Mediators of change in depressed mood following pain rehabilitation among participants with mild, moderate, or severe depressive symptoms.

Background: Prior research indicates that depression and chronic pain commonly co-exist and impact each other. Interdisciplinary pain rehabilitation programs (IPRPs) have been shown to lead to statistically and clinically significant improvements for patients who report both depressed mood and chronic pain, however there is a gap in the literature regarding the mechanisms by which these improvements occur.

Methods: This two-site, distinct sample study (Study 1: N = 303, 10-week, individual format, ACT-based program; Study 2: N = 406, 3-week, group format, CBT-based program) evaluated mediators of treatment improvement in depressive symptoms among adult IPRP participants who reported elevated depressive symptoms at program admission and examined treatment mechanisms for depressive symptoms.

Results: Self-reported pain self-efficacy and pain catastrophizing - particularly the helplessness domain - mediated the treatment-related change in depression among IPRP participants with elevated depressive symptoms across the two sites and samples. In one sample, full mediation was achieved while in the other sample, partial mediation was achieved. Participants in both samples showed improvement on all measures.

Limitations: This study relied on self-report measures of depressive severity and not clinical diagnosis. Results may not generalize to other populations of patients with chronic pain. There was no control condition in either study.

Conclusion: Increasing pain self-efficacy and decreasing a sense of helplessness are important treatment targets among IPRP participants who endorse symptoms of depression.