A particular gene variation may play an important role in determining whether or not a soldier develops post-traumatic stress disorder (PTSD), according to new research at the National Institute of Mental Health (NIMH).
The genetic connection to PTSD is becoming increasingly clear, along with the complex relationship between hormones such as serotonin and PTSD. Many studies in civilians have suggested a link between this risk gene and PTSD after a traumatic event.
For the study, researchers tracked over 1,000 Israeli soldiers from 2008 to 2010 and used computerized tests to measure the soldiers’ levels of “threat bias.” Threat bias was determined by measuring the difference in time it took a soldier to respond to threatening words such as “death” compared to more neutral words like “door.”
A link between the “combat gene” and PTSD was found in those soldiers experiencing high levels of combat and pre-existing levels of high threat vigilance. Soldiers with PTSD symptoms before deployment were at greater risk for PTSD after being deployed.
“Soldiers preoccupied with threat at the time of enlistment or with avoiding it just before deployment were more likely to develop post-traumatic stress disorder (PTSD),” said the researchers.
The combat gene may be an adaptation for high stress, high threat situations, where extreme levels of vigilance offer greater safety and awareness of surroundings. The anxiety and alertness created by the less efficient form of the gene offers little or no benefit in normal life.
Furthermore, soldiers who did not graduate from high school were found to be at greater risk for post-deployment PTSD.
On the other hand, soldiers with a high efficiency form of the serotonin transporter gene were better able to adapt to combat situations and showed no association with PTSD symptoms.
Serotonin is a neurotransmitter that plays an important role in the regulation of learning, mood, sleep and vasoconstriction (constriction of blood vessels).
It is commonly thought that a lack of serotonin in the brain is a potential cause of depression. Drugs called selective serotonin-reuptake inhibitors (SSRI) are often prescribed for both the treatment of depression and for the treatment of PTSD.
The study of Israeli soldiers shows that it may be possible to use computerized testing to identify soldiers at risk of PTSD by measuring their threat bias and then testing for the “combat gene.”