Trauma seems to be passed down genetically — but experts still aren't sure what that means

Trauma is an experience so harrowing that it can alter our gene expression — and in some cases, these changes can be passed down to future generations. But if the traumas experienced by our parents, grandparents and other ancestors can be directly transmitted to us through our genes — and presumably, we pass down our own psychological residue to our kids — what does that mean exactly? Are we doomed to an endless cycle of genetic anguish?

A growing body of research is shedding light on this phenomenon. For example, a 2020 paper published in the American Journal of Psychiatry analyzed blood samples of Jews who directly experienced the Holocaust, comparing them with both the blood samples of their children and the blood samples of Jews who lived outside of Europe during the Holocaust. Notably, the scientists found that mothers who survived the Holocaust had changes in their DNA in the sections that regulate stress responses — and that their children, who did not experience the Holocaust, had those same changes.

So this proves that intergenerational trauma is both real and biologically based, right? Not so fast says Dr. Rachel Yehuda, director of the Center for Psychedelic Psychotherapy and Trauma Research at the Icahn School of Medicine at Mount Sinai. Yehuda has done other research on intergenerational trauma and, when speaking with Salon by email, she emphasized that there is still a lot more work that needs to be done before more conclusive statements can be made.

"I don’t think we can say anything 'for sure' about genetic or environmental factors that lead to intergenerational effects," Yehuda said. "We can measure things in blood and maybe [the] brain that we think associate with intergenerational effects, but we don’t know much about the mechanisms of transmission or even how to fully interpret what we see."

Because the data that experts have obtained are always from single points in time, they are correlative — that is, while a link can be proven, it is not definitive that the one development has actually been caused by the other.

"These data serve us best when they generate hypotheses to explore in more rigorous studies, not when we use them to try to 'explain' why we behave the way we do in the here and now," Yehuda explained.

According to Dr. Sophie Isobel, a senior clinical lecturer at the University of Sydney who has also studied intergenerational trauma, scientists know very little for sure about the causes of this specific type of trauma, but they do know that trauma more broadly is passed from generation to generation by a number of variables.

Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter Lab Notes.

"We know that trauma can directly and indirectly affect across generations and that this is likely due to a mix of behaviors, sociocultural factors, exposure, patterns, biological factors, genetics and epigenetics," Isobel told Salon. "Across studies and populations, individuals in generations not directly exposed to trauma show traumatic effects similar to those who were directly exposed."

Although for a long time scientists believed this was primarily due to a person's environment, recent evidence suggests that there are biological factors involved as well — in particular, that sinewy area of genetics known as epigenetics.

"Epigenetics is about how certain genes can get turned on and off in response to environment," Isobel explained, comparing it to how caterpillars and butterflies have the same genetic material but look and act very differently based on their environment and life cycle. "Basically, the DNA itself doesn’t change — but how it is expressed does. It is proposed that intergenerational trauma can lead to cellular changes that alter the expression of genetic material, which over time become encoded, and that it is a vulnerability to traumatic effects that is passed across generations and then ‘activated’ or not activated by environmental triggers."

Although the changes are not as drastic to a human as the metamorphosis from a caterpillar to a butterfly, Isobell said "there is research demonstrating impacted psychosocial functioning and wellbeing in second and third generations, even when life is stable and safe."

While this analysis sheds light on individual instances of intergenerational trauma, it also raises questions about collective intergenerational trauma. When one looks at the current wars going on in Israel, Ukraine and elsewhere, it is natural to wonder about the role played by intergenerational trauma in both fostering and perpetuating those conflicts. To what extent are Israelis and Palestinians alike motivated by the past human rights violations that their ancestors endured? Will the conflict in Ukraine lead to intergenerational trauma passed on by Ukrainian parents to their children?

"There is a crucial difference between generations who are safe and living in non-traumatic contexts but are impacted by the experiences of their parents, grandparents or ancestors [versus] people, families or cultures who are impacted by trauma transgenerationally," Isobel pointed out. "In populations where exposure to trauma is widespread and sustained, epigenetic changes can become hardwired to enable survival and it can be very difficult to separate out direct trauma responses and those passed down across generations. Trauma of past generations and present don’t exist as discrete occurrences — they blur into a way of being and knowing, reinforced by environmental factors and events."

Isobel added, "In these situations, intergenerational trauma compounds primary trauma leading to complex experiences of transgenerational trauma."

Perhaps the best way of understanding intergenerational trauma is to keep in mind that, as Yehuda put it, "what we do know or can observe in people who have an ancestral legacy of trauma cannot be linked to the biology at this point."

In addition, there probably is no single response to intergenerational trauma that is easily identifiable: "Sometimes the fact that prior generations have undergone what you are going through makes your current situation seem more acute and intensifies emotions, but sometimes it reminds you that we survive things after all," Yehuda explained. In the end, while the science has yet to offer definite explanations for intergenerational trauma, what we do know for sure "is that in some form, we carry effects of our parent and grandparents' pasts with us. Our ancestors’ past matters."

Yehuda added, "Whether this helps us or hurts us or even whether we have control to use the legacy of these past experiences to our best survival advantage is something we need to learn a lot more about."