Article Abstract

Article Abstract

Online ISSN: 1099-176X Print ISSN: 1091-4358
The Journal of Mental Health Policy and Economics
Volume 28, Issue 3, 2025. Pages: 77-96
Published Online: 1 September 2025

Changes in Access to Substance Use Disorder Treatment Associated with the 2008 U.S. Parity Law

Timothy B. Creedon,^1* Constance M. Horgan,² Xiaodong Liu,³ Dominic Hodgkin¹

¹PhD, The Heller School for Social Policy and Management, Brandeis University, Waltham, MA, USA.
²ScD, The Heller School for Social Policy and Management, Brandeis University, Waltham, MA, USA.
³EdD, Department of Psychology, Brandeis University, Waltham, MA, USA.

*Correspondence to: Timothy B. Creedon, PhD, The Heller School for Social Policy and Management, Brandeis University, Waltham, MA 02453, USA. E-mail: tim.creedon@gmail.com

Source of Funding: Supported by the National Institute on Drug Abuse (NIDA) F31 DA040402 and the National Institute on Alcohol Abuse and Alcoholism (NIAAA) T32 AA007567.

Abstract

This study examines whether the U.S. 2008 Mental Health Parity and Addiction Equity Act (MHPAEA) increased substance use disorder (SUD) treatment rates among adults with group-based private insurance. MHPAEA mandated that private health plans covering mental health and SUD benefits provide coverage no more restrictive than for general medical care. Using nationally representative survey data from 2006-2014 and difference-in-differences methods, we compare adults with group-based private insurance to multiple comparison groups. We find no statistically significant association between MHPAEA and increased SUD treatment rates. Despite potential improvements in financial protection, fewer than 10% of adults with SUD received treatment, while perceived unmet need remained below 4%. Non-financial barriers persisted as primary obstacles—particularly ambivalence about treatment and lack of coverage knowledge. Results suggest that while insurance parity is important for equitable access, additional interventions addressing coverage and treatment awareness and provider availability are necessary to meaningfully increase SUD treatment use.  

Background: Historically, U.S. health insurance plans included fewer and more restrictive benefits for mental health (MH) and substance use disorder (SUD) treatment compared to general medical care. The 2008 Mental Health Parity and Addiction Equity Act (MHPAEA) mandated that group-based private health plans covering MH/SUD treatment do so in a way no more restrictive than coverage for general medical care. Multiple rounds of rulemaking, including 2024 final rules most recently, have strengthened federal regulation of plans’ non-quantitative treatment limits (NQTLs).

Aims of the Study: To investigate how SUD treatment rates, perceived unmet needs, and barriers to treatment changed for adults with group-based private insurance following MHPAEA.

Methods: We conducted a secondary analysis of annual, cross-sectional data from the National Survey on Drug Use and Health (2006-2014) with a sample of adults aged 18-64 years meeting criteria for SUD treatment need. We used difference-in-differences models to estimate and compare outcomes between adults with group-based private insurance (GBPI) and multiple comparison groups including those with individual-based private insurance (IBPI) before (2006-2009) and after (2011-2014) MHPAEA implementation.

Results: Among 32,605 survey respondents with SUD (weighted N=16,108,465), 17,065 individuals had GBPI. For this group, adjusted rates of any past-year SUD treatment remained low, and we did not detect a statistically significant change following MHPAEA implementation (6.4% pre-parity vs. 7.0% post-parity; +0.5 percentage points, 95% CI: -1.1 to 2.2, p=0.514). Difference-in-differences analysis showed no significant difference in changes between those with GBPI and those with IBPI (+3.1 percentage points, 95% CI: -3.8 to 10.0, p=0.380). Self-identified unmet SUD treatment need also remained consistently low (3.9% pre-parity vs. 3.9% post-parity; +0.1 percentage points, 95% CI: -1.0 to 1.1, p=0.895). Among GBPI enrollees reporting unmet need, no significant changes were observed in barriers related to cost (14.9% post-MHPAEA), treatment accessibility (22.8%), ambivalence about seeking treatment (66.8%), or stigma (19.1%). Only half of GBPI enrollees knew their insurance covered SUD treatment, with nearly 40% reporting they didn’t know.

Discussion: These findings align with other studies of U.S. parity laws, which have found little to no impact on SUD treatment rates despite potential improvements in financial protection. Limitations include reliance on self-reported data, inability to identify specific insurance plans exempt from MHPAEA, and lack of state-level identifiers to account for pre-existing state parity laws.

Implications for Health Care Provision and Use: Providers and health systems may consider new strategies to identify SUD treatment needs and improve awareness of insurance coverage among patients, as nearly four in 10 individuals with group-based private insurance and SUD were unaware of their SUD coverage.

Implications for Health Policies: While recent MHPAEA final rules strengthened enforcement mechanisms and prohibit restrictive NQTLs, our findings suggest additional policies may be needed to improve access to SUD treatment, including efforts to increase awareness of treatment need and coverage, reduce stigma, and enhance treatment availability.

Implications for Further Research: Future research could examine how the 2024 MHPAEA final rules affect NQTLs and investigate the combined effects of MHPAEA with other health reforms on SUD treatment access and strategies to overcome persistent non-financial barriers to treatment.

Received 2 June 2025; accepted 31 July 2025