Effectiveness of a Digital Mental Health Intervention for Adolescent Depression in Secondary Schools Across Three Nigerian Geopolitical Zones: A Cluster RCT

Digital mental health interventions offer scalable solutions for adolescent depression in settings where specialist psychiatric services are unavailable, yet evidence from Nigerian schools is entirely absent. This cluster randomized controlled trial evaluates the effectiveness of a locally adapted digital mental health intervention for adolescent depression delivered via mobile application in secondary schools across South West, North Central, and South East Nigeria. Forty secondary schools (20 intervention, 20 control) will be cluster-randomized across Oyo, Niger, and Anambra States. The intervention is an eight-session, structured psychoeducation and problem-solving application developed through co-design with Nigerian adolescents and mental health professionals. The primary outcome will be change in PHQ-A scores at 12 weeks. Secondary outcomes include help-seeking intention, mental health literacy, and functional impairment. Implementation outcomes including reach, adoption, fidelity, and sustainability will be assessed using the RE-AIM framework. Multilevel mixed-effects models will account for school-level clustering. This study constitutes an original contribution to digital mental health implementation science in Nigeria, generating the first cluster RCT evidence on school-based digital mental health intervention for adolescents across multiple geopolitical zones. Keywords: digital mental health, adolescent depression, cluster RCT, secondary schools, Nigeria