Despite the modest sample sizes—small when compared to the very large GWASs of psychiatric disorders and other complex traits—our initial GWAS of oscillation strength already found significant loci for alpha band oscillations with plausible biological mechanisms. These associations will continue to be followed up as we further increase our sample sizes. Combining SNP results into gene‐based and gene‐expression tests, we observed significant associations with alpha oscillation strength and pointed to brain areas and genomic loci previously linked to psychiatric disorders. EEG oscillatory parameters may be less polygenic than other complex traits—although not to the degree as previously suggested or hoped for (see also de Geus, 2010). Nevertheless, genetic analyses of EEG features are starting to be helpful in explaining how specific psychiatric liability genes affect the functioning brain, plotting the pathway from SNP to expression to neural‐level function, to systems‐level function, and finally to behavior (de Geus, 2010; Iacono, 2018). Investigating these pathways will be greatly aided by increase sample sizes and by establishing the EEG features' polygenicity (Holland et al., 2019), as well as variant‐level joint‐polygenicity analyses that are
