Evaluating the Effectiveness of Cognitive Behavioural Therapy for Adolescent Depression in Secondary Schools in Ogun State

Adolescent depression in Nigerian secondary schools is undertreated, and building evidence for the effectiveness of structured cognitive behavioural therapy delivered in school counselling settings is essential for informing policy on school mental health services. This study evaluated the effectiveness of a school-based CBT intervention for adolescent depression in four secondary schools in Abeokuta, Ogun State, South West Nigeria. A pre-test post-test quasi-experimental design was employed. Fifty adolescents with clinically significant depression (scoring above 20 on the Reynolds Adolescent Depression Scale) were assigned to a 10-session group CBT programme (n=25) or a waitlist control group (n=25). The CBT programme was delivered by trained school counsellors following a structured protocol. Post-intervention assessments were conducted at 8 weeks and 3 months. Results showed significant reductions in depression scores in the CBT group at 8 weeks (t = 6.24, p < 0.001, Cohen's d = 1.76) compared to no significant change in the control group. Improvement was maintained at 3-month follow-up. Academic attendance improved significantly in the CBT group (p < 0.01). No adverse events were observed. Counsellor fidelity to the CBT protocol was rated above 80 percent across all sessions. The study provides evidence supporting school-based CBT as an effective and feasible approach for adolescent depression in Nigerian secondary schools and recommends its formal integration into the school counsellor training curriculum in Ogun State. Keywords: CBT, adolescent depression, school counselling, Ogun State, intervention effectiveness