Six of the 12 previously identified loci were also significant in this study. Even though some previously identified loci demonstrated weaker association here, their associations remained strong, and there was almost complete concordance in the direction of association between top-associated variants in this study and ADHD2019. In GWAS of complex disorders, it is not uncommon for some loci to fluctuate around the significance threshold with increasing sample sizes until they eventually achieve stable significance; this can often be attributed to the “winner’s curse” phenomenon, where effect size estimates close to the discovery threshold tend to be overestimated in initial GWAS42.
