Randomised Controlled Trial of School-Based Positive Psychology Intervention for Enhancing Well-Being and Reducing Internalising Problems in Adolescents in Ogun State

Positive psychology interventions offer a proactive alternative to traditional problem-focused approaches in school counselling, yet their effectiveness within Nigerian adolescent populations has not been tested through rigorous randomised designs. This study conducted a randomised controlled trial (RCT) of a school-based positive psychology intervention for enhancing psychological well-being and reducing internalising problems among adolescents in Ogun State, South West Nigeria. A cluster-randomised controlled trial design was used, with twelve secondary schools randomised to intervention and wait-list control conditions. A total of 480 students participated across the two conditions. The twelve-week intervention programme incorporated gratitude practices, strengths identification, goal-setting, and positive relationship-building activities facilitated by trained school counsellors. The Warwick-Edinburgh Mental Well-Being Scale (WEMWBS), the Strengths and Difficulties Questionnaire (SDQ), and the Rosenberg Self-Esteem Scale were administered at baseline, post-intervention, and twelve-week follow-up. Multilevel modelling was used to account for clustering. Findings demonstrated significant intervention effects on psychological well-being and self-esteem at post-intervention, with gains maintained at follow-up. Internalising problems showed significant reduction in the intervention condition. Counsellor fidelity to the intervention protocol was a significant moderator of outcomes. The study provides the first RCT evidence for a school-based positive psychology intervention in Nigeria, establishing the programme as an evidence-based counselling practice. Keywords: positive psychology, randomised controlled trial, school-based intervention, well-being, Ogun State.