Associations Between Positive Affect and Heart Rate Variability: A Systematic Review.

PURPOSE OF REVIEW: The relationship between positive affect (PA) and heart rate variability (HRV) has attracted considerable interest due to its potential implications for emotion regulation and cardiovascular health. This systematic review synthesizes current literature on the association between PA and HRV, considering resting-state, stress-reactivity and recovery contexts, as well as variations in PA conceptualization. RECENT FINDINGS: A total of 36 studies (N = 5501) were included, spanning experimental, ambulatory, cross-sectional, and mixed designs. Elevated PA was most often associated with higher vagally mediated HRV, measured as RMSSD or high-frequency (HF) power, but results varied by context. Resting-state and trait-like PA measures showed the most consistent positive associations. In stress-induction paradigms, effects depended on the stress phase and arousal level of PA, with RMSSD emerging as a more consistent index than other HRV metrics. In real-life settings, aggregated activated PA was linked to higher RMSSD, while momentary activated PA was linked to lower RMSSD, suggesting short-term allostatic adjustments. Findings for other HRV metrics, such as LF/HF ratio, LF-HRV, and SDNN, were mixed. Overall, this review highlights the complex interplay between PA and cardiac autonomic regulation and provides directions for future research, which should aim for greater methodological consistency and clarify the temporal dynamics of the PA-HRV relationship.