SAN DIEGO — A new genetic study uses information from an unprecedented number of U.S. veterans to probe a particularly vexing question: Why does posttraumatic stress disorder affect some, but not others?
It is a particularly urgent question given that suicide rates are higher among veterans suffering from PTSD, which is estimated to affect between 11% and 20% of those who served in the military.
Recently published in the journal Nature Science by collaborating investigators at the University of California, San Diego and Yale University, the study is the first PTSD analysis to draw upon genetic information collected by the Million Veteran Program.
Created by the U.S. Department of Veterans Affairs, the voluntary initiative seeks to create a medical database large enough that researchers can see patterns of genetic variation capable of providing indispensable road maps for the future treatment of many diseases.
Though the program does not yet have its full sampling of 1 million records available, there is already enough data in place to allow the research team to study more than 165,000 veterans.
Using sophisticated computer modeling techniques, they were able to compare the genomes of those who experienced a key symptom of post-traumatic stress to those who did not.
Eight DNA locations
Common genetic differences were observed at eight different DNA locations among veterans who reported “re-experiencing” a PTSD symptom associated with nightmares and flashbacks that are sometimes triggered by events similar to those that were present when trauma first occurred.
Differences at three different chromosome locations were deemed to be most statistically significant and are thought to potentially affect the body’s hormone response to stress and, perhaps, to the function or structure of certain types of neurons in the brain.
Though mutations in these genes have previously been suspected to have something to do with PTSD susceptibility, science is increasingly finding it necessary to compare the genetic fingerprints of many, many real people in order to tease out which changes, among many possibilities, drive complex disorders such as PTSD.
Dr. Murray B. Stein, a UC San Diego psychiatry and family medicine professor who led the study with Dr. Joel Gelernter, a professor of genetics and neuroscience at Yale, was quick to note that this type of association study offers suggestions rather than clear answers.
But correlating genetic information on such a large scale, he said, provides the kind of signal in the noise that can help guide deeper investigations in the future.