Depression, pain, and functional impairment across fibromyalgia, rheumatoid arthritis, and systemic lupus erythematosus: A cross-condition analysis and mediation model.

BACKGROUND

Depression, pain amplification, and functional impairment are central features of fibromyalgia (FM) and contribute to disability across chronic rheumatic diseases. However, cross-condition differences and shared mechanisms remain unclear.

OBJECTIVES

To evaluate depression, pain, central sensitization, and functional impairment across FM, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and healthy controls (HC), and to examine whether pain mediates the association between depressive symptoms and functional impairment.

METHODS

We analyzed 876 adults (FM n = 591; RA n = 130; SLE n = 94; HC n = 61). Measures included the Beck Depression Inventory (BDI), McGill Pain Questionnaire (MPQ), Revised Fibromyalgia Impact Questionnaire (FIQR), Symptom Impact Questionnaire (SIQR), Central Sensitization Inventory (CSI), and SF-36 subdomains. Group differences were assessed using ANOVA/ANCOVA adjusting for age, sex, and BMI. Mediation (BDI → MPQ → FIQR) was evaluated using bootstrapped structural equation modeling (2000 draws), adjusting for covariates.

RESULTS

FM exhibited the highest levels of depression, pain, central sensitization, and functional impairment (all p < 0.001), with RA and SLE intermediate and HC lowest. Depressive symptoms were associated with pain severity (β = 3.17, p < 0.001), and pain with functional impairment (β = 1.05, p < 0.001). The indirect effect was significant (β_indirect = 3.34; 95% CI [2.65, 4.02]), indicating partial mediation.

CONCLUSIONS

Depressive symptoms, pain severity, and functional impairment are strongly associated across rheumatic conditions, with partial mediation through pain. Elevated central sensitization in RA and SLE suggests shared amplification pathways, supporting integrated treatment approaches targeting mood, pain, and function.