To estimate trans-ancestral prediction accuracy, GREX was calculated for 162 African-American individuals and 280 European individuals from the NIMH Human Brain Collection Core (HBCC) dataset (Supplementary Figure 2c). RR2 values were higher on average in Europeans than African-Americans (average RR_EUR2 = 0.048, RR_AA2 = 0.040), but were significantly correlated between African-Americans and Europeans (rho = 0.78, p < 2.2 × 10−16, Pearson test; Supplementary Figure 3).
