Assessing the Impact of Parity in the Large Group Employer-Sponsored Insurance Market: Final Report. ABSTRACT


Summary: The Paul Wellstone and Pete Domenici Mental Health Parity and Addiction Equity Act of 2008 (MHPAEA) ensures that large group health plans and health insurance issuers offer comparable benefits for mental health (MH) and substance use disorder (SUD) services and medical/surgical services. This legislation builds on prior federal legislation from 1996, which extended parity to SUD services and provided a broader array of benefits, such as financial limits (e.g., unequal cost sharing), quantitative treatment limits (e.g., visit and stay limits), and processes and techniques for managing care (often called non-quantitative treatment limits). This report details an empirical investigation of the effects of MHPAEA on the large group employer-sponsored insurance market. Analyses focus on the impact of MHPAEA on access, frequency of use, and spending on outpatient behavioral health (BH) services.

Major Findings: MHPAEA had significant and positive effects on any use and frequency of SUD outpatient services and frequency of MH outpatient services. Although MHPAEA had a positive impact on average spending by insurer and enrollee, average out-of-pocket amount paid per outpatient visit by the enrollee did not increase. Hence, increases in utilization of MH and SUD outpatient services drove increases in spending due to MHPAEA, and not increased cost sharing by the enrollee. Analyses of opioid use disorder (OUD) and non-OUD SUD services supported the conclusion that effects on utilization and spending were attributable to parity and not to general trends related to the OUD crisis. In most cases, the impacts of MHPAEA were similar in direction across MH and SUD outpatient services, but the magnitude of effect was greater for SUD services. Finally, findings showed that parity resulted in a dramatic shift toward out-of-network providers for SUD outpatient services.

Purpose: This study empirically assessed the impact of the MHPAEA on the private, large group employer-sponsored insurance market. We analyzed whether MHPAEA had population-level effects on the following outcome dimensions for outpatient services: any use, frequency of use, spending, and reimbursement.

Methods: We used data from the Truven Health MarketScan® Commercial Claims and Encounters Database from January 1, 2005, through September 30, 2015. The study population consisted of enrollees younger than 65 years with continuous enrollment in employer-sponsored insurance plans. We designated January 1, 2011, as the beginning of the post-parity period (to align with the passage of the interim final rule). An interrupted time series regression framework was used to estimate the impact of parity on each outcome, with population-level summarized monthly measures of outcomes. Analysis focused on outcomes for MH and SUD outpatient services, but we also examined OUD and non-OUD SUD services and outcomes for high utilizers and vulnerable subpopulations. In lieu of a control group, results were compared with non-BH services.