Strengthening South Africa's health system through integrating treatment for mental illness into chronic disease care (Project MIND) Integrating mental health care into primary health care services could reduce the impact of both chronic communicable and non-communicable diseases (NCDs). Like many low- and middle-income countries (LMICs), South Africa (SA) faces the challenge of how to reduce the high prevalence and impact of communicable diseases and NCDs, including mental disorders where limited services are available. Mental disorders are important to address among patients with chronic diseases as these problems are associated with poor adherence to treatment, more rapid disease progression and treatment failure. As treatment failure increases the use of health services and health service costs, chronic disease care in LMICs must be expanded to include mental health care. The integrated delivery of mental health services and chronic disease care has been shown to not only improve access to mental health care but also the mental health of patients living with a chronic disease. .   Yet, limited knowledge of how mental health care can be integrated into chronic disease services in ways that are acceptable to patients and providers and feasible to implement with few resources has delayed the integration of services in SA. The provision of integrated mental health and chronic disease services has also been delayed by questions about whether services should be vertically or horizontally integrated. Vertically integrated services are delivered at the same location, but mental health and chronic disease services are provided by separate cadres of health workers. Horizontally integrated services are delivered at the same location by the same staff are responsible for mental health and chronic disease care. The goal of this project is to answer these questions by assessing current capacity and barriers to integrating mental health services into chronic disease care and by comparing the effectiveness and cost-effectiveness of a vertically and horizontally integrated model of service integration among patients receiving treatment for HIV or diabetes and who are at risk for treatment failure in Cape Town, SA. Through this project we hope to identify a feasible, acceptable and effective model for integrating mental health services into chronic disease care that is applicable to other LMICs. Findings from this study are likely to be highly relevant for use in other LMICs given similarities between the burden of disease, treatment populations, and treatment systems in SA and other LMICs.  The study will comprise two phases. In the first phase, we will conduct in-depth interviews with a range of healthcare providers in HIV and diabetes services to assess barriers to integration and the feasibility and acceptability of our proposed models of service integration (Aim 1). Findings from this phase will be used to adapt our evidence-based mental health service package for optimal integration into chronic disease services. In phase two, a clustered randomised controlled trial will be conducted. We will select 24 HIV and 24 diabetes clinics to randomise to a vertically integrated arm, horizontally integrated arm, or treatment as usual (no integration). We will recruit 25 patients at risk for treatment failure from each of these clinics (total 1200 patients). After study enrollment, a baseline assessment will be completed by a fieldworker. Participants recruited from clinics randomised to either the vertically integrated or horizontally integrated arm will then receive their intervention sessions. All participants, irrespective of their intervention arm, will be tracked for 6- and 12-month follow-up interviews.  At these interviews, fieldworkers blinded to their intervention arm will re-administer the baseline assessment and biological specimens will be collected to assess for chronic disease outcomes. Findings from this phase will be used to evaluate the relative effectiveness and cost-effectiveness of our proposed models of service integration (Aims 2-3). The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.