The intergenerational transmission of trauma is a controversial topic in psychology. But new research suggests that intense trauma can in fact be passed down to future generations.

The study, published in the journal Psychiatry Research, provides preliminary evidence that grandchildren of Holocaust survivors may be more susceptible to anxiety induced by Islamic State (ISIS) atrocities — but only under certain conditions.

“Almost everyone I know has been exposed to ISIS media (e.g. executions) and no one has ever researched if such viewing is associated with any psychological stress,” the study’s corresponding author, Yaakov Hoffman of Bar-Ilan University, told PsyPost.

“It was interesting to myself and my co-author Professor Amit Shrira to address if such ISIS anxiety would be greater in grandchildren of Holocaust survivors, i.e., if the intergenerational trauma of the Holocaust is associated with higher levels of ISIS anxiety. The reason behind this second objective is partly practical in terms of offering suitable interventions to clients as well as theoretical — as recent meta-analytic studies suggest that trauma does not transfer from one generation to the next.”

“After carefully reading the literature, we found three key factors that may be relevant to intergenerational transmission: the number of grandparent survivors, whether the type/context of trauma is similar (i.e., whether the Holocaust is reverberated by ISIS’s deeds and rhetoric), and whether the grandchildren themselves experienced trauma, in which case their own resilience should be less robust.

As far as the context of trauma being similar, Hoffman said “ISIS has been carrying out genocide of Yazidis as well as making threats to destroy Israel by making a second Holocaust.”

The study examined 241 Jewish Israelis who were in Israel during the 2015-16 Terror Wave and who had four grandparents of European origin who lived during World War II. The researchers split this sample into three groups: 71 individuals who had no Holocaust survivor grandparents, 114 who had one to three survivor grandparents, and 56 who had four survivor grandparents.

The participants were surveyed about their exposure to recent terrorist attacks, their consumption of ISIS-related media, their anxiety about ISIS, and PTSD symptoms.

The researchers found that the number of Holocaust survivor grandparents had no impact on ISIS anxiety among participants with few PTSD symptoms. However, the number of Holocaust survivor grandparents did appear to have a small influence on participants with more severe PTSD symptoms.

“Grandchildren whose all four grandparents were survivors and who have experienced their own PTSD symptoms showed greater ISIS anxiety than all other subjects,” Hoffman explained.

Participants who had four Holocaust survivor grandparents and PTSD symptoms were the most likely to strongly agree with statements such as “I am worried about ISIS more than most people”, “The threat of ISIS arouses a strong anxiety in me,” and “I sometimes imagine what will happen if I will fall at the hands of ISIS.”

The findings do not, however, indicate that there is a greater propensity to develop PTSD symptoms in descendants of Holocaust survivors.

“In contrast to some recent studies, the question may not be whether intergenerational transmission exists,” Hoffman told PsyPost, “but rather both what are the necessary conditions for revealing intergenerational transmission and what are the psychological (e.g., context theory/memory) and biological (e.g., epigenetics) mechanisms underlying such effects?”

Hoffman said the study has a number of caveats to take into account.

“There are caveats in terms of the type of sampling (convenience sample), the cross sectional nature which may preclude causality, the fact that we sampled Israeli Jews, who have suffered many decades of terror. Future studies are required to see if such findings replicate to other countries and cultures. Finally, we did not have information regarding the grandparents’ experiences during the Holocaust.”

How intergenerational trauma could be transmitted is still uncertain. But research published last year provides a clue. That study found that Holocaust survivors and their children showed changes in the epigenetic regulation of genes.