Examining the Link between Reciprocal Pain and Depression

Findings from a new study published in The Journal of Pain suggest that changes in pain severity can predict subsequent depression severity, and that a worsening change in depression is an equally strong predictor of subsequent pain severity.

Researchers at Indiana University studied 250 patients with musculoskeletal pain and comorbid depression and 250 patients with pain and no depressive symptoms, all of whom were treated in primary care practices and enrolled in the Stepped Care for Affective Disorders and Musculoskeletal Pain (SCAMP) study. Outcomes were assessed at 3, 6, and 12 months.

The authors sought to determine whether pain and depression exhibit predictable influences on each other over 12 months. Previous studies have documented the linkage of pain and depression, but the cause-and-effect relationship of the 2 conditions lacked clarification. Although chronic pain is well known risk factor for depression, it is not known if depression can be considered a risk factor for pain.

For the study, pain severity was measured by the Graded Chronic Pain Scale and depression levels were assessed with Hopkins Symptom Checklist, a 20-item questionnaire widely used in primary care. The mean age of the study sample was 59 years and 52% of the subjects were women.

The results indicated that both pain and depression appeared to influence each other. Change in pain was found to be a strong predictor of subsequent depression severity, and a change in depression severity was an equally strong predictor of pain severity. Analyses also showed that the effects of pain on depression were mediated by its effects on fatigue and disability.

The authors noted that a number of explanations for the findings are possible. From a physiological perspective, both nociceptive and affective neurological pathways coincide anatomically. The neurotransmitters noreprinephrine and serotonin, which are integral in mood disorders, also are involved in pain mechanisms. In addition, mood disorders may heighten attention to painful stimuli. Poor pain coping, low self efficacy, and other cognitive behavioral factors could have some influence as well.

The authors concluded that the frequent co-occurrence of pain and depression and their reciprocal influence on each other should direct clinicians to assess these conditions jointly rather than separately. Therefore, detection of one should trigger a search for the other. This approach is warranted because the presence of both pain and depression is associated with suboptimal treatment outcomes, greater disability and increased health care use and cost.