There has been one AI GWAS using resting EEG power as an intermediate phenotype for AUD, performed in a sample of 322 Plains American Indians.53 Although the diagnostic phenotype of AUD did not generate genome-wide significant statistical signals, the EEG GWAS identified three genes, one of which (SGIP1) was associated with AUD, an effect that might be mediated via the same brain mechanisms as for EEG power. Convergence of findings at the sub-threshold level with previous findings in genetic studies of addictions provided evidence that the intermediate phenotype approach can potentially identify genes that have a general effect on addiction even in datasets of modest size, notably of population isolates such as AI/AN.53
