Resting HRV predicts cardiac vagal control during stress, not psychological distress.

Resting heart rate variability (HRV) is considered a marker of individuals' capacity to adapt to environmental demands, although direct empirical evidence remains limited. This study examined whether resting HRV predicts subjective and cardiac reactivity to stress, psychological distress, and emotional regulation (ER) strategies. Eighty-five healthy young adults completed distress (DASS) and cognitive ER (CERQ) scales before undergoing a virtual reality-adapted Trier Social Stress Test. Heart rate (HR), HRV indexed by RMSSD, skin conductance, and subjective stress were recorded across baseline, stress, and recovery. As expected, tasks elicited subjective and autonomic stress responses, and higher resting RMSSD predicted greater RMSSD reactivity and recovery. Contrary to our hypothesis, Bayesian analyses provided evidence for the absence of association between resting RMSSD and HR reactivity and recovery, subjective stress reactivity, psychological distress, and ER strategies. Overall, our findings challenge the view of resting HRV as a reliable index of adaptive capacity to acute stress or of vulnerability to psychological distress. Instead, resting HRV interpretation should be restricted to a predictor of the degree to which the vagal system can modulate cardiac activity. Furthermore, resting HRV's health relevance is likely more tied to long-term cardiovascular vulnerability in the context of repeated or chronic stress.