Natural disaster, violent crime and war are traumatic experiences for anyone to live through, yet some people recover quickly from these events while others struggle with the flashbacks and hypervigilance that characterize posttraumatic stress disorder (PTSD). Why?
Scientists say they have pinpointed certain genetic changes that may make some people more vulnerable to PTSD than others. The finding could one day make it possible to screen people for increased risk of developing the disorder.
Working with several generations of 12 families who survived the devastating Spitak earthquake in Armenia in 1988, Dr. Armen Goenjian and his colleagues at the University of California, Los Angeles, found that variations in genes that code for the brain chemical serotonin can affect how profoundly people are affected by trauma.
Serotonin is implicated in a number of mood-related disorders, including depression and anxiety. The neurotransmitter helps regulate sleep, mood and feelings of satisfaction and satiety, and doctors often prescribe medications that increase the amount of serotonin available in the brain to treat both depression and anxiety.
Because PTSD often occurs together with depression, Goenjian wondered whether serotonin-regulating genes might also be involved in PTSD. To find out, he took samples from the inner cheek tissue of 200 adults who survived the Armenian earthquake and conducted genomic analyses on three specific genes that regulate serotonin production.
In his previous work on potential genetic contributors to PTSD, Goenjian reported that about 40% of vulnerability to the mental disorder was inherited. In the current study, he isolated two possible variations of genes that code for an enzyme involved in serotonin production that could contribute to this generational propensity to PTSD. Together, the gene changes may account for 7% to 8% of the variance in severity of PTSD symptoms.
Goenjian is under no illusion that he’s found the primary genetic driver behind PTSD; it’s likely that the disorder is the result of a combination of multiple genetic variants. But, he says, “we’re pleased to have it. The next step is to pursue this finding in a larger population and probably other ethnic and racial groups, and to pursue other genes also.”
Still, the serotonin-related genes do provide a promising avenue for developing a way to screen people for increased risk of developing PTSD, and possibly to protect them from situations where they might experience severe emotional and physical trauma. “If someone has a vulnerability to developing PTSD, then we might be careful in assigning them to a task, such as going to a high combat zone where he might be exposing himself to a situation where he could be at risk of developing [the disorder],” says Goenjian. The findings could also help researchers create PTSD treatments that address changes in serotonin and help people who are more vulnerable to traumatic experiences recover from them more quickly.