The best-fitting trivariate Cholesky is shown with unstandardized path coefficients in Fig. 1 and summarized with standardized coefficients and 95 % confidence limits in Table 2. The final model was derived by conducting a series of tests. First, for each pheno-type we dropped the A and C variance components with values below 0.40 (A for trauma exposure and C for PTSD and AD) one at a time and compared the resulting submodels to the full model. Dropping the A pathway from trauma exposure resulted in a significant deterioration in model fit [Δχ2(3)=8.50, p=0.04], but removal of neither C pathway significantly impacted model fit. [For PTSD, Δχ2(3)=2.78, p=0.43 and for AD, Δχ2(3)=5.11, p=0.16.] In the second step, the C pathways were dropped simultaneously from PTSD and AD and the reduced model was compared to the full model. No deterioration in fit was observed [Δχ2(5)=4.44, p=0.49], so the reduced model was accepted. Next, we tested this reduced model against a model in which a single factor accounted for genetic influences on trauma exposure and PTSD and found no significant change in model
