Study findings released on Wednesday by the National Institute of Mental Health (NIMH) suggest that a previously described genetic variation may play a critical role in whether or not a soldier develops post-traumatic stress disorder (PTSD). The study followed more than 1,000 Israeli soldiers from 2008 to 2010 and used computerized test to measure their levels of "threat bias."
Threat bias was measured by the soldier's timed response to certain words such as "death" versus more benign words such as "door." Changes in response times indicated a reaction to the "threat" words differently than to the low stress words. "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)..."
The study found that soldiers with a variant of the serotonin transporter gene that is less efficient in its activity and high threat vigilance were better adapted to combat situations. The high-efficiency form of the gene showed no association with PTSD symptoms. The association between the gene and PTSD was found only in those soldiers experiencing high levels of combat and pre-existing levels of high threat vigilance.
The "combat gene" may be an adaptation for high stress, high threat situations, where unusual levels of vigilance provide greater safety and situational awareness. The anxiety and vigilance resulting from the less efficient gene provides little or no benefit in normal life. The study found that pre-deployment PTSD symptoms were an indicator of a greater post-deployment risk of PTSD. Soldiers who failed to graduate high school were also found to be at greater risk for post-deployment PTSD.
Serotonin is a hormone that permits nerves to send messages to other nerves. It is also a substance that can cause blood vessels to constrict. The National Cancer Institute suggests that a lack of serotonin in the brain is a potential cause of depression. Drugs called selective serotonin-reuptake inhibitors (SSRI) are widely prescribed for both the treatment of depression and for the treatment of PTSD .
Many studies in civilians have suggested a connection between this "risk gene" and PTSD after a traumatic event. The genetic connection to PTSD is becoming increasingly clear, along with the complex relationship between hormones such as serotonin and PTSD. The study of Israeli soldiers suggests that it may be possible to use computerized testing to identify those at risk of post-deployment PTSD by measuring their threat bias and then testing for the "combat gene."
- Mental Health