The effect of mindfulness-based cognitive therapy on rumination and a task-based measure of intrusive thoughts in patients with bipolar disorder

Background: Preliminary evidence suggests that Mindfulness-Based Cognitive Therapy (MBCT) is a promising treatment for bipolar disorder (BD). A proposed working mechanism of MBCT in attenuating depressive symptoms is reducing depressive rumination. The primary aim of this study was to investigate the effect of MBCT on self-reported trait depressive rumination and an experimental state measure of negative intrusive thoughts in BD patients. Exploratively, we investigated the effect of MBCT on positive rumination and positive intrusive thoughts. Methods: The study population consisted of a subsample of bipolar type I or II patients participating in a multicenter randomized controlled trial comparing MBCT+treatment as usual (TAU) (N=25) to TAU alone (N=24). Trait depressive rumination (RRS brooding subscale) and intrusive thoughts (breathing focus task (BFT)) were assessed at baseline (full subsample) and post-treatment (MBCT+TAU; n=15, TAU; n=15). During the BFT, participants were asked to report negative, positive and neutral intrusive thoughts while focusing on their breathing. Results: Compared to TAU alone, MBCT+TAU resulted in a significant pre- to post-treatment reduction of trait depressive rumination (R^2=.16, F(1, 27)=5.15, p=0.031; medium effect size (f^2=0.19)) and negative intrusive thoughts on the BFT (R^2=.15, F(1, 28)=4.88, p=0.036; medium effect size (f^2=0.17)). MBCT did not significantly change positive rumination or positive intrusive thoughts. Conclusions: MBCT might be a helpful additional intervention to reduce depressive rumination in BD which might reduce risk of depressive relapse or recurrence. Considering the preliminary nature of our findings, future research should replicate our findings and explore whether this reduction in rumination following MBCT indeed mediates a reduction in depressive symptoms and relapse or recurrence in BD. Keywords: Bipolar disorder, Mindfulness-based cognitive therapy, Breathing focus task, Depressive rumination, Positive rumination, Intrusive thoughts