Objective sleep efficiency moderates the association between depressive symptoms and experimental heat pain sensitivity in pain-free adults: A cross-sectional study.

BACKGROUND: Depression is highly comorbid with pain, yet experimental evidence reports inconsistent (either increased or decreased) pain sensitivity in depression. Recent evidence also highlighted the role of sleep in altered pain perception. Sleep may moderate the depression-pain relationship, although this remains unexplored in pain-free populations. This study examined whether depressive symptoms are associated with pain sensitivity and whether sleep moderates this effect. We hypothesized that higher depressive symptoms would predict lower pain sensitivity (higher pain thresholds) and that higher sleep efficiency would attenuate this relationship.

METHODS: Participants (N = 49; 34 females) aged 18 to 50 (M = 25.59, SD = 6.17) completed the Beck Depression Inventory and pain measures (heat, cold, and pressure pain thresholds) at two lab sessions one week apart. Between-session sleep efficiency was measured both objectively (actigraphy) and subjectively (Pittsburgh Sleep Quality Index).

RESULTS: Multiple regression analyses showed that depressive symptoms were not associated with pain thresholds. However, actigraphy-derived sleep efficiency moderated the association such that higher depressive symptoms corresponded to higher heat pain thresholds at high sleep efficiency (>89%). No interaction was found for other pain thresholds or subjective sleep, and findings require replication.

CONCLUSION: Although depression may not directly predict altered pain processing, this is the first experimental study to show a moderating role of objective sleep efficiency in the depression-pain link, potentially explaining mixed findings in past research that did not account for sleep. Our results extend current depression-pain models, highlighting the importance of objective sleep in understanding vulnerability to pain in depression.