Post-traumatic stress disorder (PTSD) is a mental disorder that can occur after exposure to extreme events, such as military conflicts or violent attacks. It is the only mental disorder that requires the presence of an external event for a positive diagnosis. Symptoms of PTSD include:
- Uncontrollable intrusive memories of the event
- Avoid places and things that have reminders of what happened
- Increased irritability, restlessness and negative thoughts about yourself
These symptoms can be so severe that they interfere with normal activities such as work, school, or family relationships. The prevalence of violence in large cities suggests that many people are experiencing traumatic events; However, only a fraction of those who survive trauma go on to develop PTSD. Estimates of the prevalence of PTSD in the general population are around 10 percent, which means that 90 percent of people who experience traumatic events will recover from the initial stress reaction. This statistic alone shows that some people are more vulnerable to trauma and others are more resilient.
The Grady Trauma Project
There are many factors that contribute to this vulnerability, but genes are one way some people are biologically predisposed to PTSD. In this way, PTSD provides an ideal context in which to study nature (genes) and nurture (extreme environmental influences) in mental illness. Twin studies have long shown that PTSD is heritable, but identifying specific risk genotypes has been difficult because such research requires DNA from large numbers of people.
Our recent research at the Grady Trauma Project, where we interview and collect saliva samples from thousands of people from inner-city Atlanta, has revealed several genetic markers of risk. Two of these genes, FKBP5 and ADCYAP1R1 are involved in the hormonal stress response and are associated with changes in the brain that regulate feelings of fear. Polymorphism (ie mutation) in FKBP5 gene associated with risk or resilience for PTSD.
Specifically, individuals with a stable genotype do not show increased PTSD symptoms, even if they have experienced multiple instances of childhood abuse. Polymorphisms in the second gene, ADCYAP1R1, The risk appears to be increased in women, but not in men. This particular gene responds to the cyclical levels of the female hormone estrogen, so between puberty and menopause, women are more vulnerable to PTSD. Studies have shown that women are twice as likely to develop PTSD as men. At least part of this discrepancy stems from female biology.
Iterative interactions and environmental factor solutions
Understanding the genetic and biological basis of vulnerability will allow for better medical procedures in the future; Ideally, individuals with multiple gene polymorphisms would receive treatment. However, it should be remembered that a person’s genotype determines not only his fate. Although a single gene cannot determine whether someone will get PTSD, mutated genes can present an increased risk.
In addition, there are many factors that can counteract this genetic risk and protect the individual from its effects even if an injury occurs. One of these factors is a supportive social network in the aftermath of trauma. Having friends and family to provide emotional and physical support goes a long way to overcoming the effects of a traumatic experience. Another factor of resilience is optimism and humor. Although it can be difficult to see after a traumatic experience, if a person is able to find and appreciate it, they are less likely to develop PTSD, even if they were born with risk genes.
