Holocaust Victims Pass On Their Trauma Through Genes, Study

Holocaust survivors pass on genes influenced by trauma to their children as well as their grandchildren, according to theguardian.

A research team at New York's Mount Sinai hospital, led by Rachel Yehuda,studied 32 Jewish men and women who had either been "interned in a Nazi concentration camp, witnessed or experienced torture or who had had to hide" even as the second world war was raging.

When they examined their children's genes, who also had increased stress disorders, they compared them with other Jewish families who had lived outside Europe during the war. "The gene changes in the children could only be attributed to Holocaust exposure in the parents," said Yehuda.

The trauma is thus transferred in "epigenetic inheritance" with environmental influences such as smoking, diet and stress affecting the next few generations.

Researchers believe that children of holocaust survivors many have low levels of cortisol, particularly if their mothers had PTSD, but they have above average levels of the cortisol-busting enzyme. The adaptation happened in the womb, according to dailymail.

Hence, it is clear that genes are influenced by the environment with "chemical tags that attach themselves to our DNA", even as genes are switched on and off.

Moreover, there is even a tentative connection between generations. Hence, daughters of Dutch women who had been pregnant during a severe famine ran the risk of developing schizophrenia. Similarly, men who smoked before puberty were the fathers of "heavier sons than those who smoked after".

The team deeply examined a region of a gene associated with the regulation of stress hormones, which is affected by trauma. "It makes sense to look at this gene," said Yehuda. "If there's a transmitted effect of trauma, it would be in a stress-related gene that shapes the way we cope with our environment."

Hence epigenetic tags were found on the same part of the gene in both the Holocaust survivors and their children, even as a similar correlation was not found in the control group and their children.

The trauma had not been experienced by the children themselves, but had only been transmitted by the parents. "To our knowledge, this provides the first demonstration of transmission of pre-conception stress effects resulting in epigenetic changes in both the exposed parents and their offspring in humans," said Yehuda, whose work was published in Biological Psychiatry.

How do genes get passed on? Research by Azim Surani at Cambridge University and colleagues shows that some epigenetic tags escape the "cleaning process" of fertilisation.

Whether the gene in question survives or not impacts the method of making the stress hormone and the coping techniques, said Yehuda. "It's a lot to wrap our heads around. It's certainly an opportunity to learn a lot of important things about how we adapt to our environment and how we might pass on environmental resilience."

For years, the challenge has been to show that "intergenerational effects" are not just shifted through "social influences from the parents" or "through regular genetic inheritance", said Marcus Pembrey, emeritus professor of paediatric genetics at University College London.

"Yehuda's paper makes some useful progress. What we're getting here is the very beginnings of a understanding of how one generation responds to the experiences of the previous generation. It's fine-tuning the way your genes respond to the world.

Interestingly, even some kinds of fears might be inherited---at least in animals.

Scientists at Emory University in Atlanta made male mice fear the smell of cherry blossom by pairing the smell with a small electric shock. Eventually, the mice feared the smell.

Strangely, even if they had never smelt cherry blossom, the babies of the mice reacted with the same fear at the smell---shuddering even when they came in contact with it.

Other mice's children had no such fear.