2005; Soyka et al. 2008). Within these studies, strong association of the GABRA2 gene was found in European ancestry alcoholics without co-morbid drug dependence or major depression (Covault et al. 2004), although results from the COGA study reported the opposite (Agrawal et al. 2006). The association of GABRA2 with alcoholism was linked to anxiety scores (Enoch et al. 2006) and to severity of ethanol withdrawal (Fehr et al. 2006; Soyka et al. 2008), thus potentially influencing treatment outcome (Soyka et al. 2008). Indeed, Bauer et al. (2007) found that genetic vulnerability at the GABRA2 gene influenced the ability of different psychosocial treatments
