An association between depression and inflammation has been suggested. In patients with rheumatoid arthritis (RA), pain is a major symptom associated with depression and inflammation. We examined the independent associations between depression, the inflammation marker C-reactive protein (CRP) level, and pain in patients with RA.
In total, 218 RA outpatients completed self-administered questionnaires, using the Beck Depression Inventory II to measure depressive symptoms and a visual analog scale to quantify their perceived pain. Functional disability and CRP level were also measured.
Depression scores were mildly and positively correlated with the CRP level (r = 0.46, P < 0.001). Both the depression score (standardized beta = 0.35, P < 0.001) and the CRP level (standardized beta = 0.35, P < 0.001) were significantly associated with pain, even after adjustment for clinical covariates in regression analysis. In logistic analysis, the combined effects on the risk of severe pain (pain score in the upper tertile) increased with depression scores and CRP levels linearly.
Depression severity and inflammation were associated with each other and appeared to have independent effects on perceived pain. Therefore, a clinical approach that takes into account both the body and the mind could have benefits and could enable optimal pain control.