iCAN: A chatbot-assisted mobile aftercare app for adolescents and young adults with depression – Protocol for a multicenter mixed-methods randomized controlled trial (Preprint)

BACKGROUND Depression is prevalent among adolescents and young adults and often requires aftercare following inpatient treatment. Although effective outpatient aftercare exists, many patients face difficulties in maintaining treatment gains and remain without professional support after being discharged. Digital mental health interventions hold promise for bridging this care gap; however, evidence of their effectiveness is limited. OBJECTIVE This protocol outlines a study evaluating the effectiveness, cost-effectiveness, and implementation of a chatbot-assisted smartphone intervention (iCAN) designed to support youth following inpatient treatment for depression. METHODS This is a prospective, two-armed, mixed-methods randomized controlled trial. The targeted sample size is n = 368 patients aged 13–25 years with depressive disorders who were receiving inpatient treatment and, additionally, n = 18 healthcare providers. Participants in the intervention group received care as usual plus an e-coach-guided intervention for 90 days, whereas the control group received care as usual only. Assessments were conducted at baseline and 6 weeks, 3 months, and 6 months after randomization. The primary outcome is clinician-rated severity of depression symptoms. Secondary outcomes include remission rates, general psychopathology, quality of life, uptake of aftercare services, cost-effectiveness, mechanisms of action, as well as acceptability, and usability. Outcome evaluation will use linear mixed models based on the intention-to-treat principle, and process evaluation will be conducted via content analysis. RESULTS We enrolled n = 228 patients from 31 hospitals across Germany between November 2023 and December 2024. Data collection (6 months follow-up) was completed June 2025. Data analysis is currently in progress, with the first results expected to be published by the end of 2026. CONCLUSIONS This study will provide evidence for the effectiveness and cost-effectiveness of a guided digital mental health intervention for post-discharge aftercare of youth treated for depression in an inpatient setting. It will offer insights into the implementation of the intervention in routine care. If proven effective, iCAN may serve as a blueprint for remote aftercare for young people with depression. CLINICALTRIAL This trial is registered in the German register for clinical trials (DRKS-ID: DRKS00032966)