In the final model, over two-thirds of the variance in PTSD (71 %) and AD (72 %) were attributable to additive genetic effects, with the remainder accounted for by individual-specific environmental influences. By contrast, only 28 % of variance in trauma exposure was accounted for by genetic factors. Unlike either PTSD or AD, to which there was no evidence of significant shared environmental contributions, 33 % of variance in trauma exposure was attributable to C. A considerable degree of overlap was observed between the two genetic factors, with rA1–A2=0.54, CI 0.31–0.66. Individual-specific environmental influences on trauma exposure were highly correlated with those contributing to PTSD (rE1–E2=0.75, CI 0.29–0.82) and modestly correlated with those contributing to AD (rE1–E3=0.13, CI 0.04–0.38), but CIs for covariance in E between AD and PTSD included 0, so this pathway was not included in the final model.
