Objectives: To evaluate the clinical- and cost-effectiveness of two delivery formats of mindfulness-based cognitive therapy (MBCT) - (i) MBCT delivered through eight videoconference group sessions (group MBCT), and (ii) MBCT delivered through a self-help manual plus three low-intensity videoconference group support sessions (supported MBCT self-help) - when added to treatment as usual (TAU; mental health outpatient care), compared with TAU alone, in patients with recurrent depression in partial remission. We will identify potential predictors and moderators of response and examine psychological mechanisms of change. Study design: Multicentre randomised controlled trial, with pre-post, 6- and 12-months follow-ups. Centres: Parc Sanitari Sant Joan de Déu (St. Boi de Llobregat), Hospital Universitario Miguel Servet (Zaragoza), and Hospital del Mar (Barcelona). Participants: Adult patients (n=315) with recurrent depression in partial remission will be randomly assigned to group MBCT, supported MBCT self-help, or TAU. Primary outcome: time from randomisation to depressive relapse/recurrence at 12-month follow-up (DSM-5). Secondary outcomes: residual symptoms, well-being, quality of life, costs, and quality-adjusted life years. Process measures: rumination, mindfulness, decentering, affectivity, and self-compassion. Main statistical analyses: Hazard ratios will be calculated using survival analysis. Secondary outcomes, predictors, and moderators will be tested using regression-based approaches. Incremental cost-effectiveness ratios from healthcare system and societal perspectives will be estimated, alongside mediation analyses. Expectations and acceptability will be evaluated using qualitative methods. Conclusions: This study will inform the implementation of two accessible MBCT formats in Spain for preventing depressive relapse/recurrence. The use of different delivery formats will provide information on effectiveness, scalability, and value for money.

The BECOME trial was developed to fill an important evidence gap on whether Mindfulness-Based Cognitive Therapy (MBCT) is clinically effective and cost-effective for preventing relapse and recurrence of depression when delivered within the Spanish National Health System (NHS). While MBCT has strong evidence as an alternative to maintenance antidepressant medication (m-ADM) for people with recurrent depression, most of this research has been conducted outside Spain and has not been confirmed in a sufficiently powered, multicentre randomized controlled trial in the Spanish setting. This gap is especially relevant in the post-COVID-19 period, when depressive disorders have increased in prevalence and severity, adding pressure to already overstretched public mental health services. Recurrent depression also carries a high social and economic burden in Spain, so identifying interventions that can reduce relapse while remaining feasible and sustainable for the NHS is a public health priority. Most prior studies have focused on face-to-face MBCT and have given limited attention to implementation constraints in publicly funded systems. In addition, many patients report concerns about long-term antidepressant use (e.g., side effects and adherence difficulties) and often prefer psychological approaches, highlighting the need to evaluate acceptable and accessible alternatives such as MBCT. By comparing videoconference-delivered group MBCT and supported MBCT self-help against treatment as usual (TAU), this study aims to provide pragmatic evidence on whether different MBCT delivery formats can broaden access to relapse-prevention care while preserving clinical benefit and good value for money in routine services. The trial will also assess outcomes from both healthcare and societal perspectives, which is important given the significant indirect costs of recurrent depression in Spain, including work disability and reduced productivity. As digitally supported care becomes more common, rigorous evaluation of its clinical and economic impact is essential to ensure that digital delivery improves outcomes and delivers measurable public health value.

Inclusion Criteria:

• Age over 18.
• Diagnosis of recurrent major depressive disorder, with ≥ 2 previous major depressive episodes (MDD).
• Current partial remission (no current depressive episode; a score ≥8 on the HDRS).
• Internet access (via smartphone or personal computer).
• Spanish literacy (spoken and written).

Exclusion Criteria:

• Current or past psychosis, bipolar disorder, a history of schizophrenia, schizoaffective disorder, organic mental disorder, current severe substance abuse, organic brain damage, pervasive developmental delay, persistent antisocial behaviour, recent (in past 3 months) self-injury requiring clinical management or therapy according to medical records and clinical judgment.
• Formal concurrent structured psychotherapy during the intervention period.
• No experience in the use of new technologies (smartphones or computers).
• Having completed a mindfulness-based structured training and/or extensive meditation experience (i.e., previous participation in meditation retreats (≥1) or regular (≥ weekly) meditation practice) in the previous year, or intending to commence meditation retreats or meditation practice during the study.