Effectiveness of a School-Based Mental Health Literacy Intervention on Attitudes Toward Mental Illness Stigmatization Among Secondary School Students in Ogun State, Nigeria

Background: Adolescents experience significant mental health challenges, and stigma remains a major barrier to help-seeking and psychosocial well-being. School-based mental health literacy (MHL) interventions have been identified as effective strategies for improving knowledge and reducing stigmatizing attitudes. However, evidence on culturally adapted MHL interventions in Nigerian secondary schools remains limited. Aim: This study examined the effectiveness of a Mental Health Literacy (MHL) intervention in improving secondary school students’ attitudes toward mental illness stigmatization in Ogun State, Nigeria. Method: A two-group quasi-experimental pretest–posttest design was employed among 155 senior secondary school students. Participants were assigned to intervention (n = 78) and control (n = 77) groups. Attitudes were measured using a 20-item Likert-type scale (1–4), with normalized mean scores categorized as negative (1.00–2.50) or positive (2.51–4.00). Data were collected at baseline (P₀), six weeks (P₁), and twelve weeks (P₂) post-intervention. Descriptive statistics and paired-samples t-tests were used for analysis, with effect size calculated using Cohen’s d at a 5% significance level. Results: At baseline, both groups demonstrated predominantly negative attitudes toward mental illness. The intervention group showed significant improvement in mean attitude scores at six weeks and twelve weeks post-intervention (p < 0.001), with a large effect size (d = 0.95). The proportion of students exhibiting positive attitudes increased substantially by twelve weeks. In contrast, the control group demonstrated minimal and non-significant changes (p = .582). Conclusion: The culturally adapted MHL intervention significantly reduced stigmatizing attitudes toward mental illness among secondary school students. Integrating structured mental health literacy programmes into school curricula may promote sustained stigma reduction and support early help-seeking behaviors among adolescents. Recommendations: School health programmes should incorporate nurse-led mental health literacy education using culturally relevant and interactive approaches. Policymakers should support curriculum integration of MHL initiatives to strengthen adolescent mental health promotion efforts. Keywords: Mental health literacy; Stigma; Adolescents; School-based intervention; Mental illness; Attitude change; Nigeria; Quasi-experimental study, Students