Community Mental Health Services Screening Uptake and Cardiovascular Risk Detection in South African Primary Care: A Regression Discontinuity in Age Eligibility

South African primary care offers an unusual natural experiment in age-based eligibility for community mental health screening: users below a defined age threshold are routed to routine services, while those at or above it become eligible for structured cardiovascular risk assessment within the same mental health encounter. The analysis draws on the DHS Program indicator 'Percentage receiving injection given by health care provider' (FP_SPUS_W_SPH) for 14 African countries surveyed between 2021 and 2025, with a mean of 91.964 and a standard deviation of 12.468 across the 14 country-survey observations. The contribution is a design specification and a set of falsification tests, not an estimated effect: the paper argues that age-eligibility discontinuities in South African primary care are a credible but fragile identification strategy, and that their credibility depends on three conditions that current routine data systems do not yet satisfy. The paper concludes that the design is worth fielding only where age recording is exact, where the threshold is enforced by an information system rather than by clinician discretion, and where cardiovascular risk detection is measured independently of the mental health screening decision.