based on results of twin correlations. In our sample, the DZ correlations were greater than half the MZ correlations for trauma exposure (rDZ=0.51, rMZ= 0.60) and AD (rDZ=0.45, rMZ=0.71). In the case of PTSD, the twin correlation for DZs was less than half that for MZs (rDZ=0.19, rMZ=0.69). We therefore tested an ADE model in the univariate analysis. D could be dropped without a significant change in model fit, so we fitted an ACE model to represent genetic and environmental influence on the three phenotypes in the trivariate analysis.
