Violence and Genetics: A Lasting Impact Across Generations

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Source: University of Florida *

A groundbreaking study conducted by researchers at the University of Florida has uncovered evidence that violence can leave lasting marks on human DNA, persisting across generations. The research, published on February 27, 2025, in Scientific Reports, provides the first human evidence of stress-induced epigenetic changes being passed down to grandchildren. This discovery sheds new light on the intergenerational effects of trauma and could help explain long-standing cycles of violence, poverty, and abuse worldwide.

The Hama Massacre and Its Genetic Legacy

In 1982, the Syrian government launched a brutal siege on the city of Hama, killing tens of thousands in a sectarian attack. Decades later, this event played a role in inspiring rebels to rise against the Assad regime. However, beyond its historical and political ramifications, the massacre appears to have left a biological imprint on the descendants of survivors.

Researchers found that the grandchildren of women who were pregnant during the siege—despite never experiencing violence firsthand—exhibited genetic modifications inherited through their mothers. This marks the first time a phenomenon previously observed in animals has been confirmed in humans: the transmission of stress-induced genetic changes across generations.

Epigenetics: A Mechanism for Transmitting Trauma

While direct changes to DNA sequences do not occur due to life experiences, epigenetics—a system that regulates gene expression—can be influenced by external stressors. Cells can add small chemical modifications to genes, which may alter their activity. These modifications can help individuals adapt to stressful conditions, though their long-term effects remain largely unknown.

To investigate this, Dr. Connie Mulligan of the University of Florida collaborated with Dr. Rana Dajani of Hashemite University in Jordan and Dr. Catherine Panter-Brick of Yale University. Their study focused on three generations of Syrian families, comparing those who had experienced the Hama attack or the more recent Syrian civil war to those who had immigrated to Jordan before 1980 and thus avoided the conflicts.

Study Methodology and Findings

Dajani, a refugee’s daughter herself, built relationships with the Syrian refugee community in Jordan, enabling the collection of cheek swabs from 138 individuals across 48 families. The team analyzed DNA samples for epigenetic modifications and correlated these with exposure to violence.

The study revealed 14 distinct genetic sites modified in the grandchildren of Hama survivors, indicating that stress-induced epigenetic changes can be inherited. Additionally, 21 epigenetic modifications were identified in individuals who had directly experienced violence in Syria. Furthermore, those exposed to violence in utero exhibited signs of accelerated epigenetic aging, which could increase susceptibility to age-related diseases.

Implications for Public Health and Society

These findings suggest that violence-induced genetic changes may not be limited to war survivors but could also be relevant to other forms of trauma, including domestic abuse, sexual violence, and gun violence. Mulligan emphasizes the importance of recognizing and studying these effects to inform public health policies and interventions.

Although the precise consequences of these epigenetic changes remain uncertain, previous studies have linked stress-induced modifications to health risks such as diabetes and obesity. The study of Dutch famine survivors from World War II found similar genetic alterations in their descendants, further supporting the idea that stress can leave a lasting genetic imprint.

Resilience Amidst Trauma

Despite uncovering these long-term genetic effects, the researchers were equally struck by the resilience and perseverance of the families involved. Survivors and their descendants continue to build meaningful lives, preserve cultural traditions, and raise families despite the adversity they have faced.

“Amid all this violence, we can still celebrate their extraordinary resilience. They have persevered, and that perseverance is quite possibly a uniquely human trait,” Mulligan remarked.

This study, supported by the National Science Foundation, highlights not only the lasting biological scars of violence but also the enduring strength of those who survive it. As scientists continue to explore the epigenetic impact of trauma, their findings may pave the way for policies and interventions that promote healing and break cycles of intergenerational hardship.

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