Rwandan Genocide Survivors Offer Insights Into PTSD

/ Author:  / Reviewed by: Joseph V. Madia, MD

The 1994 genocide in Rwanda resulted in the mass killing of up to 1 million people over the course of about 100 days. There can be no doubt or surprise then that some of the survivors developed posttraumatic stress disorder (PTSD), an anxiety disorder that can develop after witnessing or experiencing a traumatizing event, such as abuse, war or natural disaster.
However, even under stress as extreme as genocide, not all individuals develop PTSD. Why is it that some people do and some don't? A new study published in Biological Psychiatry was designed to address that question.

The clues may come from molecular genetics. Scientists already know that, in general, the more traumatic events a person experiences, called traumatic load, the higher the likelihood of developing PTSD. In this new study, Iris-Tatjana Kolassa and her colleagues show that genetic factors influence this relationship.

They studied 424 Rwandan genocide survivors, some with and some without PTSD. As expected, they found those survivors with higher traumatic load had a higher prevalence of lifetime PTSD, a dose-response relationship. But importantly, they also found the Val158Met polymorphism of the gene encoding the enzyme catechol-O-methyltransferase (COMT) plays a role in this relationship.

Individuals homozygous for the Met allele of this COMT polymorphism have substantially lower activity of this enzyme. Lower COMT activity would be expected to produce higher levels of norepinephrine and dopamine, neurotransmitters released during stress. Rwandan survivors with at least one Val allele in this gene showed the typical dose-response relationship between trauma severity and PTSD risk, but those individuals homozygous for the Met allele exhibited a high risk for PTSD independent of the severity of traumatic load.

In other words, people who, due to their genotype, were more likely to inactivate the stress neurotransmitters were somewhat protected from developing stress-related problems relative to people who were less able to metabolize the transmitters.

Dr. John Krystal, editor of Biological Psychiatry, commented, "We hope that molecular genetics will help us to identify those who are most resilient so that we can learn about ways that people cope with stress at a psychological, behavioral and biological level. We also would like a biological test to help us to identify people who are most vulnerable to the negative effects of stress so that we could target supportive services to these people." This study is another step in that direction.

Dr. Iris-Tatjana Kolassa cautions that many technical and clinical questions remain open in attempting to develop molecular genetic tests that predict patterns of stress response. But she acknowledged human genetics could someday play a role in preventing and treating PTSD.

Maureen Hunter

Reviewed by: 
Review Date: 
September 20, 2010