Objective:

Twin studies have demonstrated that posttraumatic stress disorder (PTSD) is moderately heritable, and the pattern of findings across studies suggests higher heritability in females compared with males. Formal testing of sex differences has yet to be done in twin studies of PTSD. The authors sought to estimate the genetic and environmental contributions to PTSD, and to formally test for sex differences, in the largest sample to date of both sexes, among twins and siblings.

Methods:

Using the Swedish National Registries, the authors performed structural equation modeling to decompose genetic and environmental variance for PTSD and to formally test for quantitative and qualitative sex differences in twins (16,242 pairs) and in full siblings within 2 years of age of each other (376,093 pairs), using diagnostic codes from medical registries.

Results:

The best-fit model suggested that additive genetic and unique environmental effects contributed to PTSD. Evidence for a quantitative sex effect was found, such that heritability was significantly greater in females (35.4%) than males (28.6%). Evidence of a qualitative sex effect was found, such that the genetic correlation was high but less than complete (r_g=0.81, 95% CI=0.73–0.89). No evidence of shared environment or special twin environment was found.

Conclusions:

This is the first demonstration of quantitative and qualitative sex effects for PTSD. The results suggest that unique environmental effects, but not the shared environment, contributed to PTSD and that genetic influences for the disorder are stronger in females compared with males. Although the heritability is highly correlated, it is not at unity between the sexes.

中文翻译：

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在瑞典创伤后应激障碍的全国双胞胎兄弟姐妹研究中测试定量和定性性别影响

 目的：

双胞胎研究表明，创伤后应激障碍 （PTSD） 具有中等遗传性，研究结果模式表明女性的遗传性高于男性。在 PTSD 的双胞胎研究中尚未对性别差异进行正式测试。作者试图估计遗传和环境对 PTSD 的贡献，并在迄今为止最大的双胞胎和兄弟姐妹的两性样本中正式测试性别差异。

 方法：

利用瑞典国家登记处，作者进行了结构方程建模，以分解 PTSD 的遗传和环境方差，并正式测试了双胞胎（16,242 对）和彼此 2 岁以内的全兄弟姐妹（376,093 对）的定量和定性性别差异，使用来自医疗登记处的诊断代码。

 结果：

最佳拟合模型表明，加性遗传和独特的环境效应导致了 PTSD。发现了定量性别效应的证据，因此女性 （35.4%） 的遗传力显著高于男性 （28.6%）。发现了定性性别效应的证据，因此遗传相关性很高但不完全 （r_g=0.81,95% CI=0.73–0.89）。未发现共享环境或特殊孪生环境的证据。

 结论：

这是 PTSD 的定量和定性性别影响的首次证明。结果表明，独特的环境影响，而不是共享环境，导致了 PTSD，并且与男性相比，女性对这种疾病的遗传影响更强。尽管遗传力高度相关，但它并不是两性之间的统一。