Mindfulness Interventions for Obsessive-Compulsive and Related Disorders: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Mindfulness interventions (MIs) emphasize living in the present moment without being judgmental of one's feelings and sensations. We aimed to evaluate the effectiveness of MIs, including both mindfulness-based and mindfulness-informed interventions, in reducing overall obsessive-compulsive and related disorders (OCRDs) severity and comorbid depression at post-treatment and in the long-term. The potential contribution of methodological variables moderating the effectiveness of MIs was examined. Five databases (Medline, PsychInfo, Embase, Web of Science, Cochrane Register of Controlled Trials) were searched until May 2022. The pooled standardized mean difference was calculated using random effect models. Twenty-six studies with 1,281 participants were included. We found moderate to large reductions in overall OCRDs severity in favor of MIs at post-treatment (SMD ranging between -0.62 and -1.52, 95% CI: -2.02 to -0.22). MIs were associated with small reductions of depression in people with OCD (SMD = -0.30 and -0.52, 95% CI: -0.68 to -0.09) and obsessions (SMD = -0.32, 95% CI: -0.65 to -0.01) at post-treatment but these effects were not sustained at follow-up. Meta-regression analyses showed that Acceptance and Commitment Therapy (ACT) and Mindfulness-Based Cognitive Therapy (MBCT) appeared to be effective in treating OCD and/or depressive symptoms in these patients. Lower income countries contributed larger effect sizes. Our findings provide first evidence of the effectiveness of MIs in reducing OCRDs severity which require further exploration from high quality RCT studies with embedded qualitative research.