The MDD2000+ study is the largest GWAS for MDD reported to date, comprising 2431 cases with MDD and 3673 screened controls. Our analysis was of >1 M SNPs but none achieved genome-wide significance. Indeed, the quantile–quantile plots (Figure 1) show that the distribution of observed associations closely follows that expected under the null hypothesis. These results are consistent with other GWAS of MDD.11, 12, 13, 14, 15 Furthermore, comparison of our results with these other studies including formal meta-analysis of results from MDD2000+ and the next two largest studies12, 15 (a total of 5763 cases and 6901 controls) showed little evidence for replication between studies.
