Single-blinded, randomised, parallel-group, controlled trial comparing the efficacy and cost-effectiveness of therapist- and self-guided internet-delivered behavioural activation versus treatment as usual for adolescents with mild to moderate depression: study protocol.

introductionThe number of adolescents seeking professional help for depression is increasing and, despite advances in treatment, large unmet treatment needs remain. In the current protocol, we describe the design and methodology of a randomised controlled trial (RCT) to evaluate the clinical efficacy of two forms of internet-delivered behavioural activation (I-BA), with and without therapist support, in reducing depressive symptoms, compared with treatment as usual (TAU). Secondary objectives include examining the 12-month maintenance of the treatment effects and conducting a health economic evaluation of the interventions. METHODS AND ANALYSIS: In this single-blinded RCT, we aim to include 215 participants aged 13-17 years with mild to moderate depression who will be randomised (1:1:1 ratio) to 10 weeks of either therapist-guided or self-guided I-BA, or TAU provided by regular mental health clinics. Data will be collected at baseline, weekly for the initial 10 weeks, post-treatment and at 3 and 12-month follow-ups. The primary endpoint is the 3-month follow-up. The primary outcome is blinded clinician-rated severity of depressive symptoms, measured by the Children's Depression Rating Scale-Revised. Treatment response is defined as a score of 'Much improved' or 'Very much improved' on the Clinical Global Impression-Improvement Scale, administered at the primary endpoint. Outcome assessors will be blinded to treatment conditions at all assessment points. A health economic evaluation of I-BA will be performed, both in the short term (primary endpoint) and the long term (12-month follow-up). ETHICS AND DISSEMINATION: Ethical approval was obtained from the Swedish Ethical Review Authority in June 2021. The final participant was enrolled on 3 May 2024 and expected to reach the primary endpoint by November 2024. The results of this study will be disseminated through publication in peer-reviewed journals, presented at conferences and communicated to healthcare providers and the public. TRIAL REGISTRATION NUMBER: NCT04977856.