In the final model, 47% of the variance in low-risk trauma exposure and 60% of the variance in high-risk trauma exposure was attributable to additive genetic factors. Heritable influences accounted for 46% of the variance in PTSD and 27% of the variance in MDD. Nonshared environmental influences accounted for the remaining variance in all 4 phenotypes. There was no evidence of significant shared environmental contributions to PTSD, MDD, or either high-or low-risk trauma exposure. Additive genetic and non-shared environmental correlations among the 4 phenotypes are reported in Table 5. Moderate to high genetic correlations were observed between low-risk trauma exposure and high-risk trauma exposure (r =0.50), PTSD (r=0.57), and MDD (r=0.57). An extremely high degree of genetic overlap was observed with high-risk trauma exposure and both MDD (r =0.89) and PTSD (r =0.89). Complete correlation of genetic factors contributing to MDD and to PTSD (r =1.0) was observed.
