Although influenced by some of the same heritable factors, low-risk trauma exposures differed substantially from high-risk trauma exposures in the degree of genetic overlap with MDD and PTSD. The genetic correlation of low-risk trauma with MDD and PTSD was 0.50 compared with 0.89 for high-risk trauma. Together with the finding that all the genetic variance in PTSD was attributable to heritable factors common to PTSD and MDD, the evidence suggests that nearly all the genetic influences on PTSD, MDD, and high-risk trauma exposure can be traced to the same sources. Identification of these sources is beyond the scope of the present study, but the limited research in this area suggests that heritable traits associated with depression and PTSD, such as neuroticism3,41,42 and propensity to externalizing behaviors,14,43,44 are likely possibilities.
