Comorbid Depression, Chronic Pain, and Disability in Primary Care

Objectives: The objectives of this study were to provide estimates of the prevalence and strength of association between major depression and chronic pain in a primary care population and to examine the clinical burden associated with the two conditions, singly and together. Methods: A random sample of Kaiser Permanente patients who visited a primary care clinic was mailed a questionnaire assessing major depressive disorder (MDD), chronic pain, pain-related disability, somatic symptom severity, panic disorder, other anxiety, probable alcohol abuse, and health-related quality of life (HRQL). Instruments included the Patient Health Questionnaire, SF-8, and Graded Chronic Pain Questionnaire. A total of 5808 patients responded (54% of those eligible to participate). Results: Among those with MDD, a significantly higher proportion reported chronic (i.e., nondisabling or disabling) pain than those without MDD (66% versus 43%, respectively). Disabling chronic pain was present in 41% of those with MDD versus 10% of those without MDD. Respondents with comorbid depression and disabling chronic pain had significantly poorer HRQL, greater somatic symptom severity, and higher prevalence of panic disorder than other respondents. The prevalence of probable alcohol abuse/dependence was significantly higher among persons with MDD compared with individuals without MDD regardless of pain or disability level. Compared with participants without MDD, the prevalence of other anxiety among those with MDD was more than sixfold greater regardless of pain or disability level. Conclusions: Chronic pain is common among those with MDD. Comorbid MDD and disabling chronic pain are associated with greater clinical burden than MDD alone. MDD = major depressive disorder; HRQL = health-related quality of life; HMO = health maintenance organization; PHQ = Patient Health Questionnaire; GCPS = Graded Chronic Pain Scale; CP = chronic pain; DCP = disabling chronic pain; GAD = generalized anxiety disorder; SCID = Structured Clinical Interview for DSM-III-R; PRIME-MD = Primary Care Evaluation of Mental Disorders; CI = confidence interval; DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition; DSM-III-R = Diagnostic and Statistical Manual of Mental Disorders, Third Edition Revised.