This is the first time that epigenetic changes in the blood have been linked to the development of PTSD symptoms. It has long been known that some soldiers develop PTSD symptoms after deployment. This research project focused on them. The researchers took two blood samples from a few hundred Dutch soldiers: one just before they took part in the ISAF mission in Afghanistan, and another six months after they returned. The scientists investigated these samples in the laboratory to look for epigenetic changes in DNA. They found that soldiers who developed PTSD symptoms showed fewer epigenetic changes in specific sites of their DNA. These findings from Dutch soldiers are supported by research that found the same result in a group of American marines who had also been deployed to Afghanistan.

Many people are exposed to traumatic events and can suffer great psychological consequences. But that exposure does not have the same psychological effect on everyone. ‘It is important to understand why the impact of traumatic experiences has varying effects on the psychological state of soldiers and other risk groups. Our research contributes to this understanding. Even though our findings only explain a small portion of PTSD symptoms, they are an important first step in unravelling the biological mechanisms involved’, explains Prof Bart Rutten, professor of the Neuroscience of Mental Disorders at Maastricht University.

Epigenetic changes refer to the phenomenon by which genes under pressure from environmental factors can be turned ‘on’ or ‘off’. Thus, the function of a gene changes without any change to its code. Imagine this like the performance of exactly the same score by different musicians: the piece is the same, but the music sounds different. Two people can be genetically identical but vary epigenetically. This research shows that war trauma has an important influence on that mechanism.

Dr Marco Boks, psychiatrist and researcher at University Medical Center Utrecht: ‘This is a unique study that could not have been done without the efforts of large groups of soldiers and researchers. The research builds a beautiful bridge between emotional experiences and the molecular sciences.’

‘This research is a first step in understanding the complex biological process around sensitivity to the impact of a traumatic experience’, says Prof Eric Vermetten, head of the Military Research Centre for Mental Health (Militaire Geestelijke Gezondheid van Defensie). ‘This is interesting research, made possible by the Dutch armed forces. The results may eventually help in the earlier identification of people who are vulnerable to PTSD.’