Violence leaves deep scars on victims. It is well known that the development of each individual depends on their environment, thanks in part to epigenetics. This connects each person's DNA to their life context (age, health, diet, etc.), activating or deactivating genes to adapt each person's body to their environment and experiences. Thus, highly stressful events can cause epigenetic changes as the body attempts to adapt to this new context.
These repercussions have been repeatedly observed in animal models (e.g., traumatized mice) and are also beginning to become evident in the human, from Holocaust survivors to Syrian refugees who lived through their country's bloody civil war. A new study analyzing the epigenetics of these refugees shows that these epigenetic modifications are passed down from generation to generation, accelerating the biological aging of the children of these victims. The study, conducted by researchers from Hashemite University in Jordan and the University of Florida in the United States, was published on February 27, 2025, in the journal Scientific Reports.
An epigenetic adaptation to stress that could become harmful
The authors' hypothesis was that evolution may have created epigenetic programming specific to severe stress, allowing individuals to adapt their response to this stress very quickly. In this hypothesis, the heritability of these epigenetic markers would allow offspring to be born already better adapted to this stress, taking advantage of the embryo's high developmental plasticity. But these short-term adaptations could become counterproductive in the long term, increasing the risk of developing certain diseases.
Three generations of people exposed to violence
To test this, the authors analyzed three generations of Syrian refugees currently living in Jordan, with different exposures to violence: direct (the person directly experienced these events), prenatal (the person was in their mother's womb when the mother suffered the violence), and indirect through germ cells, where the person's parents suffered the violence before having children, which could have left traces in their germ cells (which will give rise to sex cells, through which these markers could pass to the person).
The violent events in question were the 1982 massacre in the city of Hama (when a commando unit from the Muslim Brotherhood terrorist organization killed 70 people) and the civil war of the 2010s. Three generations emerged from the first event: grandmothers directly experienced the violence in Hama while pregnant; their daughters were exposed to it prenatally; and their children were not exposed directly, but through their germ cells. And two from the second event: mothers, directly exposed to the violence of the civil war and who were already mothers and pregnant at the time; their eldest children, also directly exposed to the violence; and the children they were carrying at the time of the violence, therefore exposed prenatally. These groups were compared to Syrian women who left Syria before 1980 and who did not experience a major violent event. A total of 131 people participated in the study, from 48 families.
An epigenetic signature of violence?
The authors analyzed the DNA methylation of all participants. This analysis revealed about thirty methylations that appear specific to this exposure to violence, being visible in the three generations of exposure, but not in the control group. There would therefore be an epigenetic "signature" of violence, and the more violence a person had experienced, the stronger this signature was. But for the moment, the evidence remains quite weak due to the small number of participants and needs to be confirmed by other studies.
These violences would have a greater impact when the exposure is prenatal.
The researchers also analyzed the participants' biological age to determine whether the violence they experienced could accelerate the aging process. This was not the case for all participants, but only for those exposed to violence as children or in the womb. This shows how harmful such violence can be for development, in particular in utero.
“We believe our work is relevant to all types of violence, not just among refugees, asserts in a press release Connie Mulligan, study director. Domestic violence, sexual violence, gun violence... nWe must study the consequences of this violence, we must take it more seriously.”
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