For EA and AA young adults there were significant associations between EXT PGS and externalizing behavior scores (βEA = 0.08, 95% CI 0.03 to 0.12; ΔREA2=0.01, 95% CI 0.00 to 0.01; βAA = 0.13, 95% CI 0.05 to 0.22; ΔRAA2=0.01, 95% CI 0.00 to 0.03; Table 2, Fig. 1a, b)†1 as well as significant main effects of sex (βEA = −0.26, 95% CI −0.30 to −0.22; βAA = −0.31, 95% CI −0.38 to −0.25). When the interactive effect of EXT PGS and sex was included in the linear regression models, there were significant improvements in the model for EA (β = −0.05, 95% CI −0.10 to −0.01) but not AA young adults (β = −0.05, 95% CI −0.14 to 0.01; online Supplementary Table 3). These results indicate that among young adults, the association between EXT PGS and externalizing behaviors was strongest for males.
