The traumatic experiences of the 1994 Genocide of the Tutsi in Rwanda may have caused changes in the DNA of victims and the children born by women who were pregnant then.

A study published in Epigenomics on January 10 found that the trauma was associated with chemical modifications to the DNA of genocide-exposed women and their offspring.

The genocide, which led to the deaths of about one million people, most of them Tutsis, left a public health burden of post-traumatic stress (PTSD) and other mental health disorders in Rwanda.

In this first of its kind study, scientists have been investigating the genomes of Tutsi women who were pregnant and living in Rwanda at the time of the genocide and their offspring versus those of Tutsi women pregnant at the same time who were living in other parts of the world.

The study conducted by the University of South Florida in collaboration with the University of Rwanda found that many modifications occurred in the gene that contribute to the risk of mental disorders such as PTSD and depression. These findings suggest that, unlike gene mutations, these chemical epigenetics’ modifications can have a rapid response to trauma across generations.

Epigenetics is the study of how behaviour and environment can cause changes that affect how genes work, says the Centres for Disease Control and Prevention. Unlike genetic changes, epigenetic changes are reversible and do not change your DNA sequence, but can change how your body reads a DNA sequence.

Prof Monica Uddin of the College of Public Health, University of South Florida explained that chemical modifications made to DNA can happen in a shorter time frame than is needed for changes to the underlying DNA sequence of genes.

“Our study found that prenatal genocide exposure was associated with an epigenetic pattern suggestive of reduced gene function in offspring,” she said.

The team, came to their conclusion following the review of DNA from blood samples from 59 individuals — about half exposed personally to genocide-related trauma such as rape, evading capture, witnessing murder or a serious attack with a weapon and seeing dead and mutilated bodies or exposed in utero to the genocide.

“The Rwandan people who are in this study and community as a whole really want to know what happened to them because there’s a lot of PTSD and other mental health disorders in Rwanda and people want answers as to why they’re experiencing these feelings and having these issues,” said Prof Derek Wildman of University of South Florida.

While this study looks specifically at the impact of the 1994 genocide, it supports previous studies that show that what occurs to a foetus during pregnancy can have long-term impacts hence the need to protect the safety and emotional and psychological wellbeing of pregnant women.

The researchers noted that individuals who were in utero during the genocide are starting to have children of their own and they hope to soon look at whether or not that trauma has had an epigenetic impact on the third generation.

The pioneering study is part of a larger consortium, the Human, Heredity & Health in Africa (H3) funded by the National Institutes of Health, to empower African scientists in genomics. It is meant to increase their independence and ability to build the infrastructure needed to enhance genetic studies across the continent, and ultimately better capture data on the human genome across the world.