One of the most common mental illnesses is major depressive disorder, which affects an estimated 2 to 6 percent of the general population. Recent studies have found an association between multiple long-term medical conditions and depression. For instance, patients with chronic pain have been shown to have an increased rate of psychiatric diagnoses compared with the general population. In addition, nondepressed patients with a long-term medical condition were twice as likely to develop major depression within one year compared with persons who did not have long-term medical conditions. Few studies have been conducted to determine whether patients with chronic painful physical conditions have an increased likelihood of developing major depressive disorders. Ohayon and Schatzberg examined the relationship between chronic, painful conditions and depression in a large community sample.

The study was a cross-sectional telephone survey of a random sample of adults from five different countries. The telephone survey was based on the Sleep-EVAL System, a computer-based questionnaire that covers sociodemographics, sleep/wake schedule, physical health, and sleep and mental disease symptoms. Information about pain was gathered through questions concerning the treatment of medical conditions at the time of the study, current medication use, and any disease the participants were treated or hospitalized for in the past 12 months. Chronic, painful physical conditions were divided into five categories: joint/articular conditions, limb pain, backache, headache, and gastrointestinal diseases.

A total of 18,980 persons completed the survey, 17 percent of whom reported having at least one of the chronic, painful physical conditions. Approximately 17 percent of respondents had at least one depressive symptom, such as sadness, depression, hopelessness, loss of interest, or lack of pleasure. Of those with depressive symptoms, 28 percent had at least one chronic, painful physical condition. Major depressive disorder affected 4 percent of respondents, and of those, 43 percent reported at least one chronic, painful condition. Persons with major depressive disorder were four times more likely to report a chronic, painful physical condition than those without major depressive disorder. Chronic, painful physical conditions were strongly associated with major depressive disorders.

The authors conclude that the presence of chronic, painful physical conditions increases the duration of depressive mood. They add that patients with chronic pain should be systematically evaluated for depression.

editor's note: The interaction between physical and psychosocial forces is more pronounced in patients with pain syndrome. Perceptions of pain and the way patients respond to it vary. In some cases, as noted by Ohayon and Schatzberg, chronic pain can increase the duration of a depressive mood. In addition, physicians who treat patients with chronic pain should evaluate these patients for depression on a continual basis. If we identify and treat depression in patients with chronic pain, they may require less narcotic medication and have a better quality of life. By paying attention to the interaction of the physical with the mental, we can improve outcomes in these challenging patients.—K.E.M.