The Paul Wellstone and Pete Domenici Mental Health Parity and Addiction Equity Act (2008), expanded by the ACA, requires insurance plans to cover mental-health and substance-use disorder treatment on terms no more restrictive than physical health.
Enforcement remains a problem. Studies find systematic disparities: out-of-network use rates 5-10x higher for mental health, narrower provider networks, more frequent prior-authorization, and lower reimbursement rates. The 2024 final rule strengthens analysis and reporting requirements.
Provider supply is also a constraint: most U.S. counties have severe shortages of psychiatrists and substance-use specialists.