Supplementary Material for: A Tale of two Treatments: A randomized controlled trial of mindfulness or cognitive-behaviour therapy delivered online for people with rheumatoid arthritis

Introduction: This study aims to determine the relative efficacy of mindfulness-based stress reduction (MBSR) or cognitive-behaviour therapy (CBT) in comparison to a wait-list control (WLC) for people with rheumatoid arthritis (RA). Participants completed assessments before and after treatment and at 6-month follow-up. Methods: Two-hundred and sixty-nine participants with RA were recruited and randomized in a 2:2:1 ratio to MBSR: CBT: WLC. Participants completed a semi-structured clinical interview for depression and were stratified for history of recurrent depression. We measured the primary outcome of pain interference, and pain severity, depression, anxiety, functional ability, and fear of progression. We predicted that MBSR and CBT would result in improvements compared to WLC . We also predicted that those with a history of recurrent depression would benefit more from MBSR than CBT for depression. Results: MBSR and CBT were equally efficacious in reducing pain interference compared to WLC. Similar results were found for depression. MBSR demonstrated superior outcomes to CBT for fear of progression at post-treatment and functional ability at 6-month follow-up. CBT only was better than WLC for pain severity at 6-month follow-up. Depressive status did not moderate the efficacy of treatment. Conclusions: MBSR and CBT resulted in statistically and clinically significant changes in pain interference compared to WLC. MBSR was more efficacious than CBT for functional ability and fear of progression, while CBT showed superiority for pain severity. The effect sizes were comparable to those achieved with face-to-face interventions, confirming both online treatments are effective for people with RA.