Trauma Through Time

The interview with neuroscientist Ina Filla, PhD, explores the concept of transgenerational trauma, focusing especially on the Holocaust. It explains how traumatic experiences can be transmitted across generations through epigenetic mechanisms, socialization, and bonding. Filla outlines the biological basis of these transmission pathways based on current research, including animal studies, and discusses the complex psychological and societal impacts of inherited trauma.

C.B.: At a party, I asked you whether it’s true that the Holocaust can still be detected in people’s DNA, even in the third generation. Your reaction was clear?

I.F.: Yes, in fact, Holocaust research assumes that all Jews in Europe—regardless of how they survived the Holocaust—are affected by the trauma of persecution. And as we now know, trauma can be passed on to subsequent generations through various pathways: through epigenetics, through socialization, or through the bond between mother and child. This means that the traumatic experiences of our grandparents or great-grandparents may still have an impact on our own generation.

C.B.: Could you briefly explain what a psychological trauma is?

I.F.: In the International Classification of Diseases (ICD-10) by the World Health Organization, a traumatic experience is defined as an event that is so overwhelming and threatening that it far exceeds an individual's coping capacity. It is accompanied by feelings of helplessness and powerlessness, and results in a lasting disturbance of one’s understanding of self and the world. In other words, the familiar rules of life are thrown off balance—either briefly or for a long time. This can be caused by a serious accident or a natural disaster, or by being the victim of torture, terrorism, rape, or other crimes.

C.B.: How does trauma transmission work in epigenetics?

I.F.: Memories themselves cannot be inherited. So the inner images of your grandmother’s wartime experiences cannot be directly passed on to her granddaughter. But intense stress experiences can be transferred to the child on a molecular level. This is called transgenerational epigenetics.

This kind of trauma transmission has been studied in mice. Researcher Isabelle Mansuy from ETH Zurich, for example, separated newborn mice from their mothers—a traumatic experience for the young animals. This shock later led to symptoms such as depression and antisocial behavior—observable and measurable traits in the mice.

To rule out the possibility that the trauma was passed on through the behavior of traumatized parents—for example, through altered bonding or socialization—scientists used artificial insemination. The pups were carried and raised by surrogate mothers with no prior trauma. Yet the animals still suffered from the consequences of their genetic parents’, grandparents’, or even great-grandparents’ trauma.

This proved that trauma can be passed on biologically—via eggs or sperm—through at least three generations. A likely carrier of this information is RNA (ribonucleic acid), a biomolecule similar to DNA that changes in response to environment, lifestyle, or traumatic events. Another possible mechanism is DNA methylation: small chemical tags, called methyl groups, attach to the DNA and determine whether a gene is read and activated or not.

C.B.: What exactly does epigenetics mean?

I.F.: Epigenetics refers to how environmental influences affect our genes—this has now been well documented. My favorite example involves small children wearing socks. If toddlers under the age of three always wear socks, a gene that regulates temperature sensitivity changes, and those children may become extremely sensitive to cold. With my own daughter, it was the opposite: she refused to wear socks and never seemed cold, even with bare feet on cold stone floors in the middle of a Berlin winter.

C.B.: One could argue that there’s trauma from wartime on the perpetrator side as well. Does trauma manifest differently in the epigenetics of victims versus perpetrators?

I.F.: Every war inevitably causes trauma. But what’s particularly significant for Holocaust victims is the systematic annihilation of identity, personality, and individuality as a human being—what we now understand to have occurred through the process of dehumanization in concentration camps.

The Italian author Primo Levi, himself a survivor of Auschwitz, described these different layers of destruction. He said that the process of dehumanization—taking away people’s identity, habits, clothing, and literally everything—lets one grasp the double meaning of the term extermination camp. This dehumanization culminated in the tattooing of numbers into people’s skin—at that moment, they lost their names.

The trauma of identity loss manifests, for example, in survivors’ statements like “I am a different person now,” or even more broadly: “I am not a person.”

C.B.: I’ve found that many people react dismissively to this subject. How does that fit with the number you gave me—that 60% of children from the WWII era were traumatized, and that some of this trauma was passed on to future generations?

I.F.: That’s a very good question. Two things are worth noting. First, transgenerational epigenetics—meaning genetic trauma transmission across generations—has not yet been definitively proven in humans. It’s extremely difficult to distinguish between genetic and epigenetic inheritance, and also to separate epigenetic inheritance from environmental and cultural influences. That’s why the topic remains controversial among experts.

Second, trauma is a complicated subject. Even when we ourselves have experienced trauma, we often cannot fully access it, because trauma is often dissociated—split off from consciousness. If it remains unprocessed, many aspects of it stay buried in the unconscious.

Now imagine what that means for inherited trauma—traumas we haven’t experienced ourselves. It’s difficult to grasp. And if one does try to imagine it, the idea is likely accompanied by fear: because inevitably the question arises—how on earth is a trauma supposed to be resolved if it doesn’t even reside in my own unconscious, but rather in that of my parents, grandparents, or great-grandparents?

Interestingly, it is often the unspoken traumas—the ones that stay buried in the unconscious—that have the most severe effects on subsequent generations.