The Mechanisms of Mindfulness-Based Stress Reduction and Mindfulness-Based Cognitive Therapy for Cancer Patients and Survivors: A Systematic Review.

While many systematic reviews have focused on relationships between mindfulness-based interventions (MBIs) and myriad outcomes, no systematic review has examined the mechanisms through which MBIs affect outcomes in the context of cancer. A systematic review was conducted of experimental or quasi-experimental studies that longitudinally examined potential mechanisms of the effects of either mindfulness-based stress reduction (MBSR) or mindfulness-based cognitive therapy (MBCT) interventions with adult cancer patients and survivors. Searches were conducted in Pubmed, APA PsycInfo, Cumulated Index to Nursing and Allied Health Literature, Cochrane, and Scopus databases up to May 2022. The results of included studies were narratively synthesized and studies were graded for quality using a rubric tailored to mediational intervention studies. Of 156 experimental or quasi-experimental studies that implemented either MBSR or MBCT interventions with adult cancer patients and survivors, only 13 longitudinally tested for mediators (e.g., changes in mindfulness, rumination, and self-compassion) of intervention effects. Most studies lacked a strong, active control group and most (10/13) were of medium quality. Results on mindfulness as a mediator of intervention effects were inconclusive, and many other mediators were only tested within a single study. Methodological limitations, including lack of strong comparison groups and theoretical frameworks and inconsistent conceptualizations of mindfulness, preclude drawing strong conclusions from the current body of evidence. MBIs may operate differently for cancer patients/survivors, highlighting the importance of continuing to test for mediation within this population.