Military unit cohesion has been shown to correlate with physical and psychological outcomes. However, little is known about the development of cohesion in the early days of military service during Basic Combat Training (BCT) and how it relates to positive support and the negative stressors of training. The current study assessed the development of unit cohesion across the 10-week BCT period (N = 1,939), and the relation of cohesion to stress, resilience, mental health measures, and BCT outcomes (graduation, passing the Army Physical Fitness Test, and final Basic Rifle Marksmanship scores). The sample was primarily male (62%), under age 25 (88%), and unmarried (88%). All putative mediators showed significant change over time. Unit cohesion increased over time (slope 0.22; p < .001), and these increases were associated with decreases in psychological distress (p < .001), sleep problems (p < .001), and tolerance of BCT stressors (p < .001), as well as increases in resilience (p < .001), confidence managing stress reactions (p < .001), and positive states of mind (p < .001). Unit cohesion was indirectly associated with successful graduation and passing the Army Physical Fitness Test through cohesion-related improvement in psychological distress, resilience, and confidence managing reactions to stress. Sleep problems also mediated BCT graduation. Cohesion effects on the Basic Rifle Marksmanship scores were mediated by psychological distress and tolerance of BCT stressors only. These results suggest that unit cohesion may play a key role in the development of psychological health among new soldiers
