State rumination links major life stressors to acute stressor cortisol response in healthy adults.

Experiencing major life stressors is associated with negative health outcomes, yet the mechanisms are not fully understood. Major stressors are threatening, discrete events that can have lingering consequences on emotional and cognitive processes. This can lead to maladaptive coping strategies, such as rumination, that compromise the ability to handle subsequent stressors and disrupt the hypothalamic-pituitary-adrenal (HPA) axis response. Based on the Perseverative Cognition Hypothesis, it was hypothesized that greater exposure to major stressors would be associated with greater rumination during a laboratory stressor, which, in turn, would predict higher cortisol reactivity and peak and delayed recovery. Participants were 211 healthy adults (M = 30.2, SD = 10.9, range = 18 - 55) who underwent the Trier Social Stress Test and self-reported rates of major stressors in the past 12 months and stress-related state rumination. Two-piece growth curve modeling with landmark registration was used to calculate peak salivary cortisol levels along with cortisol reactivity and recovery slopes to capture individual differences in the trajectory of cortisol response. Results showed that state rumination significantly mediated the link between more major stressors and elevated peak cortisol levels as well as steeper reactivity and recovery slopes. Interpersonal stressors and non-interpersonal stressors showed similar associations to cortisol response via state rumination. This study enhances our understanding of how stress contributes to HPA axis dysregulation by connecting major stressors with acute stressors, pointing at stress-induced rumination as a plausible mechanism.