Evaluating the Impact of the Mental Health Parity and Addiction Equity Act on Expanding Access for Adults with Behavioral Health Conditions: A Scoping Review

Background The Mental Health Parity and Addiction Equity Act (MHPAEA) was enacted to improve access to behavioral health care by ensuring that financial requirements and treatment limits are no more restrictive than those applied to medical-surgical services. Implementation through the Affordable Care Act (ACA) extended these protections to additional insurance markets, further strengthening opportunities for expanded access. Although MHPAEA and the ACA improved benefit design, concerns remain regarding nonquantitative treatment limits, provider shortages, and persistent inequities. A comprehensive assessment is needed to understand how these policies have influenced access, affordability, and equity for adults with behavioral health conditions. Methods This scoping review followed PRISMA-ScR guidelines and applied the population, concept, and context framework. Eligible studies included U.S.-based research examining adults aged 18 or older and evaluating the implementation or impact of MHPAEA and ACA-related parity provisions. Searches were conducted in PubMed, PsycINFO, Scopus, Web of Science, and federal grey literature from 1997 to 2025. Studies addressing treatment limits, benefit design, service utilization, financial protection, network adequacy, or equity outcomes were included. Data were charted and synthesized narratively. Results Findings indicate that MHPAEA, reinforced by ACA implementation, strengthened the structural foundation for expanded access through the elimination of quantitative treatment limits and improvements in outpatient mental health service use. However, restrictive nonquantitative treatment limits, narrow networks, and workforce shortages continued to limit meaningful access. Persistent disparities across socioeconomic, racial, and geographic groups further constrained the law’s impact. Conclusions MHPAEA improved the structural conditions necessary for expanded access, yet real-world access remains uneven. Stronger enforcement, greater transparency, workforce investment, and updated regulatory evaluation are needed to achieve equitable behavioral health access.