The effects of depression and smoking on pain severity and opioid use in patients with chronic pain.

Depression and smoking are common comorbid conditions among adults with chronic pain. The aim of this study was to determine the independent effects of depression on clinical pain and opioid use among patients with chronic pain according to smoking status. A retrospective design was used to assess baseline levels of depression, clinical pain, opioid dose (calculated as morphine equivalents), and smoking status in a consecutive series of patients admitted to a 3-week outpatient pain treatment program from September 2003 through February 2007. Depression was assessed using the Centers for Epidemiologic Studies-Depression scale, and clinical pain was assessed using the pain severity subscale of the Multidimensional Pain Inventory. The study cohort (n=1241) included 313 current smokers, 294 former smokers, and 634 never smokers. Baseline depression (P=.001) and clinical pain (P=.001) were greater among current smokers compared to former and never smokers, and the daily morphine equivalent dose was greater among smokers compared to never smokers (P=.005). In multivariate linear regression analyses, baseline pain severity was independently associated with greater levels of depression, but not with smoking status. However, status as a current smoker was independently associated with greater opioid use (by 27mg/d), independent of depression scores. The relationship between depression, smoking status, opioid use, and chronic pain is complex, and both depression and smoking status may be potentially important considerations in the treatment of patients with chronic pain who utilize opioids. This study found that pain severity was associated with greater depression but not smoking; however, smoking was associated with greater opioid use, independent of depression.