Heart Rate Variability Mediates the Association Between Fear of Pain and Pain Perception: An Exploratory Study in Healthy Controls

<b>Background/Objectives</b>: Fear of pain (FoP) is a critical psychological factor influencing the experience of pain, yet the mechanisms behind this relationship remain unclear. HRV, indexed here by resting RMSSD, reflects individual differences in cardiac vagal tone and has been linked to pain perception and pain-related psychological processes. In this exploratory, cross-sectional study, we examined whether HRV mediates the relationship between FoP and the subjective perception of pain intensity. <b>Methods</b>: Twenty-two healthy participants completed several self-reported measures, including the Fear of Pain Questionnaire (FPQ-SF), and underwent an experimental cold pain induction, as well as a continuous recording of HR at rest. Mediation analysis was performed to assess the indirect effect of HRV, calculated via the Root Mean Square Successive Difference (RMSSD), on cold pain perception. <b>Results</b>: In correlational analyses, the Fear of Severe Pain (FoSP) subscale was associated with lower resting logRMSSD and higher cold pain ratings. In mediation models, the pattern of results was consistent with an indirect association between FoSP and cold pain ratings via logRMSSD (bootstrap 90% CI), while the direct path from FoSP to pain was not significant. <b>Conclusions</b>: These preliminary findings are hypothesis-generating and suggest that individual differences in resting HRV may be one physiological correlate of the fear-pain relationship in healthy controls, rather than an index of autonomic responses during pain itself. Larger longitudinal and experimental studies are needed to test temporal ordering, specificity across FoP components, and whether autonomic measures during pain better explain fear-pain coupling.