Effects of Exposure to Life Stressors, Perceived Stress, and Psychopathological Symptoms on Cortisol Awakening Response: Individual Differences in Resilience.

Cortisol awakening response (CAR) has been proposed as a viable biomarker for assessing the function of the hypothalamic-pituitary-adrenal axis. However, there are inconsistencies within the literature on the relationship between CAR and psychopathology. This study examined the unique effects of psychopathological symptoms on hypothalamic-pituitary-adrenal axis functioning (indexed through CAR) while considering the effects of exposure to major life stressors and self-reported perceived stress. The sample consisted of 71 participants, aged 25-37 years old. The Life Stress Index, Perceived Stress Scale, and Symptom Checklist-90 were administered. Salivary cortisol samples were collected across five time points (1 pre-bedtime and 4 upon awakening). A generalised additive model revealed a non-linear effect of time on cortisol concentration upon awakening, characterising CAR's prototypical inverted U-shaped pattern. The analysis also revealed a unique linear relationship between major life stressors and cortisol concentration. That is, greater exposure to major life stressors over the past 5 years was associated with elevated CAR. By contrast, there was also a unique linear relationship between psychopathological symptoms and cortisol concentration in the opposite direction. Contrary to expectations, our findings suggest that exposure to major life stressors, but not perceived stress, may increase cortisol awakening response, which may have implications for negative mental health outcomes (i.e., potential protective factor). These results highlight the importance of considering the complex interplay between stressors and psychopathological symptoms in understanding resilience.