Researchers have linked two gene variants to the development of post-traumatic stress disorder (PTSD). The findings, published in the Journal of Affective Disorders, may help explain why some people develop PTSD after a traumatic experience while others do not.
“Many people suffer with post-traumatic stress disorder after surviving a life-threatening ordeal like war, rape, or a natural disaster,” said lead author and psychiatrist Dr. Armen Goenjian at the Semel Institute for Neuroscience and Human Behavior at the University of California, Los Angeles (UCLA).
“But not everyone who experiences trauma suffers from PTSD. We investigated whether PTSD has genetic underpinnings that make some people more vulnerable to the syndrome than others.”
In 1988, Goenjian and his colleagues helped establish a pair of psychiatric clinics in Spitak, Armenia, after a 6.8 magnitude earthquake devastated the country, killing more than 25,000 Armenians, two-thirds of them children.
There he continued to treat the earthquake survivors for 21 years. The victims agreed to allow their blood samples to be sent to UCLA, where the researchers combed the DNA of 200 individuals for genetic clues to psychiatric vulnerability.
The team found that PTSD was more common in survivors who carried two gene variants associated with depression. They focused on two genes in particular — COMT and TPH-2 — that play an important role in brain function.
COMT is an enzyme that breaks down dopamine, a neurotransmitter that controls the brain’s reward and pleasure centers, and helps regulate mood, thinking, attention, and behavior. Too much or too little dopamine is an aspect of several neurological and psychological disorders.
TPH-2 regulates the production of serotonin, a brain hormone that helps control mood, sleep and alertness — all of which are disrupted in PTSD
“We found a significant association between variants of COMT and TPH-2 with PTSD symptoms, suggesting that these genes contribute to the onset and persistence of the disorder,” said Goenjian. “Our results indicate that people who carry these genetic variants may be at higher risk of developing PTSD.”
The researchers used the most recent PTSD criteria from the American Psychiatric Association to measure the role these genes play in a person’s risk for PTSD. The new criteria increased estimates of a person’s predisposition for PTSD to 60 percent; estimates based on older criteria reached only 41 percent.
“Assessments of patients based upon the latest diagnostic criteria may boost the field’s chances of finding new genetic markers for PTSD,” said Goenjian. “We hope our findings will lead to molecular methods for screening people at risk for this disorder and identify new drug therapies for prevention and treatment.”
Still, noted Goenjian, PTSD is likely caused by several genes, and studies should be continued to find more of the genes involved.
“A diagnostic tool based upon PTSD-linked genes would greatly help us in identifying people who are at high risk for developing the disorder,” Goenjian said.
“Our findings may also help scientists uncover more refined treatments, such as gene therapy or new drugs that regulate the chemicals associated with PTSD symptoms.”