World War II saw countless crimes against Jews. Millions were killed, and those who survived had their lives permanently scarred. But the harm may not have stopped there. A new study has found that the trauma experienced by Holocaust survivors caused genetic changes, which can be passed down to their children.
The results are an example of “epigenetic inheritance”—genetic changes caused by environmental factors, such as smoking, diet, or stress. In these cases, the underlying genetic code remains unchanged, but some of the chemical tags that get attached to genes throughout a person’s life get passed down.
The new study, published in Biological Psychiatry, is the first example that shows how epigenetic changes in humans caused by trauma can be inherited. The study involved 32 Jewish male and female Holocaust survivors, their 22 offspring, and a control group of people of similar demographic.
Only Holocaust survivors and their children showed chemical tags on the FKBP5 gene, which is associated with how people respond to stress. These chemical tags don’t alter how the gene works—rather, they regulate when the gene gets turned on or off, and can have a huge impact on how the person responds to stress.
Most epigenentic changes are erased before during the process of fertilization. However, in the past few decades we have found that some changes do slip through. How that happens is not clear. Our understanding remains rudimentary, because most of it comes from animal studies. For instance, rat mothers cause similar epigenetic changes when they lick their pups. The pups that were licked less have measurably high stress levels.
We are starting to observe correlations in human studies, too. A 2014 study showed that men who smoked before puberty fathered fatter sons than those who smoked after. Definitive genetic changes hadn’t been shown until now, but even they will have to be backed up with more rigorous studies.
The only good news is that, as far as we know, these epigenetic changes at most last only a few generations.