Medicaid Mental Health and Substance Use: Expansion Trends and the Fiscal Pressure Ahead Authors: Heather Saunders and Elizabeth Hinton Published: May 13, 2026

https://www.kff.org/medicaid/medicaid-mental-health-and-substance-use-expansion-trends-and-the-fiscal-pressure-ahead/ Medicaid is a major source of financing for mental health and substance use disorder care. It covers nearly one-third of all adults with mental illness and nearly one-quarter of adults with substance use disorders (SUD), including many people with more intensive behavioral health needs. This includes adults with serious mental illness (SMI) and nearly half of all adults with opioid use disorder (OUD). Because Medicaid covers a large share of people with behavioral health conditions and finances a substantial share of treatment services and medications, it plays a central role in access to behavioral health care.