Through a combination of genetic and psychological testing, Tel Aviv University researchers have identified factors that reduce the risk among combat soldiers of developing post-traumatic stress disorder (PTSD). The study was conducted on 1,100 new Israel Defense Forces (IDF) infantry recruits.
The important discovery has just been published in the February 13th issue of the ITALJournal of the American Medical Association (JAMA) END ITAL by TAU’s School of Psychological Sciences Prof. Yair Bar-Haim and doctoral student Ilan Wald. Their research was conducted in collaboration with the IDF, the US National Institutes of Mental Health and New York’s Mount Sinai School of Medicine.
Soldiers have a high probability of experiencing traumatic events, explained Bar-Haim, so a susceptible subgroup is practically bound to develop the disorder. However, the onset of PTSD -- a severe anxiety disorder that can develop after exposure to any traumatic event and includes nightmares, flashbacks, sleep problems, hypervigilance and other symptoms -- is unpredictable.
Because it depends on the unforeseeable occurrence of traumatic events, it is difficult to identify preventative or causative factors, the researchers said. Scientists typically study people who have already developed PTSD rather than look at people who have not yet developed PTSD but may be at risk of experiencing psychological trauma. As soldiers have a high probability of experiencing traumatic events, members of a susceptible subgroup are more likely than others to develop the disorder.
The TAU-led researchers discovered that excessive vigilance from threats -- a behavior typically associated with elevated anxiety in everyday life -- is a normal response in soldiers during combat deployment. In combat, they found, those soldiers who avoided threats were more likely to develop PTSD as a result of traumatic experiences.
Through "attention-bias modification training" – which trains participants to direct their attention either towards or away from threatening stimuli – soldiers were able to learn to increase their vigilance towards threats before they were deployed, possibly reducing their risk for PTSD. Bar-Haim noted that this discovery could prove valuable in preventing PTSD in groups that are more likely to be exposed to traumatic situations.
To explore the causative factors of PTSD, Bar-Haim and his colleagues designed a study of 1,100 new infantry recruits, each of whom underwent testing first at the time of recruitment, again after basic training and finally six months into their deployment in a conflict zone.
Several major vulnerability and resilience factors were measured -- self-reported symptoms of anxiety, depression, and PTSD; threat-related attention bias; combat exposure; and genetic markers that indicate a tendency towards anxiety.
The researchers noticed that where computer-based testing revealed a strong vigilance towards threats during deployment, the soldier was much less likely to develop PTSD. That discovery corresponded to significant genetic findings about the serotonin transporter gene, which plays a key role in the control of serotonin availability in the brain and modulates important psychological functions such as mood, appetite, and sleep.
The gene has three variants -- short/short, short/long and long/long. The short/short variant of the gene is associated with enhanced threat vigilance and a higher incidence of anxiety and depression in everyday conditions. But in war zones, soldiers who carried the short/short variant of the gene were actually at an advantage, since their attuned attention towards threat protected them from developing PTSD in traumatic situations.
In Israel, which has gone through many decades and terror campaigns, PTSD symptoms affect about six to seven percent of the general population. For foreign soldiers serving in active war zones like Iraq or Afghanistan, the rate is much higher and could reach up to 20%, reported Bar-Haim.
Bar-Haim thanked the IDF and US Army for recognizing the importance of his research and therefore participated. "They are on the front line of science in trying to understand risk and resilience factors," he said.
Identifying this protective factor is a first step towards preventative treatment, the TAU professor said. Teaching soldiers to be more sensitive to threats prior to deployment could reduce the overall risk of developing PTSD. The researchers are currently developing a study that will test different preventative treatment options and hope to have results in the next few years.