This interventional study is conducted with the goal of comparing the efficacy of traditional Buddhist mindfulness training versus secular mindfulness based cognitive therapy among patients with depressive disorders. We are also interested in studying how these interventions compare in terms of preventing further relapses of depression. Additionally, this study aims to identify factors that influence the efficacy of this intervention, such as self-report mindfulness, self-compassion, and religiosity.

This study has the following objectives:

1. To investigate whether traditional Buddhist mindfulness training is non-inferior to secular MBCT in reducing depressive symptoms and improving psychological wellbeing (primary outcomes)
2. To compare the effectiveness of the two interventions on self-compassion, mindfulness, and spirituality/religiosity (secondary outcomes)
3. To investigate whether self-compassion, mindfulness, and spirituality/religiosity mediate the effectiveness of the interventions
4. To investigate whether baseline spirituality/religiosity moderates the effectiveness of the interventions
5. To compare the effectiveness of the two interventions in preventing depressive relapse over 6 months and 12 months.

This will be a parallel group, randomized controlled trial conducted at Colombo North Teaching Hospital (CNTH), and the Faculty of Medicine, University of Kelaniya and involves interventions conducted over 4 months, followed by 12 months of follow-up. Patients with a history of depressive disorder will be recruited from the Psychiatry Clinic, Colombo North Teaching Hospital. Sample size, calculated for a non-inferiority trial design, is 30 in each group. Simple randomization and allocation concealment using sequentially numbered, opaque, sealed envelopes will be used. Both groups will undergo interventions over 8 weeks, with weekly 2-hour sessions. One group will undergo the novel intervention, i.e., traditional Buddhist mindfulness training. The other group will undergo MBCT. Primary outcomes will be depressive symptom severity (Beck Depression Inventory-II), Psychological wellbeing (WHO-5 Wellbeing Index), and the depressive relapse rate at 6 months and 1 year after completion of intervention. Secondary outcomes include mindfulness (Six-Facet Mindfulness Questionnaire), Self-compassion (Self-compassion scale - short form), Spirituality/religiosity (BENEFIT scale), and Acceptability/feasibility. To establish non-inferiority, the 95% CI of the mean difference will be compared against the non-inferiority margin. Moderator and mediation analyses will be conducted.

Inclusion Criteria:

• Age 18 or above
• Buddhist faith (Only Buddhists are selected as one of the interventions involves Buddhist teachings, and any recruited participant has a probability of being enrolled in the Buddhist mindfulness intervention)
• A history of one or more episodes of moderate or severe depression
• Currently having BDI-II score > 13, i.e., mild to moderate depressive symptoms

Exclusion Criteria:

• Currently having a severe depressive episode, according to the Composite International Diagnostic Interview (CIDI) Sinhalese version
• Currently having moderate to severe suicidal ideation (according to CIDI)
• Recent changes in antidepressant medication
• Unable to understand and communicate in Sinhalese

De-identified IPD will be shared publicly on Figshare.

Prior to the submission of the study findings to a journal

Public

As the study involves two psychological/behavioural interventions, it will not be possible to mask the participants, care providers or the investigators. However, most outcomes are based on self-report ratings, and the outcome at the end of the intervention (relapse of depression) will be assessed using telephone interviews by investigators blind to the participant's study arm.