Adverse childhood experiences (ACE) reportedly promote medical and psychiatric morbidity and maladaptive reactivity to stress throughout life. To explore the impact of ACE on army cadets undergoing stressful training conditions, a cohort of healthy cadets in an elite Israel Defense Forces unit was screened using the Childhood Trauma Questionnaire (CTQ) for exposure to childhood adversity. Two extreme case-control subgroups with high scores (childhood adversity [CA] subgroup, n = 43) or null scores (nonchildhood adversity [NCA] subgroup, n = 43), were further assessed before, and in the middle of a high intensity combat-simulation training week. Compared with the NCA subgroup, at baseline, the CA group exhibited higher state anxiety (p < .001), trait anxiety (p < .001) and depression (p < .001), and poorer executive functioning on the Behavior Regulation Index (BRI, p = .001) and Metacognition Index (MI, p < .001). At the height of the combat-simulating training week, however, the scores of the CA subgroup were not significantly higher than their baseline scores for depression, trait anxiety, BRI, or MI. By contrast, relative to their baseline scores, the NCA subgroup's scores during the combat-simulating week were significantly increased for state anxiety (p < .001) and BRI (p = .004). Exposure to CA results in significant long-term alterations in anxiety, depressive symptoms, and executive functioning, as well as stress reactivity. Living with constantly increased vigilance may either be protective or merely saturate symptomatic increments when facing external stress. [ABSTRACT FROM AUTHOR]