Fifty years of empirical research on medical assistance in dying: A mapping review.

BACKGROUND: Medical assistance in dying (MAiD) is authorized in an expanding number of jurisdictions, yet as it becomes embedded in routine care, the evidence base remains fragmented and poorly characterized. Across jurisdictions, fundamental questions remain about whether access is equitable, whether safeguards function as intended, and whether the evidence base can support policy evaluation. OBJECTIVE: To characterize the empirical MAiD evidence base by describing its scope and examining how study designs, populations, and research questions intersect. METHODS: We conducted a mapping review, searching five databases for empirical studies of MAiD published between 1975 and 2025. RESULTS: Of 1471 included studies spanning 65 countries, research output accelerated after 2018 but remained geographically and methodologically concentrated. Although quantitative designs dominated the first four decades, qualitative approaches are now modal (39% of recent studies). Study designs did not shift: observational (98.5%) and cross-sectional (78.5%) approaches predominated; longitudinal (1.8%), experimental (1.0%), and quasi-experimental designs (0.5%) were rare. Healthcare professionals constituted 62.1% of study populations while only 8.7% examined patients requesting or receiving MAiD. People denied MAiD, families and caregivers, and structurally marginalized groups were largely unstudied. Studies focused on stakeholder attitudes (46.4%) and public opinion (16.1%) with less attention to access, complex cases, and economic considerations. CONCLUSIONS: The field's research questions have diversified, but its methods and study populations have not. The resulting evidence base is poorly suited to assess patient access, safeguard performance, or cross-jurisdictional comparability, as these priority areas require standardized outcome reporting and linkage to administrative health system data.