To confirm the findings from the pool-based GWAS, we sought to replicate our findings in silico in two cohorts: the Netherlands Study of Depression and Anxiety (NESDA; Penninx et al., 2008) and the Netherlands Twin Registry (NTR; Boomsma et al., 2006). The NESDA and NTR studies were approved by the Central Ethics Committee on Research Involving Human Subjects of the VU University Medical Center Amsterdam. Subjects were selected for a GWA for major depressive disorder (Boomsma et al., 2008; Sullivan et al., 2009) and the sample included 1738 depressed cases and 1802 controls. Details on the recruitment, sample composition, screening procedure and phenotype assessment are described in detail elsewhere (Boomsma et al., 2008). The number of AD and ND cases and controls is summarized in Table 2.
