(HealthDay News) – Compared with trauma-exposed control patients, veterans with posttraumatic stress disorder (PTSD) have a significantly smaller amygdala volume that is not affected by the trauma load, chronicity of PTSD, or depressive symptom severity.

To examine the effect of PTSD on volumetric changes in the amygdala and hippocampus, Rajendra A. Morey, MD, of the Duke-University of North Carolina Brain Imaging and Analysis Center in Durham, and colleagues conducted a case-control study involving patients recruited from a registry of military service members and veterans. Cases included 99 veterans with current PTSD, while the control group comprised 101 trauma-exposed individuals without PTSD.

The researchers found that, compared with the non-PTSD group, significantly smaller volume was demonstrated in the PTSD group for the left amygdala, right amygdala, and left hippocampus, but not for the right hippocampus. There was no correlation for amygdala volumes with PTSD chronicity, trauma load, or depressive symptom severity.

“These results provide robust evidence of an association between a smaller amygdala volume and PTSD,” the authors write. “When considered in the context of previous translational research linking smaller amygdala volume with stronger fear conditioning and stress response, our results are consistent with the theory that a smaller amygdala represents a vulnerability to developing PTSD rather than an outcome of the disorder.”

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