Amygdala Volume Associated with Combat Veterans’ PTSD
DURHAM, NC — Combat veterans with post traumatic stress disorder (PTSD) tend to have significantly smaller volume in an area of the brain critical for regulating fear and anxiety responses, according to a new study from Durham, NC, VA Medical Center and Duke University.
The study, published last month in the journal Archives of General Psychiatry is the first to provide solid evidence that smaller amygdala volume is associated with PTSD, regardless of the severity of trauma. What remains unresolved, however, is whether the physiological difference was caused by a traumatic event or whether PTSD develops more readily in people who naturally have smaller amygdalas.1
“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 lead author Rajendra A. Morey, MD, MS. “It’s associated with how fear is processed, especially abnormal fear processing. So it makes sense to look at the structure of the amygdala.”
For the study, researchers enrolled 200 combat veterans who served in Iraq and Afghanistan after Sept. 11, 2001. Half of the participants had been diagnosed with PTSD, while the other half had not developed PTSD, even though they had been exposed to trauma.
When amygdala and hippocampus volumes were computed from MRI scans of all the participants, 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 extent of depression, substance abuse, trauma load or PTSD severity did not explain the differences in brain volumes, the authors noted.
Morey said the study raises the question of whether some people may have a greater propensity for developing PTSD because of their 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.”
1. Morey RA, Gold AL, Labar KS, et al. Amygdala Volume Changes in Posttraumatic Stress Disorder in a Large Case-Controlled Veterans Group. Arch Gen Psychiatry. 2012 Nov 1;69(11):1169-1178. PubMed PMID: 23128809.