Threshold Effect of Anxiety in the Comorbidity of Depression and Chronic Pain: A Cross-Sectional Study Based on Pain Sensitivity

Purpose: The considerable co-prevalence of major depressive disorders (MDD), anxiety symptoms, and chronic pain (CP) indicates a complex link with significant treatment ramifications. This study elucidates the role of pain sensitivity as a potential etiological factor in anxiety and depression. Methods: This cross-sectional study recruited 124 participants divided into a health control group (HC, n=48), patients with depression without CP group (MDD, n=38) and comorbidity group of patients with MDD and CP (COM, n=38). Clinical assessments included the Hamilton Depression Rating Scale-24 (HAMD-24), Beck Depression Inventory-II (BDI-II), Hamilton Anxiety Rating Scale-14 (HAMA-14), and Beck Anxiety Inventory (BAI) to evaluate depressive and anxiety symptoms. The 36-Item Short Form Health Survey (SF-36) quantified health-related quality of life, while the Pain Sensitivity Questionnaire (PSQ) and Pain Intensity Numerical Rating Scale (PI-NRS) assessed pain sensitivity and pain intensity, respectively. A piecewise regression model identified clinical thresholds. Results: The COM group showed higher BAI ( U =294.5, p < 0.001) and PI-NRS scores ( U =166.0, p < 0.001) compared to the MDD group. Piecewise regression identified PSQ=4.14 as the critical breakpoint for anxiety’s influence on pain sensitivity. Beyond this threshold, BAI and Bodily Pain slopes reversed significantly ( R 2 =0.2434, p < 0.05; R 2 =0.2085, p < 0.05). The high-PSQ group reported significantly more severe bodily pain (Cohen’s d = − 0.81, p =0.042). Conclusion: Our findings reveal that when pain sensitivity exceeds the threshold (PSQ≥ 4.14), anxiety significantly amplifies pain perception, forming a “pain-anxiety-depression” positive feedback loop. This finding provides an empirical foundation for personalized therapy.