Using the theory of change (ToC) to co-design a primary mental healthcare system for older people with common mental disorders in Hong Kong

Population ageing and the limited mental healthcare human resources are widening the service gap between older people's mental healthcare needs and the system's capacity in Hong Kong.Scaling up services through integration into the primary care system remains the main strategy to address unmet needs.In this study, we co-developed a primary mental healthcare system for older people with common mental health disorders with 33 stakeholders, including representatives from the government, primary healthcare services, charities, professionals, service users, caregivers, and researchers.The study had three phases, including (1) rapid situational analysis and survey to synthesise key elements and challenges of the existing service, ( 2) three rounds of Theory of Change (ToC) workshops (online) with stakeholders, and (3) reach consensus and finalise the ToC map.A shared vision of No Wrong Door in Practice was established, operationalised as older adults experiencing improved mental health through integrated services from any entry point.The resulting ToC incorporated two interconnected pathways: (1) medical-social collaboration to provide integrated and person-centred care, and (2) community integration to empower older persons and carers to seek help and navigate the system confidently.Specific interventions, outcomes and outcome indicators were identified in the Hong Kong context for both pathways.