Efficacy and Cost-effectiveness of Internet-delivered CBT for Adolescents With Depression

Primary and secondary objectives Primary objective: 1\. To determine the clinical efficacy of Guided and Self-guided ICBT for depression for reducing depressive symptom severity (as measured by the CDRS-R (27) in adolescents with mild and moderate major depressive disorder (MDD), compared with an active control intervention (treatment as usual within primary or secondary child and adolescent mental health care). The primary endpoint is the follow-up 3 months post-treatment. Secondary objectives: 1. To establish the 12-month durability of the treatment effects. 2. To conduct a health-economic evaluation of guided ICBT for depression and self-guided ICBT for depression, compared with TAU, from multiple perspectives, both in the short term (primary endpoint) and the long term (12-month follow-up). 3. To investigate potential mediators behind a potential treatment effect of ICBT. Research questions: 1. Is guided and self-guided ICBT more efficacious than TAU in regard to the reduction of depressive symptoms? 2. Is guided and self-guided ICBT more cost-effective than TAU? 3. Is self-guided ICBT more cost-effective than guided ICBT? 4. Are the therapeutic gains of ICBT maintained long term (i.e., 1 year after the intervention)? 5. Do changes in activation and avoidance (BADS) mediate changes at post-treatment in self-reported depressive symptoms (QIDS-A-17) in adolescents receiving ICBT (with or without therapist support), but not in the control group (treatment as usual)?