Violence changes human genes for generations, study finds

The impact of maternal trauma extends beyond a single generation, influencing the health of children and grandchildren through changes in gene expression.

Scientists believe this transmission occurs through epigenetic modifications—small chemical changes to DNA that regulate gene activity. One of the most studied modifications, DNA methylation, alters how genes are turned on or off, potentially affecting health outcomes for decades.

The Developmental Origins of Health and Disease (DOHaD) hypothesis suggests that early-life adversity, such as low birth weight and poor living conditions, increases the risk of chronic diseases in adulthood.

The developing fetus adapts to stressors in the womb by adjusting biological processes, but these adaptations can become harmful later in life. Factors like poor nutrition, exposure to toxins, and psychosocial stress, including trauma and violence, can permanently shape a child’s response to stress and disease risk.

Studies show that maternal stress affects a fetus by altering the hypothalamic-pituitary-adrenal (HPA) axis, which regulates the body's response to stress. These changes influence glucocorticoid metabolism, affecting immune function, metabolism, and mental health.

However, the exact molecular mechanisms that preserve these changes across generations remain unclear. Researchers propose that epigenetic modifications provide a fast, flexible response to environmental stressors, with some modifications potentially being passed down to future generations.

The idea that stress and trauma can be inherited has been supported by research in animals, but evidence in humans has remained scarce.

A groundbreaking study now provides new insights, revealing that the trauma of war can leave an imprint on the genes of the descendants of those affected. The research, published in Scientific Reports, examines three generations of Syrian families, some of whom experienced extreme violence during the Hama massacre in 1982 and the more recent Syrian civil war.

Led by Connie Mulligan, Ph.D., an anthropologist and geneticist at the University of Florida, the study sought to determine whether trauma left detectable marks on the DNA of those who had never directly experienced it.

Working with Rana Dajani, Ph.D., a molecular biologist at Hashemite University in Jordan, and Yale anthropologist Catherine Panter-Brick, Ph.D., the team analyzed DNA samples from 138 people across 48 families. Some families had lived through the Hama siege, others had fled the recent civil war, and a control group had immigrated to Jordan before 1980, avoiding the conflicts.

Dajani, herself the daughter of refugees, worked closely with the families to build trust and gather DNA samples. "The families want their story told. They want their experiences heard," Mulligan explained.

The study collected DNA through cheek swabs from grandmothers, mothers, and children, allowing researchers to compare epigenetic differences across generations.

The researchers identified 14 regions in the genome that showed epigenetic modifications in the grandchildren of Hama survivors. These chemical changes likely resulted from their grandmothers' experiences of violence during pregnancy. Additionally, 21 regions were altered in those directly exposed to war, reinforcing the idea that extreme stress leaves a biological signature.

One of the most striking findings was that people exposed to violence while in the womb exhibited signs of accelerated epigenetic aging. This phenomenon, which refers to biological aging at a faster rate than expected, has been linked to an increased risk of diseases such as diabetes and cardiovascular conditions later in life.

A similar effect was seen in studies of Dutch famine survivors from World War II, whose offspring showed epigenetic changes associated with metabolic diseases.

The persistence of these markers suggests that stress-induced genetic modifications could be a shared biological response across human populations. "We think our work is relevant to many forms of violence, not just refugees. Domestic violence, sexual violence, gun violence—these all leave lasting biological imprints that we need to study and take more seriously," Mulligan said.

While scientists still do not fully understand the long-term health effects of these epigenetic changes, evidence suggests they could contribute to cycles of trauma and disease.

The findings may explain why intergenerational patterns of poverty, abuse, and mental health disorders persist despite efforts to break them. If stress-induced epigenetic changes impact future generations, public health interventions must consider how trauma affects families on a biological level.

Some researchers believe that a few of these modifications may have evolved as protective mechanisms, helping individuals adapt to hostile environments. However, in modern society, these adaptations could become maladaptive, increasing susceptibility to mental health disorders and chronic diseases.

Despite the sobering implications, the study also highlights the resilience of those affected. "In the midst of all this violence, we can still celebrate their extraordinary resilience. They are living fulfilling, productive lives, having kids, carrying on traditions. That perseverance is quite possibly a uniquely human trait," Mulligan said.

This research underscores the importance of addressing trauma not just as a psychological or social issue, but as a biological one. Policymakers, healthcare providers, and researchers must recognize the lasting impact of violence and work to prevent its transmission to future generations.

By understanding how trauma affects the body at a genetic level, we can develop better strategies to support those who have endured extreme stress and break the cycle of inherited trauma.

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