We intuitively understand, and scientific studies confirm, that if a woman experiences stress during her pregnancy, it can affect the health of her baby. But what about stress that a woman experiences before getting pregnant — perhaps long before?
It may seem unlikely that the effects of such stress could be directly transmitted to the child. After all, stress experienced before pregnancy is not part of a mother’s DNA, nor does it overlap with the nine months of fetal development.
Nonetheless, it is undeniable that stress experienced during a person’s lifetime is often correlated with stress-related problems in that person’s offspring — and even in the offspring’s offspring. Perhaps the best-studied example is that of the children and grandchildren of Holocaust survivors. Research shows that survivors’ children have greater-than-average chances of having stress-related psychiatric illnesses like post-traumatic stress disorder, even without being exposed to higher levels of stress in their own lives.
Similar correlations are found in other populations. Studies suggest that genocides in Rwanda, Nigeria, Cambodia, Armenia and the former Yugoslavia have brought about distinct psychopathological symptoms in the offspring of survivors.
What explains this pattern? Does trauma lead to suboptimal parenting, which leads to abnormal behavior in children, which later affects their own parenting style? Or can you biologically inherit the effects of your parents’ stress, after all?
It may be the latter. In a study that I, together with my colleagues Hiba Zaidan and Micah Leshem, recently published in the journal Biological Psychiatry, we found that a relatively mild form of stress in female rats, before pregnancy, affected their offspring in a way that appeared to be unrelated to parental care.
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