We present here the results of an initial case-control genome-wide association study (GWAS) of recurrent early-onset MDD using single nucleotide polymorphism (SNP) array technology. A companion article presents a second MDD GWAS in the STAR*D antidepressant effectiveness trial sample and a meta-analysis of the GenRED, STAR*D and publicly-available Genetic Association Information Network (GAIN-MDD) GWAS datasets.17 We did not observe genome-wide significant evidence for association in the GenRED or combined analyses. The meta-analysis demostrated increased statistical support for one of the top GenRED findings, for SNPs in the gene encoding the Sp4 transcription factor. Many of the most robust GWAS findings to date have been detected in samples of 10,000–20,000 cases (plus controls), with genotypic relative risks typically in the 1.1–1.2 range.18 Thus, larger samples will be required to clarify whether any of our findings represent true associations, and whether recurrent, early-onset MDD is a uniquely valuable phenotype for association studies.
