not replicate in the follow-up sample (1-tailed pfollowup = 0.3) (Supplementary Data 2 & 3). This locus has been significant in recent 11,12,17,18 but not earlier BD GWAS 9,13,20. Thus, complex genetic architecture as well as phenotypic heterogeneity may contribute to the inconsistency of genome-wide significant findings within and across BD GWAS studies. The observed heterogeneity is a major challenge for GWAS of psychiatric disorders and calls for careful and systematic clinical assessment of cases and controls in parallel with continued efforts to collect larger sample sizes.
