Symptoms of Depression Are Associated With Opioid Use Regardless of Pain Severity and Physical Functioning Among Treatment-Seeking Patients With Chronic Pain

Depression may be a critical factor in the initiation and maintenance of opioids. This study investigated the association among opioid use, pain, and depression in patients evaluated at a university-based outpatient pain clinic. Of the 2,104 new patients included, 55.89% reported current opioid use and showed a worse phenotypic profile (eg, higher pain severity, worse physical functioning) compared with nonopioid users. In addition, more opioid users reported symptoms suggestive of depression than those not taking opioids (43.6% vs 26.8%, P < .001). In a multivariate logistic regression model, increased pain severity was associated with increased probability of taking opioids; however, this was moderated by depression (estimate = -.212, P < .001). For nondepressed patients, the predicted probabilities of opioid use increased as pain severity increased. In contrast, among patients with symptoms of depression, the probability of taking opioids did not change based on pain severity. Similarly, although increased physical function was associated with increased probability of opioid use, this was moderated by depression (estimate = .033, P = .034). Patients with symptoms of depression were more likely to be taking opioids at higher levels of functioning (Ps < .03). Perspective: This study investigated the association among opioid use, pain, and depression at a university-based outpatient pain clinic. Depression emerged as a moderator of the relationship among opioid use, pain severity, and physical functioning. These findings lend support to the hypothesis that patients may be self-medicating affective pain with opioids. (C) 2015 by the American Pain Society