Synchronous online group MBCT vs guided asynchronous iMBCT in depressed sample: randomized clinical trial with a 3-month follow-up

Background Online Mindfulness-Based Cognitive Therapy (iMBCT) is a promising intervention for mental health, but its effectiveness in reducing depressive symptoms remains underexplored. While key mechanisms of change have been identified in traditional MBCT, their role in online delivery formats needs further investigation. Methods In this randomized clinical trial, 170 individuals with mild to moderate depression were assigned to a 6-week synchronous iMBCT group (n = 58), asynchronous iMBCT group (n = 59), or waitlist control (n = 53). Depression, anxiety, mindfulness, cognitive fusion, rumination, self-compassion, resilience, and experiential avoidance were assessed at baseline, post-treatment, and 3-month follow-up. Results Posttest assessments were completed by 42 participants (72%) in the synchronous group, 32 (54%) in the asynchronous group, and 51 (96%) in the waitlist control condition. Both iMBCT formats significantly reduced depressive symptoms compared to the control group, with sustained effects at follow-up. Mindfulness and cognitive defusion emerged as significant mediators, explaining 52% of the variance in the post-treatment depression severity. Additionally, participants in both interventions showed decreased rumination and anxiety, and increased self-compassion and resilience - effects maintained at follow-up. Conclusions Synchronous and asynchronous iMBCT formats are effective in reducing depressive symptoms and enhancing psychological well-being. These findings support the use of online mindfulness-based interventions as scalable, accessible alternatives to traditional therapy.