We tested for association at the level of genes using the versatile gene-based test for genome-wide association studies (VEGAS) [27]. While accounting for linkage disequilibrium (LD) and number of SNPs per gene, VEGAS aims to identify genes that show a higher signal of association than expected by chance, by considering all the p-values of all SNPs within genes (including ±50 kb from the 5′ and 3′ UTR). The gene-based association test was undertaken for 17,707 autosomal genes, we considered a p-value below α = 2.8×10−6 (0.05/17,707) to be significant. Since the MAOA gene is located on the X chromosome and sex chromosomes are not taken into account in VEGAS, we specifically checked all the SNPs in the MAOA gene that were covered in our dataset, to test if we could replicate the previously reported association in this gene.
