Objective Negative Evaluation Level, Perceived Stress, and Autonomic Reactivity in a Lab-based Stress Induction: A Test of Moderated Mediation in a Three-Variable System

Objective stress exposure (the impartial level of threat) and perceptions of stress (subjective level of threat a person endorses feeling) have both been closely linked to physiological and emotional stress-responding. The autonomic nervous system (ANS) is stress-responsive, integral to physical health, and implicated in mental health outcomes. We hypothesize that perceived stress is likely to be one mechanism (i.e., mediator) via which objective stress exerts an effect on ANS reactivity, but also the relationship between perceived stress and ANS reactivity may intensify as objective stress increases (i.e., moderation)—that is, potential moderated mediation in a 3-variable system (Goldstein et al., 2021). 128 emerging adults were randomized to three versions of the Trier Social Stress Test (TSST) that varied in objective level of negative evaluation: none (a control), intermediate/ambiguous, and explicit. The Primary Appraisal Secondary Appraisal Scale (PASA) measured perceived stress following TSST preparation. Salivary alpha amylase, systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR) were measured four times. We tested the hypotheses of moderated mediation in a three-variable system with separate models for each outcome in Mplus Version 8. Objective stress (TSST Condition) directly predicted SBP (p=.018) but did not predict other ANS outcomes. Moreover, no significant moderated mediation (indirect effects varying on objective negative evaluation level) was observed. Stress condition was weakly related to both ANS reactivity and to our measure of perceived stress, Primary Appraisal from the PASA, and future work could investigate more sensitive mediators and outcomes.