School protective factors and adolescent mental health in Nigeria: an investigation of cumulative effects, buffering mechanisms, and gender differences

Abstract

Adolescent mental health disorders constitute a substantial public health concern in Nigeria, yet school-based protective factors remain understudied in sub-Saharan African contexts. This study examined cumulative associations between school protective factors and clinically diagnosed mental health outcomes, tested buffering effects against family adversity, and explored gender-differentiated pathways among Nigerian adolescents. A school-based cross-sectional survey was conducted using validated structured diagnostic instruments and standardised questionnaires. Data were analysed for 9,437 adolescents (mean age 15.61 years, 50.4% female) recruited through multistage stratified cluster sampling from 47 secondary schools across urban, semi-urban, and rural Lagos State. Mental health outcomes (depression, anxiety, behavioural disorders, substance use disorders, suicidal ideation) were assessed with the Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-Kid). School protective factors encompassed peer relationships, teacher support, school belonging, and absence of bullying. Adverse childhood experiences were measured using a standardised 10-item questionnaire. Multivariable logistic regression examined independent and cumulative protective associations, with interaction terms testing buffering effects and gender moderation. Clear dose–response associations emerged across all outcomes: each additional protective factor was associated with 42–54% lower odds of mental health conditions (adjusted odds ratios 0.46–0.58, all p < 0.001). Cumulative protection showed the strongest associations with suicidal ideation (OR = 0.48, 95% CI 0.41–0.57) and substance use disorders (OR = 0.46, 95% CI 0.37–0.58). School protective factors buffered the impact of adverse childhood experiences more strongly among high-ACE adolescents (interaction ORs 0.41–0.73, all p < 0.05). Among adolescents with high ACE exposure (≥ 3), depression prevalence decreased from 31.2% with low protection to 18.4% with high protection (41% relative risk reduction). Gender-stratified analyses suggested stronger protective associations for females with depression and for males with anxiety. School-based protective factors demonstrate robust dose-dependent associations with lower prevalence of clinically significant mental health conditions among Nigerian adolescents, with particularly strong buffering against family adversity. These cross-sectional findings provide initial evidence supporting school-centred mental health promotion strategies in sub-Saharan Africa. Longitudinal research is essential to establish temporal ordering, test causal mechanisms, and evaluate intervention effects. Not applicable.