Positive, but not negative, treatment outcome expectancies mediate the relation between depressive symptoms and treatment-related pain reduction

Previous research has shown that depression is associated with adverse recovery outcomes following work-related musculoskeletal injury. Treatment outcome expectancies have also been shown to predict recovery trajectories following musculoskeletal injury. The present study examined the role of positive and negative treatment outcome expectancies as mediators of the relation between depressive symptoms and treatment outcome for individuals receiving physical therapy for a musculoskeletal injury. The study sample consisted of 153 individuals who had sustained a work-related musculoskeletal injury to the back or neck within 6 months of enrolment. Participants completed self-report measures of depressive symptom severity, pain severity, and treatment outcome expectancies prior to treatment; pain severity was assessed again after 4 weeks of treatment. The results of this study were consistent with previous research showing significant relations between depressive symptom severity, pain severity and treatment outcome expectancies. Bootstrapping mediation analyses separately assessed the mediating roles of positive and negative treatment outcome expectancies on the relation between depressive symptoms and pain severity. Findings revealed that positive treatment outcome expectancies mediated the relation between depressive symptoms and pain severity, whereas negative treatment outcome expectancies did not. Discussion addresses potential pathways through which positive treatment outcome expectancies might influence pain outcomes. The findings suggest that intervention techniques aimed at increasing positive treatment outcome expectancies, rather than decreasing negative treatment outcome expectancies, might contribute to better recovery outcomes for individuals experiencing pain and depressive symptoms following a work-related musculoskeletal injury.