Traditional Buddhist Mindfulness versus Secular Mindfulness-based Cognitive Therapy for Residual Depressive Symptoms in Patients Treated for Depressive Disorder: A Pilot Randomized Controlled Trial

Objectives To compare the efficacy, acceptability, and feasibility of traditional Buddhist mindfulness (TBM) versus secular mindfulness-based cognitive therapy (MBCT) for residual depressive symptoms, and to examine whether TBM is non-inferior to MBCT in improving depressive symptoms and psychological wellbeing. Methods In this pilot randomized controlled trial, Buddhist adults with residual depressive symptoms (Beck Depression Inventory–II [BDI-II] score > 13) receiving outpatient antidepressant treatment were randomized to an 8-week group-based TBM or MBCT intervention. Primary outcomes were depressive symptoms (BDI-II) and psychological wellbeing (WHO-5 Well-Being Index). Secondary outcomes included mindfulness, self-compassion, and perceived benefits from religiosity/spirituality. Primary analyses followed the intention-to-treat principle. Non-inferiority margins were prespecified at 2.5 BDI-II points and 1.25 WHO-5 points. Results Sixty-six participants were randomized (TBM = 34; MBCT = 32). Both interventions produced significant within-group improvements. Mean BDI-II scores decreased by 13.1 points in TBM ( p  < .001; Cohen’s d  = 0.93) and 12.9 points in MBCT ( p  < .001; d  = 1.15). WHO-5 scores increased by 6.8 points in TBM ( p  < .001; d  = 0.93) and 6.9 points in MBCT ( p  < .001; d  = 0.95). Between-group differences were not statistically significant, and non-inferiority of TBM was not demonstrated (BDI-II: Mdiff = − 0.16, 95% CI − 5.4 to 5.1; WHO-5: Mdiff = − 0.2, 95% CI − 3.2 to 2.8). Mindfulness and self-compassion increased in both groups, while religiosity/spirituality increased only in TBM. Conclusions Both TBM and MBCT were associated with large, clinically meaningful improvements and comparable acceptability. TBM’s selective effect on religiosity/spirituality highlights its cultural relevance and supports further evaluation in larger trials. Pre-registration: This study was registered in the Clinical Trial Registry ([Blinded for Review]) on 13/06/2024.