RT Journal Article SR Electronic T1 School-based mindfulness training in early adolescence: what works, for whom and how in the MYRIAD trial? JF Evidence Based Mental Health JO Evid Based Ment Health FD BMJ Publishing Group Ltd, Royal College of Psychiatrists and British Psychological Society SP 117 OP 124 DO 10.1136/ebmental-2022-300439 VO 25 IS 3 A1 Jesus Montero-Marin A1 Matthew Allwood A1 Susan Ball A1 Catherine Crane A1 Katherine De Wilde A1 Verena Hinze A1 Benjamin Jones A1 Liz Lord A1 Elizabeth Nuthall A1 Anam Raja A1 Laura Taylor A1 Kate Tudor A1 MYRIAD Team A1 Sarah-Jayne Blakemore A1 Sarah Byford A1 Tim Dalgleish A1 Tamsin Ford A1 Mark T Greenberg A1 Obioha C Ukoumunne A1 J Mark G Williams A1 Willem Kuyken YR 2022 UL http://mentalhealth.bmj.com//content/25/3/117.abstract AB Background Preventing mental health problems in early adolescence is a priority. School-based mindfulness training (SBMT) is an approach with mixed evidence.Objectives To explore for whom SBMT does/does not work and what influences outcomes.Methods The My Resilience in Adolescence was a parallel-group, cluster randomised controlled trial (K=84 secondary schools; n=8376 students, age: 11–13) recruiting schools that provided standard social–emotional learning. Schools were randomised 1:1 to continue this provision (control/teaching as usual (TAU)), and/or to offer SBMT (‘.b’ (intervention)). Risk of depression, social–emotional–behavioural functioning and well-being were measured at baseline, preintervention, post intervention and 1 year follow-up. Hypothesised moderators, implementation factors and mediators were analysed using mixed effects linear regressions, instrumental variable methods and path analysis.Findings SBMT versus TAU resulted in worse scores on risk of depression and well-being in students at risk of mental health problems both at post intervention and 1-year follow-up, but differences were small and not clinically relevant. Higher dose and reach were associated with worse social–emotional–behavioural functioning at postintervention. No implementation factors were associated with outcomes at 1-year follow-up. Pregains−postgains in mindfulness skills and executive function predicted better outcomes at 1-year follow-up, but the SBMT was unsuccessful to teach these skills with clinical relevance.SBMT as delivered in this trial is not indicated as a universal intervention. Moreover, it may be contraindicated for students with existing/emerging mental health symptoms.Clinical implications Universal SBMT is not recommended in this format in early adolescence. Future research should explore social−emotional learning programmes adapted to the unique needs of young people.Data are available upon reasonable request. The data and codebook from the MYRIAD Trial are available from Prof Kuyken (willem.kuyken@psych.ox.ac.uk) upon request (release of data is subject to an approved proposal and a signed data access agreement).