Amygdala Volume in Combat-Exposed Veterans With and Without Posttraumatic Stress Disorder

Abstract

Data from animal models demonstrate a link between stress exposure and hypertrophic changes in the amygdala; however, studies of adults with posttraumatic stress disorder (PTSD) have failed to find analogous structural alterations. To compare amygdala volumes between a sample of combat veterans with and without PTSD (analysis 1) and examine whether our observation of larger amygdala volume in individuals with PTSD could be accounted for by the presence of trauma exposure in childhood and the severity of combat exposure in adulthood (analysis 2). Cross-sectional magnetic resonance imaging. Veterans Affairs Palo Alto Health Care System Inpatient Trauma Recovery Program and Veterans Affairs New England Health Care System Outpatient PTSD program. Ninety-nine combat-exposed veterans from the Vietnam Conflict or the Persian Gulf War who had been exposed to substantial military operational stress. Amygdala volume adjusted for total cerebral volume, Life Events Checklist, and the Combat Exposure Scale. Analysis 1 indicated that combat-exposed individuals with PTSD exhibited larger total amygdala volume compared with their non-PTSD counterparts (99 individuals, P = .047). Analysis 2 indicated that greater severity of combat exposure (87 individuals, P = .02), as well as the interaction between the presence of early life trauma and the severity of combat exposure (87 individuals, P = .008), were significantly associated with smaller total amygdala volume. The PTSD diagnosis continued to explain larger amygdala volume (87 individuals, P = .006). Posttraumatic stress disorder is associated with enlarged amygdala volume, above the variance accounted for by a history of early life trauma and severity of adult trauma exposure. The discrepancy between our and prior findings may be explained by variability in these trauma indices in previous investigations. These findings support additional study of amygdala structure in human stress disorders and further delineation of the role of early and adult trauma on associated neurologic changes.