We used Levene’s test  to identify SNPs that show heterogeneity of phenotypic variances (σi2) across the three genotype groups at each SNP locus (i = 0, 1, or 2). We first log10 transformed all five traits followed by a z-score transformation by subtracting the sample mean and dividing by the sample standard deviation (SD), and further Winsorized the z-score values at 4 SD. The transformed phenotype Y was then used to calculate Z, defined by the absolute deviation of each participant’s phenotype from the sample mean of his or her respective genotype group at a given SNP locus. For each trait, participating cohorts provided the necessary summary statistics for each genotype at each marker . Specifically, the per genotype group counts (n0s, n1s, n2s), per genotype means (Z¯0s,Z¯1s,Z¯2s), and per genotype group variances of Z (σ0s2,σ1s2,σ2s2) were centrally collected and meta-analyzed. The minimum number of observations per genotype group required is 30 participants per cohort.