Introduction: Accumulating evidence suggests that negative affect is associated with elevated cortisol. Limited research has investigated this association in young, highly functioning, and stress-resilient populations.
Methods: We examined the relation of trait anxiety with total and diurnal salivary cortisol during free-living conditions and during a stressful military exercise in 26 military men ages 19-30 yr (M = 21.6, SD = 2.3). Salivary cortisol was assessed at five time points over 2 consecutive days of free-living measurement, and three time points during a stressful military experience. Trait anxiety was measured with the trait portion of the Spielberger State-Trait Anxiety Inventory 1-3 wk prior to the military exercise.
Results: Total cortisol concentrations were similar between men reporting high or low anxiety during free-living conditions (8.6 +/- 3.2 vs. 7.4 +/- 2.8 nmol x L(-1), respectively, P > 0.05), and military stress (21.3 +/- 7.3 vs. 19.0 +/- 7.0 nmol x L(-1), respectively, P > 0.05). The diurnal cortisol profile differed significantly (P = 0.04) between these men during the free-living condition, but not the stressful military experience (P > 0.05). Specifically, during free living, men with low anxiety exhibited a diurnal cortisol pattern that peaked in the early morning, decreased precipitously during the midmorning, and continued to decrease throughout the day, reaching a nadir in the evening. By contrast, the cortisol pattern of high-anxiety men remained elevated and significantly higher than their low-anxiety counterparts during the midmorning, decreased more slowly throughout the day, and reached its lowest level in the evening. Results were not substantially altered following adjustment for sleep duration or wake time.
Conclusion: These findings suggest that trait anxiety influences the diurnal cortisol pattern in young, apparently healthy men during free-living conditions, but does not predict the cortisol response to uncontrollable military stress.