Although intended to be a statistical control rather than a focus of the current study, the results of genetic modeling of the trauma exposure phenotype merit comment. We found that 28 % of variance in trauma exposure could be accounted for by genetic sources. In the VETR sample, Lyons et al. (1993) reported 47% heritability for combat exposure. Stein et al. (2002) found no evidence for genetic influences on nonassaultive trauma, but estimated heritability for assaultive trauma at 20%. Our finding that 33 % of variance in trauma exposure was accounted for by shared environmental factors is closely aligned with Stein et al.’s estimates of 21 % and 39 % for assaultive and non-assaultive trauma respectively, but contrasts sharply with the absence of shared environmental influences reported in the VETR sample. With so few studies against which to compare our results, it is difficult to draw any definitive conclusions, but the greater similarity of our results to those of Stein et al. (2002) versus Lyons et al. (1993) suggests that the relative contribution of genetic and shared environmental influences may
