Despite the findings that the various measures are likely substantially influenced by additive genetic effects, analyses of individual SNPs did not yield any evidence of genome-wide significant associations. Gene-based tests of all autosomal genes, which aggregate over all SNPs in a gene rather than examining each SNP by itself, did, yielding evidence of association between delta power and two genes. However, they are most highly expressed outside the brain, and the proximity of the two genes to each other suggests that this represents one signal, which is likely to be a false positive. Our analysis of 204 candidate genes selected because they are likely relevant to understanding EEG measures or related phenotypes also yielded an association between delta power and GABRA1, a gene that encodes the α1 subunit of the GABA receptor. GABRA1 has been associated with measures of alcohol consumption (Dick, Plunkett, et al., 2006). However, evidence of GABA system involvement in EEG is limited to high frequencies (Whittington et al., 2000). In addition, given the number of tests across different EEG measures, this one finding must be treated cautiously.
