Recent combat veterans who are diagnosed with post traumatic stress disorder have significantly smaller volume in an area of the brain critical for regulating fear and anxiety responses, according to research led by scientists at Duke University and the Durham VA Medical Center.
The finding, published Nov. 5, 2012, in the journal Archives of General Psychiatry, for the first time provides clear evidence that smaller amygdala volume is associated with PTSD, regardless of the severity of trauma. But it's not clear whether the physiological difference was caused by a traumatic event, or whether PTSD develops more readily in people who naturally have smaller amygdalas.
"Researchers found 20 years ago that there were changes in volume of the hippocampus associated with PTSD, but the amygdala is more relevant to the disorder," said Rajendra A. Morey, M.D., M.S., assistant professor at Duke and lead author of the study. Morey said studies in animals have established the amygdala's role in regulating fear, anxiety and stress responses, but its effect on human behavior is less well known.
"It's associated with how fear is processed, especially abnormal fear processing." Morey said. "So it makes sense to look at the structure of the amygdala."
The researchers enrolled 200 combat veterans who served in Iraq and Afghanistan after Sept. 11, 2001; half had PTSD and the other half had been exposed to trauma, but had not developed PTSD. Amygdala and hippocampus volumes were computed from MRI scans of all the participants.
The researchers found significant evidence that PTSD among study participants was associated with smaller volume in both the left and right amygdala, and confirmed previous studies linking the disorder to a smaller left hippocampus. The differences in brain volumes between the two groups were not due to the extent of depression, substance abuse, trauma load or PTSD severity – factors the researchers took into account in their statistical model.
The finding provides new insight into a condition that strikes nearly 14 percent of combat veterans serving in Iraq and Afghanistan, according to the Department of Veterans Affairs. PTSD is also estimated to afflict 6.8 percent of adults in the general population who have suffered abuse, crimes and other traumas over their lifetimes.
"The next step is to try to figure out whether a smaller amygdala is the consequence of a trauma, or a vulnerability that makes people get PTSD," Morey said.
He said the study demonstrated that amygdala volume does not appear to be affected by the severity, frequency or duration of trauma, indicating that such exposures do not cause the amygdala to shrink. As a result, it appears more likely that people with measurably smaller amygdala to begin with are susceptible to PTSD, but more studies are needed to make that determination.
Morey said he and colleagues are exploring that question, and are intrigued by evidence from their study that suggests people may have a propensity for developing PTSD based on inherently smaller amygdala volume.
"This is one piece in a bigger puzzle to understanding why some people develop PTSD and others do not," Morey said. "We are getting closer to that answer."
Duke University Medical Center: http://www.dukemednews.org
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
What’s scarier than a tyrannosaur? Three tyrannosaurs.
The timing of when a girl reaches puberty is controlled by hundreds of genes, say scientists.
After the world's most expensive salvage operation, the ill-fated Costa Concordia is being floated back to Genoa, where it will be chopped up for scrap metal
Hijacking how neurons of nematode worms are wired is the first step in an approach that could revolutionise our understanding of brains and consciousness
A Beverly Hills auction house has an unusual fossil for sale. It's not an ancient animal. It's something an ancient animal left behind — and it's very, very long.
Dog owners don't doubt that their pooch has feelings. But scientists aren't so sure. An experiment found that dogs act upset, dare we say jealous, when their owners ignore them for a stuffed animal.
Princeton University’s annual science art contest shines a light on the research world, adding a video element this year
Using mitochondrial replacement therapy to create embryos with DNA from three people could have serious consequences Continue reading...
Chinese and Australian scientists find pandas migrate long distances to maintain a balanced diet which helps them breed
On the morning of March 15, 2000, 17 beaked whales stranded themselves on beaches in the northern Bahamas. It was an terrible and extraordinary event: beaked whales are the world's deepest-diving mammals, and these creatures had spent most of their lives in deep undersea canyons.