Fidelity and feasibility of a pilot implementation of adapted WHO digital interventions to scale up mental health in Nigerian primary care: A mixed-methods process evaluation.

To address challenges in the real-world implementation of digital health for mental healthcare in Nigeria, this study conducted a process evaluation of five World Health Organization-recommended digital tools within a state-wide primary health care program in Lagos. Employing a convergent mixed-methods design across five facilities, we measured implementation fidelity through observation and platform analytics, and assessed stakeholder perceptions via validated surveys and interviews. The findings revealed a sharp divergence in success. Administrative tools that streamlined workflows, such as drug stock notification and automated client reminders, achieved high fidelity (>90% adherence). In contrast, clinical tools that altered provider-patient interactions, including a decision support app and a client helpline, demonstrated low fidelity (<66% adherence). Qualitative analysis attributed this gap to the successful tools' seamless workflow integration versus the clinical tools' disruption of practice and introduction of perceived professional and liability risks. The study concludes that digital health adoption is determined less by technological sophistication than by its integration into human systems. Scaling these innovations effectively requires prioritizing tools that align with existing workflows and developing a supportive policy ecosystem to address the professional concerns of frontline health workers.