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A new study from the Psychiatric Genomics Consortium provides the first molecular evidence that genetic influences play a role in the risk of getting post-traumatic stress disorder (PTSD) after traumatic experiences. The report extends previous findings that showed that there is some shared genetic overlap between PTSD and other mental disorders, such as schizophrenia. Interestingly, the new data also found that genetic risk for PTSD is strongest among women. Findings from the new study were published today in Molecular Psychiatry in an article entitled “Largest GWAS of PTSD (N=20,070) Yields Genetic Overlap with Schizophrenia and Sex Differences in Heritability.”

“We know from lots of data—from prisoners of war, people who have been in combat, and from rape victims—that many people exposed to even extreme traumatic events do not develop PTSD. Why is that?” asked senior study investigator Karestan Koenen, Ph.D., professor of psychiatric epidemiology at Harvard T.H. Chan School of Public Health and head of the Global Neuropsychiatric Genomics Initiative of the Stanley Center for Psychiatric Research at Broad Institute. “We believe that genetic variation is an important factor contributing to this risk or resilience.”

PTSD is a common and debilitating mental disorder that occurs after a traumatic event. Symptoms include re-experiencing the traumatic event, avoiding event-related stimuli, and chronic hyperarousal. In the U.S., one in nine women and one in twenty men will meet the criteria for a PTSD diagnosis at some point in their lives. The societal impact is large, including increased rates of suicide, hospitalization, and substance use.

The new genome-wide association study (GWAS) brings together data from more than 20,000 people participating in 11 multiethnic studies around the world. The new findings build a strong case for the role of genetics in PTSD, which had been previously documented on a smaller scale in studies of twins. Analysis of the data revealed that, among European American females, 29% of the risk for developing PTSD was influenced by genetic factors, which is comparable to that of other psychiatric disorders. In contrast, men's genetic risk for PTSD was substantially lower.

Additionally, the study investigators found strong evidence that people with a higher genetic risk for several mental disorders—including schizophrenia, and to a lesser extent bipolar and major depressive disorder—are also at higher genetic risk for developing PTSD after a traumatic event.

“PTSD may be one of the most preventable of psychiatric disorders,” concludes lead study investigator Laramie Duncan, Ph.D., instructor of psychiatry and behavioral sciences at Stanford University. “There are interventions effective in preventing PTSD shortly after a person experiences a traumatic event. But they are too resource intensive to give to everyone. Knowing more about people's genetic risk for PTSD may help clinicians target interventions more effectively, and help us understand the underlying biological mechanisms.”

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