Military deployment correlates with smaller prefrontal gray matter volume and psychological symptoms in a subclinical population

Abstract

Research investigating the effects of trauma exposure on brain structure and function in adults has mainly focused on post-traumatic stress disorder (PTSD), whereas trauma-exposed individuals without a clinical diagnoses often serve as controls. However, this assumes a dichotomy between clinical and subclinical populations that may not be supported at the neural level. In the current study we investigate whether the effects of repeated or long-term stress exposure on brain structure in a subclinical sample are similar to previous PTSD neuroimaging findings. We assessed 27 combat trauma-exposed individuals by means of whole-brain voxel-based morphometry on 3 T magnetic resonance imaging scans and identified a negative association between duration of military deployment and gray matter volumes in ventromedial prefrontal cortex (vmPFC) and dorsal anterior cingulate cortex (ACC). We also found a negative relationship between deployment-related gray matter volumes and psychological symptoms, but not between military deployment and psychological symptoms. To our knowledge, this is the first whole-brain analysis showing that longer military deployment is associated with smaller regional brain volumes in combat-exposed individuals without PTSD. Notably, the observed gray matter associations resemble those previously identified in PTSD populations, and concern regions involved in emotional regulation and fear extinction. These findings question the current dichotomy between clinical and subclinical populations in PTSD neuroimaging research. Instead, neural correlates of both stress exposure and PTSD symptomatology may be more meaningfully investigated at a continuous level.

Community violence exposure correlates with smaller gray matter volume and lower IQ in urban adolescents

“…Our findings fit with literature showing that community violence exposure is associated with worse cognitive outcomes (Delaney‐Black et al, ; Ratner et al, ; Sharkey, ). Notably, our finding in the ACC overlaps with results from previous studies of soldiers deployed to war (Butler et al, ) and of a PTSD meta‐analysis (Kühn & Gallinat, ). Figure provides the graphical overlay of the current results with results from a study of military deployment (Butler et al, ) and from a PTSD meta‐analysis (Kühn & Gallinat, ).…”

“…Notably, our finding in the ACC overlaps with results from previous studies of soldiers deployed to war (Butler et al, ) and of a PTSD meta‐analysis (Kühn & Gallinat, ). Figure provides the graphical overlay of the current results with results from a study of military deployment (Butler et al, ) and from a PTSD meta‐analysis (Kühn & Gallinat, ).…”

“… Community violence exposure, military deployment, and PTSD. Brain images display the negative correlations between community violence exposure and gray matter volume from the current study in red; results from a previous neuroimaging study showing a negative correlation between military deployment and gray matter volume (Butler et al, ) in blue; and results from a PTSD meta‐analysis (Kühn & Gallinat, ) in magenta. Note the overlapping results in anterior cingulate cortex…”

“…Previous studies have shown that community violence exposure is associated with increased risk for psychiatric illness (McDonald & Richmond, ), but also that parental warmth is protective (Chen, Miller, Kobor & Cole, ). Stress exposure has previously been shown to correlate with smaller PFC gray matter volumes and increased PTSD symptoms in a subclinical population (Butler et al, ). Future work should investigate any link to subtle psychological symptoms associated with gray matter reductions in this age group.…”

Altered White Matter Diffusivity of the Cingulum Angular Bundle in Posttraumatic Stress Disorder

“…The cingulum hugs the corpus callosum and is predominantly comprised of short fibers that connect the cingulate cortex, and nearby regions of the frontal, parietal, occipital, and temporal lobes [22]. Of particular relevance to PTSD, the cingulum connects the cingulate cortex and the hippocampus [15], 2 regions implicated in the pathophysiology of PTSD [23][24][25][26], which, if impaired, may delay or prevent recovery after exposure to trauma due to their respective roles in learning, memory, and fear processing [27]. The UNC connects portions of the temporal lobe with the inferior frontal gyrus [18].…”