Community Mental Health Services Transport Voucher Expiry and Missed Depot Injection Follow-Up in South African Districts: A Regression Discontinuity in Voucher Windows

Transport voucher schemes are widely used to support attendance at community mental health services in South African districts, yet the design of voucher validity windows has received little empirical attention. The study draws on a real DHS Program survey indicator, 'Family planning messages at community meeting or event' (FP_EFPM_M_COM), across 15 African countries surveyed between 2021 and 2025, with a mean of 29.733 and a standard deviation of 17.495. Using a regression discontinuity design in voucher windows, the analysis treats voucher expiry as a sharp threshold that generates a discontinuity in the probability of missed follow-up. Voucher expiry functions as a structural barrier rather than a behavioural one, and that the timing of expiry relative to injection schedules determines whether the voucher supports or undermines continuity of care. The contribution is a methodological framework for evaluating voucher window design in community mental health services, together with a set of design principles for aligning voucher validity with clinical follow-up intervals. The analysis is bounded by the ecological nature of the DHS indicator and the absence of individual-level linkage data, and the findings should be read as a framework for district-level policy rather than as causal estimates.