For alcoholism, GWAS has been even less successful than for smoking. No alcohol dependence GWAS has yielded a finding of genome-wide significance.97–115 A large meta-analysis of GWAS on alcohol consumption was recently conducted in 12 population-based samples of European ancestry, totaling 26,316 individuals. The most significant associated marker, namely rs6943555, mapped to the autism susceptibility candidate 2 gene (AUTS2). Rs6943555 was found to moderate AUTS2 expression in human postmortem brain from the prefrontal cortex. Differences in expression of AUTS2 were found in whole-brain extracts of mice selected for differences in voluntary alcohol consumption.116 Recently, multiple genome-wide significant loci for resting electroencephalogram (EEG) were identified by GWAS,117 illustrating the potential power of combining GWAS with the endophenotype strategy. GWAS of neuroimaging responses relevant to addiction such as those exploring impulsivity and reward are under way.
