Memory Gene May Fuel PTSD
A vivid memory can be an asset if you're studying for an exam or trying to recall the details of a conversation, but that aptitude may backfire when it comes to forming long-term responses to emotional trauma.In a new study, Swiss researchers have found that a certain gene associated with a good memory—and in particular, the ability to remember emotionally charged images—is also linked to an increased risk of post-traumatic stress disorder (PTSD) among survivors of the 1994 genocide in Rwanda. "We are very confident that the gene is associated with the risk for PTSD, at least in the Rwandan population," says lead author Andreas Papassotiropoulos, MD, a professor of molecular neuroscience at the University of Basel, in Switzerland. Although the findings suggest that memory and post-traumatic stress share a genetic basis, it's not clear exactly how the gene or the sharpness of a person's memory might increase the risk of PTSD, which is characterized by sudden, painful flashbacks of traumatic events.
"Some people have very, very detailed visual memories," says Keith A. Young, PhD, co-director of neuropsychiatry research at the Texas A&M Health Science Center College of Medicine, in Temple. "Perhaps there's something about that detailed kind of visual memory that makes it easier for you to have a flashback. That's one explanation."
The study, published in the Proceedings of the National Academy of Sciences, had two phases.
First, Dr. Papassotiropoulos and his colleagues analyzed the DNA of more than 700 mentally healthy Swiss adults, and cross-referenced the results with each individual's performance on a memory test. The ability to recall photographs 10 minutes after seeing them was associated with a certain gene variation that is believed to play a role in so-called emotional memory.
The researchers backed up this finding by repeating the memory test in a different group of about 400 Swiss adults. Using a type of brain scan known as functional magnetic resonance imaging, they found that the same gene variation was associated with certain patterns of brain activity known to be involved in storing memories.
The second phase of the study took place in Uganda, in a refugee camp that houses survivors of the Rwandan genocide. In 2006 and 2007, a group of about 350 camp residents agreed to provide DNA samples and undergo interviews to assess whether they had symptoms of PTSD.
All of the volunteers had lived through horrific trauma, such as rape and beatings, but only about 40% were found to have active PTSD. As the researchers suspected, the same gene variant identified in the Swiss participants was associated with an increased risk of PTSD, as well as with an increased risk of flashbacks with or without full-blown PTSD.
The study leaves several important questions unanswered. The researchers don't yet know how the gene, which is involved in many different processes at the cellular level, is related to memory. And it's too soon to tell whether a better understanding of the genes that contribute to memory and PTSD will improve prevention or treatment of the disorder.
Young, who was not involved in the study, cautions that the data is still very preliminary. "There's nothing here that says this is going to be a gene with a big effect size on PTSD," says Young, who studies the genetic and neurological underpinnings of PTSD at the Center of Excellence for Research on Returning War Veterans, a facility in Waco, Texas, sponsored by the Department of Veterans Affairs.
In addition, it's not clear if the association seen in the study can be extrapolated to other populations, such as military veterans. Although some aspects of PTSD tend to be consistent from case to case, the type of psychological trauma a person experiences can influence how the disorder develops, Papassotiropoulos says.
The fact that the gene variant in the study was associated with memory in two genetically different populations, and in people with PTSD as well as mentally healthy adults, suggests that the findings may be broadly applicable. However, further studies will be needed to confirm that, Dr. Papassotiropoulos says.
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