We also identified a potential association between rs472402 and factor F2, which we labeled “positive affect at baseline” (P = 2.53×10−7; log10BF = 4.33). Similar to the previous example, this SNP did not show marked differences among populations in 1000 Genomes, and an analysis of the Caucasian-only subset yielded consistent results (P = 4.62×10−5; log10BF = 2.47). Several other SNPs in strong linkage disequilibrium (LD) with rs472402 (r2 = 0.77–0.98) were also associated with the baseline positive affect factor (see Table S5). Friendliness, Elation, and Vigor baseline values for all three sessions have substantial positive loadings on this factor, while Anxiety and Confusion baseline values have substantial negative loadings (Figure 3A). Examination of the mean values of the raw phenotypic data for individuals in the upper and lower deciles of this factor show that Friendliness, Elation, and Vigor were markedly different across sessions and time points (Figure 3B). Rs472402 falls within the first intron of the gene SRD5A1, which codes for an enzyme that converts progesterone to allopregnanolone, among other functions [51]. The minor allele frequency of this SNP in
