Exploring contextual barriers and facilitators to sustaining mental health integration in primary care: a mixed-methods analysis of adaptive mechanisms and multi-level dynamics in Lagos, Nigeria

Adaptive mechanisms represent legitimate and necessary sustainability strategies in resource-constrained settings, not implementation failures. We propose 'functional fidelity' (maintaining core outcomes through flexible processes) and 'adaptive capacity' as crucial theoretical extensions for implementation science in LMICs. Sustainable mental health integration requires frameworks that recognise and support frontline innovation while ensuring quality safeguards are maintained, offering a more realistic pathway to closing the global mental health treatment gap.