Exploring implementation experiences following WHO mhGAP training in primary health care in Lagos, Nigeria: a CFIR-guided evaluation

The WHO’s Mental Health Gap Action Programme (mhGAP) offers an evidence-based framework to integrate mental health into primary health care (PHC), especially in low- and middle-income countries (LMICs). In Lagos State, Nigeria, the mhGAP-Intervention Guide (mhGAP-IG) was delivered to over 850 PHC workers across 57 facilities through the Mental Health in Primary Care (MeHPriC) initiative. This study explores the implementation experiences of frontline workers and stakeholders three months post-training. We conducted 12 focus group discussions and 10 key informant interviews with a purposive sample of PHC workers and system actors, analyzing data using the Consolidated Framework for Implementation Research (CFIR). Five major themes emerged: enhanced provider confidence and role expansion; attitudinal shifts and stigma reduction; supervision and peer support as enablers; systemic barriers such as medication shortages and infrastructure gaps; and grassroots adaptations to sustain delivery. WhatsApp-based peer networks and provider-led innovations were key facilitators. While mhGAP training improved competencies and reduced stigma, systemic constraints hindered sustainability. Strengthening supervision, medication supply chains, and acknowledging provider agency are critical for successful scale-up. These findings inform future efforts to embed mental health into PHC systems in LMICs through locally grounded and system-sensitive implementation strategies.