FORT DETRICK, Md. –
Researchers at the U.S. Army Research Institute of Environmental Medicine may have found a genetic marker for adaptability to stress – a discovery that could potentially open the door to new methods for helping warfighters manage stress more effectively and perhaps even to therapies for treating stress-induced trauma such as post-traumatic stress disorder.
A study conducted by a team from USARIEM’s Military Nutrition Division found that test subjects who scored highly on a self-evaluation designed to assess resilience were statistically more likely to have a particular variation in the gene that controls the brain’s ability to uptake serotonin, the so-called “feel-good hormone” that among other things regulates the sense of emotional well-being.
The discovery was the result of research conducted by the USARIEM team over the course of several months as they followed Special Forces candidates through the grueling Survival, Evasion, Resistance, and Escape course at the U.S. Army John F. Kennedy Special Warfare Center and School at Camp Mackall, in North Carolina. “SERE school is really an optimal place to study the effects of acute stress,” says Dr. Harris Lieberman, the principal investigator on the study. “In the final phase of the training, students are held in a mock prisoner-of-war camp, in which they are exposed to, and must try to resist, the stressors of captivity.”
As reported in a paper coauthored by Lieberman in the journal Anxiety, Stress, & Coping, the study followed a cohort of 73 officers and enlisted personnel as they progressed through the three-week SERE course. At the outset of the course, the researchers collected baseline information by giving study participants a battery of three questionnaires that assessed their mood state and stress adaptability, and took saliva samples to serve as baseline measures of their cortisol – the most widely accepted biomarker of a body’s activated stress response. At the end of the three-week course, the researchers repeated the process to compare the results. Lieberman’s team also collected blood samples from each of the study participants for genomic analysis, looking for the presence of genes that are commonly associated with the body’s response to stress.
Lieberman found that participants’ cortisol levels during the captivity phase of the course – the most intense period of the training – were on average nearly 10 times higher than their baseline levels. However, despite having endured extreme levels of stress, a number of volunteers actually reported an improvement in their responses to questions such as “I am able to adapt when changes occur,” “Under pressure, I stay focused and think clearly,” and “I am not easily discouraged by failure” following the completion of the SERE course. When he examined the genomic data for those survey respondents, Lieberman found that they correlated strongly with the presence of a particular, and somewhat rare, variant of the gene that regulates serotonin in the brain called SNP rs4251417.
“Our study suggests an association between SNP rs4251417 and a positive change in resilience in individuals who are exposed to high stress,” says Lieberman. “We consider the study to be preliminary, but our findings align with those of several other studies and suggest some interesting possibilities for future research in support of the Special Forces’ interest in identifying the factors that predict the career success of soldiers who go into Special Forces training and then on to active duty.”
Identifying physiological metrics that predict tolerance and resilience to military relevant stressors is one of the research areas that USARIEM’s Military Nutrition Division focuses on as part of its mission to provide the DOD with sound biomedical underpinnings for a wide range of policies and programs that ensure warfighter readiness, optimal performance, and lethality. Lieberman’s study is part of an ongoing partnership with Army Special Forces to identify the physical, demographic, psychological, and physiological predictors of success in the demanding training and operational environments in which they operate. Lieberman’s team has been collecting a wealth of data on candidates as they move through the Special Forces’ rigorous training program for over a decade.
One intriguing – and unexpected – finding was that the percentage of Special Forces soldiers in the study who possess the SNP rs4251417 variant was significantly higher than the percentage of the general population who have it. Scientists have found that the variant is only found in 9% of people, but 15% of the study volunteers had it. While this finding could indicate that people with greater stress resilience may be inclined to pursue high-stress occupations, more studies will be required to rule out the possibility that it was merely coincidental.
Lieberman says that the results of the preliminary study suggest the potential for developing tools and techniques to help warfighters better manage stress and recover more quickly from stress-induced psychological traumas.
“When you understand the mechanisms that are responsible for stressing individuals and impairing their functional ability, it suggests the potential of therapeutic and behavioral interventions that take into consideration the underlying causes of the individuals’ intense and unhelpful stress levels,” says Lieberman. “We may be able to improve therapeutic options for individuals who are at greater risk of experiencing a psychiatric disorder through exposure to high levels of stress that they can't accommodate.”