Can You Inherit Fear and Trauma?

Risk factors for numerous health conditions aren't the only problems our parents can pass on. Science is showing how we may inherit the effects of family tragedy.

It seems obvious that the histories of our parents and grandparents affect us. After all, the people who care for us determine everything about our early lives.

Scientists previously thought that history didn’t change the genetic makeups we inherit. Now, as they learn more about how genes are expressed, that basic idea is changing.

Compelling evidence of trauma passing through generations has come from a research team at New York’s Mount Sinai hospital led by Rachel Yehuda, PhD. The team studied the genes of 32 Jewish men and women who had either been interned in a Nazi concentration camp, witnessed or experienced torture, or had to hide during World War II.

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While it’s true DNA doesn’t change because of experience, chemical tags, called “epigenetic tags,” attach themselves to our DNA, switching genes on and off. Environmental influences — such as smoking, diet, and extreme stress — can affect those tags, which, the research suggests, can be passed on to children. The team found the same tags on a stress-related gene between the parents and their children. In a control group of Jewish parents who didn’t experience this kind of trauma and their children, the tags didn’t match.

Other examples suggest this process. Girls born to Dutch women, who were pregnant during a severe famine at the end of World War II, turned out to be more at risk for schizophrenia. In another study, researchers found evidence that the adolescent sons of males who smoke before puberty are more likely to be obese.

Scientists had thought that the tags disappeared after fertilization. But research by Azim Surani at Cambridge University and colleagues found that some tags slip through. How long the tagging sticks remains unclear.

From research in mice, scientists have shown that children and even some grandchildren can inherit a specific fear. Scientists at Emory University in Atlanta exposed male mice to the smell of cherry blossoms alongside a small electric shock. The mice eventually shuddered at the smell even if they weren’t shocked.

In the next two generations, pups also shuddered at the smell of cherry blossom when they encountered it for the first time — without having been shocked. The pups turned out to have more cherry blossom smell receptors in their brains.

As the researchers expected, the pups of control-group mice, trained to fear either other smells or no smells, didn’t fear the cherry blossoms.

Scientists are looking at the contribution of epigenetic tags — also sometimes called “imprinting” — on obesity, cancer, allergies and asthma, and other conditions.

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