Amygdala Volume Changes in Posttraumatic Stress Disorder in a Large Case-Controlled Veterans Group

Abstract

The amygdala is perhaps the most strongly implicated brain structure in the pathophysiology of posttraumatic stress disorder (PTSD). Prevalent models of anxiety have focused on an amygdalocentric neurocircuitry¹ that is critical in the fear response, conditioning, and generalization^2-4 and facilitates the response to stressful experiences.⁵ Functional magnetic resonance imaging (MRI) studies^6-9 have shown that individuals with PTSD have an exaggerated amygdala response to emotional stimuli when compared with control subjects. Animal studies have demonstrated changes in amygdala morphology with chronic stress,¹⁰ evident primarily in the growth of dendritic spines. Experimental studies of amygdala volume in mice and humans have shown an association among smaller amygdala volumes, increased levels of fear conditioning, and an exaggerated glucocorticoid response to stress.^11-13 However, efforts to find evidence of an association between amygdala volume and PTSD in humans have produced equivocal results.^14,15 Our goal was to reinvestigate amygdala volume changes in PTSD by addressing some of the potential methodological issues contributing to inconclusive findings.