Cigarette smoking and pain: depressive symptoms mediate smoking-related pain symptoms.

Numerous studies have shown an association between smoking and pain, with smokers reporting more pain and worse functioning. However, little is known about factors that impact this complex relationship. This study investigated the association between smoking, pain, and depressive symptoms. Participants were new patients seen at a multidisciplinary pain clinic. All patients were mailed an intake packet of validated questionnaires as part of an ongoing research and clinical care initiative. Of the 497 patients evaluated, 426 had valid smoking data. Among these patients, 32.6% (n = 139) reported being current smokers, 31.7% (n = 135) were classified as former smokers, and 35.7% (n = 152) were never smokers. A multivariate analysis of covariance (smoking status, age, gender, education) revealed a main effect for pain severity (F = 7.36, P<0.001), pain interference (F = 4.03, P = 0.001), and depressive symptoms (F = 7.87, P<0.001). Current smokers demonstrated higher pain severity, pain interference, and depressive symptoms compared with former smokers and never smokers (P<0.01 for all analyses), while there were no differences between the former-smoker and never-smoker groups. However, the effect of smoking on pain severity (P = 0.06) and pain interference (P = 0.22) was no longer significant after controlling for depressive symptoms in a mediation model. Additionally, among former smokers, longer quit duration was associated with less pain severity. In conclusion, smoking rates were high and smoking was associated with a worse chronic pain phenotype. Importantly, depressive symptoms emerged as a critical mediating factor in helping to explain the relationship between smoking and pain.