Heart rate variability moderates the between- and within-person associations between daily stress and negative affect

Stress exposure increases risk for depressive symptoms. However, there are substantial individual differences in affective responses to stress. High-frequency heart rate variability (HF-HRV), a marker of vagally-mediated parasympathetic activity, has been conceptualized as a psychophysiological index of emotion regulation that may moderate individuals? responses to stress. Using a daily diary design, we tested whether individual differences in resting HF-HRV moderated the association between daily child-related stress and negative affect among a sample of 84 heterosexual couples with preschool-aged children. After controlling for participants? age, gender, socioeconomic status, employment status, and ethnicity, hierarchical linear modeling revealed that resting HFHRV moderated both the between-person and within-person associations between self-reported child-related stress and daily negative affect. Between-person analyses indicated that the strength of the positive association between mean daily child stress and negative affect across the daily diary period increased with decreasing resting HF-HRV. Similarly, within-person analyses indicated that on days when participants reported more childrelated stress than usual, the magnitude of the increase in negative affect on that day was inversely related to resting HF-HRV. Taken together, these findings suggest that lower resting HF-HRV may index vulnerability to stress-related disturbances in negative affect. This increased negative affective response to daily stress may be one pathway through which individuals with lower resting HF-HRV are at increased risk for depressive symptoms over time.