The Stress of Combat

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Science Translational Medicine  26 Sep 2012:
Vol. 4, Issue 153, pp. 153ec173
DOI: 10.1126/scitranslmed.3004988

Stress can do more than make you lose sleep or eat too much junk food: It can also affect cognitive function. In humans, acute stress can impair working memory and attention, but the long-term consequences of severe stress on the brain are unknown. Looking at a select, high-stress cohort, van Wingen et al. evaluated the neural impact of combat stress by examining soldiers before and after deployment to Afghanistan.

The authors used a prospective longitudinal neuroimaging study design to examine the brains of 33 healthy soldiers before and 1.5 months and 1.5 years after their exposure to severe stress during their first military deployment to a combat zone. An additional 26 healthy soldiers who were never deployed were studied at similar time intervals to control for repeated testing and other nonspecific effects. van Wingen and colleagues found that combat stress reduced midbrain activity and integrity and resulted in disrupted sustained attention. Long-term follow-up showed that these functional and structural changes observed initially had normalized within 1.5 years. However, combat stress induced a persistent reduction in functional connectivity between the midbrain and prefrontal cortex that lasted 1.5 years.

These results suggest that in healthy humans, the brain can largely recover from the adverse effects of stress. However, the results also reveal long-term changes within the network of brain regions that connect the midbrain and the prefrontal cortex. The disruption of this network may increase the vulnerability of the brain to subsequent stressors and lead to more persistent cognitive deficits. Although this study focused on a small cohort of soldiers who sustained no physical injury during their combat exposure (and may therefore not represent the general military population), the authors have highlighted the long-term impact of combat stress on the brain’s most vulnerable regions that support critical cognitive functions. Further study is needed to determine whether strategies such as lengthening time home between deployments would facilitate the brain’s recovery from combat stress exposure.

G. A. van Wingen et al., Persistent and reversible consequences of combat stress on the mesofrontal circuit and cognition. Proc. Natl. Acad. Sci. U.S.A. 109, 15508–15513 (2012). [Abstract]

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