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Violence and trauma leave inheritable markers on a person’s genome that persist over multiple generations, according to a new study coauthored by Yale anthropologist Catherine Panter-Brick.

The first-of-its-kind study focuses on epigenetic changes — chemical modifications to DNA that can affect gene function and individual characteristics — across three generations of Syrian refugees. It shows that women who have been directly affected by war-related violence and trauma indicate altered epigenetic markings — but so do their grandchildren, even if they had no direct exposure to warfare.

The study, which published on Feb. 27 in the journal Scientific Reports, was conducted by an international team led by women scientists working across disciplines. It is the latest in an ongoing suite of research the team has conducted to better understand the cognitive, physiological, and genetic signatures of stress and trauma in Syrian refugee children.

“The study documents the signatures of stress and trauma in the body, under the skin. Our findings present the first-ever evidence that violence can leave epigenetic marks on the genome, which has important implications for understanding evolution and how traumatic experiences can become embedded in the genome and persist for generations,” said Panter-Brick, the Bruce A. and Davi-Ellen Chabner Professor of Anthropology, Health, and Global Affairs in Yale’s Faculty of Arts and Sciences and at the Yale Jackson School of Global Affairs. 

“While our results focus on the violence of war, they are relevant to understanding the intergenerational consequences of sexual violence, domestic violence, and gun violence, and underscore the importance of violence prevention.”

The work would not have been possible without international collaboration and trusting relationships within the refugee communities, said study coauthor Rana Dajani, professor of molecular biology and genetics at the Hashemite University in Jordan, whose intimate knowledge of Jordan’s Syrian refugee population and its tragic history inspired the research project. 

“Our unique research design — studying three generations with local controls — was possible due to my dual role as scientist and community member,” said Dajani. “By engaging our own communities, we fostered trust and agency, allowing families to understand the biological impact of trauma on themselves and their offspring.”

For the study, the researchers recruited women from 48 refugee families in Jordan who had been pregnant during separate violent civil conflicts that erupted in Syria in 1980 and 2011. These included families in which the grandmothers had been pregnant during the 1982 Hama massacre, families in which mothers had been pregnant during the 2011 Syrian uprising and subsequent armed conflict, and a control group of families that had relocated to Jordan before the outbreak of violence in 1980. 

Study coauthor Dima Hamadmad, a Syrian researcher and the daughter of refugees, led the search for families that met the study criteria. She then collected data from the mothers, their children, and their grandchildren to compare direct, prenatal, and germline exposure to violence. (Germline cells form eggs and sperm). 

“I am deeply grateful to the Syrian families who opened their doors to me, trusting me with their stories and sufferings, hoping for acknowledgment, and believing in a better future for their children,” Hamadmad said. “Beyond its scientific significance, this research is a step toward exposing atrocities, breaking impunity, and ensuring justice. It’s about the trauma, both in the past and present, being exposed, documented, and acknowledged.”

In their analysis, the researchers examined 850,000 sites of DNA methylation (DNAm) — the most common epigenetic modification — among the study’s participants. They found that mothers and children who had directly experienced violence had altered epigenetic markings; they specifically identified 21 sites associated with direct exposure to violence. They also pinpointed 14 sites where DNAm was associated with germline exposure to violence. Overall, 32 of these sites showed a similar change in DNAm across all three exposures to violence — germline, prenatal, and direct — suggesting there is a common epigenetic signature of violence across generations and developmental stages.

Additionally, the researchers identified epigenetic age acceleration— a measure that indicates that an individual’s DNAm-predicted age is older than their chronological age — in association with prenatal exposure to violence in children. This, researchers say, highlights the critical period of in utero development.

Although most DNAm marks are erased before birth, the study provides evidence that some may persist across future generations, which would mean that the experience of violence is preserved and embedded in the genome, said Connie J. Mulligan, a professor of anthropology at the University of Florida and coauthor of the study.

“We propose that a small subset of methylation marks is environmentally sensitive and intergenerationally heritable that allow humans to adapt to environmental stressors, including psychosocial stress and violence,” Mulligan said. “Our results also highlight the amazing resilience and tenacity of traumatized populations around the world who have survived and even flourished in the face of adversity.” 

Panter-Brick directs the Conflict, Resilience and Health Program at the MacMillan Center for International and Area Studies at Yale and is co-director of the Jackson School’s Peacebuilding Initiative. She has a secondary appointment at the Yale School of Public Health.

Other study coauthors are Edward B. Quinn, Christopher L. Dutton, Lisa Nevill, all from the University of Florida, and Alexandra M. Binder of the University of Hawaii and the University of California, Los Angeles. The study was funded by the MacMillan Center, with a faculty grant to Panter-Brick, and by a National Science Foundation grant to Mulligan and Panter-Brick.