Determinants, Pathways, and Outcomes of Health Literacy in India: A System Dynamics Modelling Study.

Health literacy is a critical determinant of health. While many studies identify linear associations, the dynamic feedback mechanisms that create policy resistance and perpetuate health inequities remain poorly understood and studied. This study aims to develop a conceptual model of health literacy contextual for India, grounded in a systematic review of the literature, to identify key feedback loops and to test the comparative effectiveness of different policy interventions via system dynamics modelling. We conducted a systematic review to identify determinants, pathways and outcomes of health literacy in India. The search yielded 559 records. Two independent reviewers did title and abstract screening, resulting in 39 articles selected for full-text review. After four records could not be retrieved, 35 full texts were assessed for inclusion in the study, and 30 studies met the final inclusion criteria. Data extraction was done, and a Causal Loop Diagram (CLD) was developed iteratively. This conceptual model was then quantified into a Stock-and-Flow (S&F) simulation model using Python. We conducted a sensitivity analysis and simulated five distinct policy scenarios over 30 years. The model's behaviour is dominated by two reinforcing vicious feedback loops: 1) the 'Health Disparity Trap' (R1), where low socioeconomic status drives low health literacy and poor health, which in turn reinforces poverty; and 2) the 'System Trust Spiral' (R2), where poor health outcomes erode public trust, leading to care avoidance of care and further health decline of health. After running the simulation, the total population with poor health outcomes was 55.6 million, with 95% CI 43.8M-65.5M in the baseline scenario. Isolated interventions failed to show a significant improvement in the total population with poor health outcomes from the baseline. A Stacked Intervention, which was multimodal, produced the strongest effect, reducing the mean population with poor health outcomes to 35.7 million (95% CI: 24.9M-47.6 M). Health literacy is a complex and adaptive construct influenced by reinforcing mechanisms that make it resistant to single-point interventions. Policy must move from isolated projects to a multi-pronged, systemic strategy to produce significant impact.