The brain at war: effects of stress on brain structure in soldiers deployed to a war zone

Abstract

In search of the neural basis of severe trauma exposure and post-traumatic stress disorder (PTSD), a multitude of cross-sectional studies have been conducted, most of them pointing at structural deficits in the hippocampus and medial prefrontal cortex including the anterior cingulate cortex (ACC) and ventromedial prefrontal cortex (vmPFC). Since cross-sectional studies are silent to causality, the core question remains: which brain structural alterations constitute a risk factor for disease and therewith precede the stressor, and which brain regions may undergo alterations as a consequence of exposure to the stressor. We assessed 121 soldiers before and after deployment to regions of war and 40 soldiers as controls, who were not deployed. Analysis using voxel-based morphometry revealed volumetric reductions in the ACC, vmPFC (region of interest analysis, effect does not survive conservative multiple test correction) and in bilateral thalamus (whole-brain analysis) in the deployment group. Remarkably, the ACC and vmPFC volume decrease was not limited to the period of deployment, but continued over the following 6 months after deployment. Volumetric reductions did not correlate with increases in PTSD symptoms. The volume decreases in medial prefrontal cortex and thalamus seem to be driven by trauma exposure rather than a vulnerability factor for PTSD. However, data indicate that the volume decrease in medial prefrontal cortex surpasses the time period of deployment. This may hint at an initiated pathobiological process below a symptom threshold, potentially paving the way to future mental health problems.

Large-scale societal dynamics are reflected in human mood and brain

“…In a broader perspective, previous research has suggested that the events that happen in the society have a clear impact on the brain. For example, previous studies have identified reductions in the prefrontal cortex following earthquakes 11 and warzone experiences 12 . One study has demonstrated how a single extreme aversive global event may impact fear circuits by linking individuals’ geographical proximity to the site of 9/11 terrorist attacks to the reactivation of the amygdala during memory recollection 13 .…”

Structural brain features signaling trauma, PTSD, or resilience? A systematic exploration

“…Furthermore, it is not clear whether the resilience cluster represents general resilience against stressors (a genetic predisposition), so that the same characteristics may protect individuals from other mental health disorders, such as depressive ones (Bromis et al, 2018), or specific protective qualities against traumatic events. Third, although some studies sought to demonstrate causality (Gilbertson et al, 2002;Kasai et al, 2008;Kremen et al, 2012;Kühn et al, 2021), in the present study it is not possible to determine whether the volumetric differences between the clusters preceded the trauma exposure or were acquired as the result of confronting trauma without developing PTSD. The differences between the clusters in race may reflect the way in which social determinants of mental health may shape health inequalities, for example by causing added risk, then leading to lower resilience (Alegría et al, 2018;Bailey, 2015).…”

Gray Matter Volume of Thalamic Nuclei in Traumatized North Korean Refugees

“…Reduced thalamic volume is reportedly associated with the frequency and duration of re-experience of trauma in traumatized humans ( 39 ). Thalamic volume is also reportedly associated with childhood maltreatment among high school students and exposure to trauma among deployed soldiers ( 15 , 40 ). While reduced thalamic volume is reportedly associated with psychological disturbances after trauma, increased thalamic GM volume might reflect neurobiological resilience to trauma.…”