Inpatient multimodal rehabilitation and the role of pain intensity and mental distress on return-to-work: causal mediation analyses of a randomized controlled trial

Objective: Studies suggest that symptom reduc-tion is not necessary for improved return-to-work after occupational rehabilitation programmes. This secondary analysis of a randomized controlled trial examined whether pain intensity and mental dist-ress mediate the effect of an inpatient programme on sustainable return-to-work. Methods: The randomized controlled trial compared inpatient multimodal occupational rehabilitation (n = 82) with outpatient acceptance and commit-ment therapy (n= 79) in patients sick-listed due to musculoskeletal and mental health complaints. Pain and mental distress were measured at the end of each programme, and patients were followed up on sick-leave for 12 months. Cox regression with an inverse odds weighted approach was used to assess causal mediation. Results: The total effect on return-to-work was in favour of the inpatient programme compared with the control (hazard ratio (HR) 1.96; 95% confi-dence interval (95% CI) 1.15-3.35). There was no evidence of mediation by pain intensity (indirect effect HR, 0.98; 95% CI, 0.61-1.57, direct effect HR, 2.00; 95% CI, 1.02-3.90), but mental distress had a weak suppression effect (indirect effect HR, 0.89; 95% CI, 0.59-1.36, direct effect HR, 2.19; 95% CI, 1.13-4.26). Conclusion: These data suggest that symptom reduction is not necessary for sustainable return -to-work after an inpatient multimodal occupational rehabilitation intervention.