Scaling mental health care in Nigeria: Impact of WHO mhGAP training under the MeHPriC program on knowledge, attitudes, and practices of primary health care workers in Lagos State - A pre-post mixed-methods study.

The growing burden of mental, neurological and substance use (MNS) disorders in low-resource settings has prompted efforts to integrate mental health into primary health care (PHC). This study evaluated the implementation and outcomes of a large-scale mhGAP training initiative under the Mental Health in Primary Care (MeHPriC) program in Lagos State, Nigeria. A total of 852 PHC workers from 57 facilities completed a 5-day mhGAP training and a 1-day refresher session. Using a pre-post mixed-methods design, we assessed changes in knowledge, stigma, clinical practice and self-efficacy, with follow-up at five months. Quantitative findings revealed significant improvements in knowledge and attitudes, with enhanced clinical practice reported by 69.1% of participants. Supervision, knowledge gains and self-efficacy emerged as predictors of improved practice. Qualitative data, analyzed using the Consolidated Framework for Implementation Research (CFIR), highlighted increased confidence, reduced stigma and the enabling role of supervision and peer support, alongside persistent barriers such as medication stock-outs and limited referral networks. The study offers robust evidence for the effectiveness of task-sharing approaches when supported by contextual adaptation and system-level readiness. The MeHPriC model demonstrates that government-led mhGAP scale-up in PHC is both feasible and impactful, offering a replicable pathway for mental health integration in other LMICs.