Genetic markers of stress, resilience and success at an elite military selection course

Abstract

To qualify for training as elite U.S. Army Special Forces (SF) soldiers, candidates must complete the extremely stressful 19–20 day Special Forces Assessment and Selection (SFAS) course. At SFAS, soldiers must excel at stressful cognitive and physical challenges including team problem solving, foreign language testing, land navigation, timed loaded road marches, timed runs, and challenging obstacle courses. Approximately 70 % of soldiers who attempt SFAS fail. To investigate genetic factors associated with cognitive and physiological biomarkers of resilience and success at SFAS, single nucleotide polymorphisms (SNPs; n = 116) from 47 genes associated with psychological function, resilience, circadian rhythms/sleep, and biomarkers of stress (cortisol and C-reactive protein [CRP]) were examined. Study volunteers were 800 males enrolled in SFAS (age=25±4y; height=178.1 ± 7.5 cm; body mass=82.5 ± 9.2 kg; mean±SD). Genes associated with resilience and their functions included: tryptophan hydroxylase 2 (TPH2; serotonin synthesis); catechol-O-methyltransferase (COMT; catecholamine catabolism); corticotropin-releasing hormone receptor1 gene (CRHR1; resilience to stress); Period3 (PER3; circadian rhythmicity); FK506 binding protein5 (FKBP5; steroid receptor regulation). In summary, several genetic variants are associated with cognitive function and resilience in healthy volunteers exposed to 19–20 days of severe physical and cognitive stress designed to select the best candidates for several years of training. This study extends findings of research on resilience genetics to a novel population and situation, mentally and physically stressed soldiers competing for the opportunity to be trained for an elite unit. The findings indicate that several genes known to be associated with resilience exert their effects on the resilience phenotype under very difficult circumstances than usually studied.