Symptoms of depression and stress mediate the effect of pain on disability

The mechanism or mechanisms involved in the development of pain-related disability in people with low back pain is unclear. Psychological distress has been identified as one potential pathway by which an episode of pain influences the development of persistent disabling symptoms; however, the relationship has not been formally investigated. This study investigated the causal relationship between pain and disability via psychological distress (and its components depression, stress, and anxiety) by using mediation path analysis. The study sample included 231 participants with subacute low back pain (6 to 12 weeks' pain duration) who had been recruited for an exercise-based randomised, controlled trial. All participants completed self-report assessments of pain (0-10 numerical rating scale), disability (Roland Morris Disability Questionnaire), and psychological distress (Depression Anxiety and Stress Scale) at baseline and again at 2 follow-up time points (6 and 12 weeks after baseline). The results of the mediation analysis suggest that approximately 30% of the relationship between subacute pain and later disability is dependent on the level of patients' psychological distress. The finding that psychological distress only partially (30%) mediated the pain-disability relationship indicates that other factors should also be explored. Further analysis into the components of psychological distress revealed that the symptoms of depression and stress, but not anxiety, are responsible for mediation of the pain-disability relationship. These findings provide an opportunity to decrease the risk of long-term disability through early identification and management of depressive and stress symptoms.