Circulating Biomarkers of Military-Specific Performance Resilience: A Systematic Review

To systematically examine the available literature on circulating biomarkers of performance resilience in a military environment, with the goal of identifying the most promising circulating biomarkers.

The construct 'resilience' is hypothesized to play an important role in increasing Special Operations Forces' and other military personnel's capacity for withstanding exposure to various military-specific stressors. However, objectively measuring resilience is challenging. Some of the most important and well-studied circulating biomarkers that affect military-specific resilience are cortisol, dehydroepiandrosterone (sulfate) [DHEA(S)], noradrenaline, serotonin, neuropeptide-Y (NPY) and brain-derived neurotrophic factor. Despite growing evidence, the available knowledge is yet to be summarized and reviewed while considering the intensity and duration of military-specific stressors, military experience, and methodological differences between studies. Cortisol, Insulin-like growth factor-1 (IGF-1), NPY and DHEA(S) provide a physiological window into military-specific resilience. In general, individuals who exhibit a pronounced but controlled biomarker response to an acute stressor, combined with a quick recovery to baseline, demonstrate physiological flexibility that is associated with greater military-specific resilience. Future research will need to determine relative thresholds for the acute stressor-related change in circulating biomarkers and relative timing to stressor, to correctly interpret 'a pronounced but controlled biomarker response' and 'quick recovery to baseline'.