Rumination and Self-Compassion Moderate Mindfulness-Based Cognitive Therapy for Patients With Recurrent and Persistent Major Depressive Disorder: A Controlled Trial.

Background: Mindfulness-based cognitive therapy (MBCT) is effective in reducing depressive symptoms in patients with major depressive disorder (MDD). Understanding for whom and how MBCT works may allow for improvements in treatment allocation and effectiveness. In this study, our aim was to investigate depressive rumination, content-independent perseverative thinking, mindfulness skills, and self-compassion as potential moderators and mediators of MBCT.

Methods: In this non-randomized controlled trial, patients with persistent (n = 53) or recurrent MDD with (n = 31) or without (n = 51) a current depressive episode were assigned to an intervention (MBCT plus treatment as usual [TAU], n = 94) or control group (TAU only, n = 40) based on the time between the date of inclusion and the start of MBCT. Assessments were carried out before, halfway, and after 8 weeks of MBCT + TAU or TAU. Latent growth models were employed to examine moderation, while cross-lagged structural equation models were used to assess the mediating effects of several possible mediators of MBCT-induced change in depressive symptoms and overall functional impairment.

Results: MBCT + TAU was more effective in reducing depressive symptoms (and overall functional impairment than TAU with a medium [d = -0.54] and small [d = 0.44] effect size, respectively). Higher baseline levels of rumination and perseverative thinking and lower levels of self-compassion moderated the effect of MBCT on depressive symptoms and overall functional impairment. Task-based negative intrusive thoughts moderated the effects of MBCT on overall functional impairment. No mediators were established, particularly due to a lack of effect of MBCT on all assessed mediators at mid-treatment. For interpretative purposes, a sample split (based on Johnson-Newman values) showed moderate-to-large effects in depressive symptom reduction for those with high rumination, high perseverative thinking, and low self-compassion, while negative-to-small nonsignificant effects were found for the opposite traits.

Conclusion: In the future, MBCT allocation based on levels of rumination and self-compassion might lead to a more efficient reduction in depressive symptoms. Directions for mediation analysis within the context of MBCT for depression are discussed. Preregistration: This study was initially preregistered in the Dutch National Trial Register (NL7842). However, due to the NTR no longer being available since June 2022, the trial was reregistered at ClinicalTrials.gov (NCT05802966, dd 09-Apr-2023). The statistical analysis plan was adjusted after the start of the trial but before the finalization of data collection (NCT05802966; ClinicalTrials.gov).