Research has shown that Holocaust survivors tend to have lower-than-expected levels of the hormone cortisol, which is associated with the body’s reaction to stressful or traumatic situations. More recent studies suggest that their children are similarly likely to show reduced levels of the hormone—but, as well, higher levels of a counteracting agent. Tori Rodriguez writes:
Like their parents, many [descendants of survivors] have low levels of cortisol, particularly if their mothers had post-traumatic stress disorder. Yet unlike their parents, they have higher-than-normal levels of [a] cortisol-busting enzyme. . . . The enzyme is usually present in high levels in the placenta to protect the fetus from the mother’s circulating cortisol. If pregnant survivors had low levels of the enzyme in the placenta, a greater amount of cortisol could make its way to the fetus, which would then develop high levels of the enzyme to protect itself.
Read more on Scientific American: http://www.scientificamerican.com/article/descendants-of-holocaust-survivors-have-altered-stress-hormones