A genetic similarity matrix was estimated for all individuals using 849 801 autosomal SNPs that passed quality control. After removing one individual of each pair with a genetic similarity >0.025, a subset of ∼12 000 individuals was retained for the analyses of neuroticism and extraversion (See Supplementary Information Table S2 for exact numbers for the combined sample and for specific study cohorts). Estimates of genetic similarities for each pair of ‘unrelated' individuals were normally distributed with mean of -0.0002 and s.d.=0.0043 (See Supplementary Information Figure S1).
