Title: Elevated perceived threat is associated with reduced hippocampal volume in combat veterans
Legend: (A) In this study of 56 combat veterans, we found that veterans with elevated PTSD symptoms (light green) showed a disconnect between self-reported combat exposure and retrospectively reported perceived threat while deployed, in stark contrast to veterans with low levels of PTSD symptoms (dark green). (B) We collected structural MRI scans and calculated hippocampal volume using FreeSurfer. (C) In more symptomatic veterans, elevated perceived threat while deployed was associated with smaller hippocampal volume. Ongoing research from our group is investigating macrostructural and microstructural properties of the hippocampus in relation to perceived stress, which may shed light on individual differences in risk for stress-related disorders.
Citation: Grupe DW, Hushek BA, Ellis K, Schoen AJ, Wielgosz J, Nitschke JA, & Davidson RJ (2019). Elevated perceived threat is associated with reduced hippocampal volume in combat veterans. Scientific Reports, 17, 14888. doi:10.1038/s41598-019-51533-x.
Abstract: Reduced hippocampal volume is frequently observed in posttraumatic stress disorder (PTSD), but the psychological processes associated with these alterations remain unclear. Given hippocampal involvement in memory and contextual representations of threat, we investigated relationships between retrospectively reported combat exposure, perceived threat, and hippocampal volume in trauma-exposed veterans. T1-weighted anatomical MRI scans were obtained from 56 veterans (4 women, 52 men; 39 with elevated PTSD symptoms, “PTSS” group) and hippocampal volume was estimated using automatic segmentation tools in FreeSurfer. Hippocampal volume was regressed on self-reported perceived threat from the Deployment Risk and Resilience Inventory, and combat exposure from the Combat Exposure Scale. As a secondary analysis, hippocampal volume was regressed on Clinician-Administered PTSD Scale (CAPS) symptoms. In veterans with elevated PTSD symptoms, hippocampal volume was inversely related to perceived threat while deployed while controlling for self-reported combat exposure. Hippocampal volume was also inversely correlated with avoidance/numbing CAPS symptoms. Future research should clarify the temporal milieu of these effects and investigate whether individual differences in hippocampal structure and function contribute to heightened threat appraisal at the time of trauma vs. subsequently elevated appraisals of traumatic events.
About the Lab: Research in Davidson’s laboratory is focused on the neural bases of disordered and healthy emotion and emotional style and methods to promote human flourishing, including meditation and related contemplative practices. His studies have included persons of all ages, from birth though old age, and have also included individuals with disorders of emotion, such as mood and anxiety disorders and autism, as well as expert meditation practitioners with tens of thousands of hours of experience. His research uses a wide range of methods, including different varieties of MRI, positron emission tomography, electroencephalography, and modern genetic and epigenetic methods.