Adolescents and carers using mindfulness Therapy To END depression (ATTEND): study protocol for a parallel randomised controlled superiority trial of Mindfulness for Adolescents and Carers (MAC) for depression among young people aged 15 to 18 years old with an embedded economic evaluation

Background Mindfulness-based cognitive therapy (MBCT) is a group intervention recommended by NICE for adults who have experienced recurrent depression but is untested for adolescents. MBCT aims to teach people to recognise early indicators of depression, to avoid repetitive thinking patterns that make relapse more likely, and to respond to stressors in ways that protect mental health. We developed Mindfulness for Adolescents and Carers (MAC), a version of MBCT adapted to be more engaging for young people. MAC includes a parallel programme aimed at strengthening family support and parental mental health and may help minimise the developmental impact of functional impairment during the transition to adulthood. The primary aim of this trial is to evaluate the clinical- and cost-effectiveness of MAC in 15- to 18-year-olds at risk of repeated depressive episodes in the UK. Methods ATTEND will be a two-arm, pragmatic, parallel-group, superiority, individually randomised controlled hybrid type I trial of clinical and cost-effectiveness. We will randomise 480 15SAP-18-year-olds who have received at least one previous evidence-based intervention for depression or anxiety, yet continue to experience symptoms of depression, to either MAC plus treatment as usual (TAU) or TAU alone. MAC will be delivered by trained professional facilitators to groups of 6 to 14 young people, with a parallel but optional group for parents/carers. The primary outcome will use an area under analysis of the mean difference in the Short Mood and Feelings Questionnaire, which will be collected fortnightly over a 12-month follow-up period. Secondary outcomes will be measured in both young people and their parents/carers, including depression, anxiety symptoms, quality of and coping with life, and the quality of parent-child relationships at baselines, 14 weeks and 12 months post randomisation. Parental mental health will also be measured fortnightly. After the primary main and mediation analyses have been completed, the de-identified individualised patient data, data dictionaries and statistical analysis code underlying published results will be as accessible to other researchers with a methodologically sound proposal via the ATTEND Core Team using the standard ATTEND Publication Proforma. The protocol and statistical analysis plans will also be available via the study website. Discussion This study will provide important information about whether MAC is a clinically and cost-effective intervention to reduce depression symptom severity and chronicity in adolescents. Trial registration {4} International Standard Randomised Controlled Trials, identifier: ISRCTN 17687131 . Registered on 15 August 2024.