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The Yale Study
Researchers have long believed that an individual's response to trauma - such as war, violent attack or natural disasters - is dependent not only on the intensity of the experience but also on a complex interplay of genes and environmental factors such as the person's life experiences. Now there is strong scientific backing for the biological part of this equation.
In November of 2009, researchers at the Yale School of Medicine were the first to discover that there might be a post-traumatic stress disorder (PTSD) genetic link. They analyzed genetic data from 1,200 individuals who had gone through a trauma, looking specifically at the serotonin transporter protein gene on chromosome 17. This gene is responsible for producing a protein to reabsorb serotonin - the chemical that affects a person's mood, specifically anger and aggression - into neurons. The researchers found that having the short allele of the gene makes the person produce less serotonin transporter protein, which in turn makes them more likely to develop PTSD
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The Miller Study
Then came the Miller study, performed at the University of Miami Miller School of Medicine and published in the prestigious journal Nature. Through this study researchers tried to identify a gene that would predispose some people to PTSD.
To do this, researchers collected blood samples from more than 1,200 patients in an Atlanta emergency room who had undergone severe trauma. They then analyzed the samples based on which patients went on to develop PTSD and which did not. They traced the difference to the PACAP (pituitary adenylate cyclase polypeptide) gene, as well as the corresponding gene receptor PAC 1 - both of which are partially responsible for regulating a person's response to cellular stress. People who developed PTSD had an over-expressed PACAP gene, possibly due to a slight variant of the gene that is more sensitive to a mixture of estrogen and stress. The gene had a strong association with hyperarousal, intrusive memories and avoidant behavior, which are the three main symptoms of PTSD.
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Why it Matters
You may wonder why it matters whether a PTSD genetic link exists. The main reason is that treating someone who is not likely to develop PTSD can backfire. Several people may go through a traumatic event, with only a small percentage of them being at risk for PTSD. In fact, only eight percent of Americans have had a PTSD diagnosis, although between 40 and 70 percent have gone through a trauma. Although psychological intervention is important in helping people who have been diagnosed with PTSD, it can be counterproductive -- and actually harmful -- to those who would otherwise recover normally.
These studies can lay the groundwork for tests that will enable doctors to determine which patients are predisposed to developing PTSD. In that way, only patients who are likely to develop the disorder will be treated. The studies may also help researchers to develop better treatments for people who are in the early stages of this mental health condition.
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Yale Daily News. "Yalies find genetic link to PTSD. http://www.yaledailynews.com/news/2009/nov/04/yalies-find-genetic-link-to-ptsd/
University of Miami Miller School of Medicine. "UM Researchers Identify Genetic Link to Post-Traumatic Stress Disorder." http://med.miami.edu/news/um-researchers-identify-genetic-link-to-post-traumatic-stress-disorder
Psych Central. "Gene May Be Tied to Post-Traumatic Stress Disorder (PTSD)." http://psychcentral.com/news/2011/03/01/gene-may-be-tied-to-post-traumatic-stress-disorder-ptsd/23890.html
CNN Health. "PTSD in Women May Have Genetic Link." http://thechart.blogs.cnn.com/2011/02/25/ptsd-in-women-may-have-genetic-link/