The Impacts of 1115 Medicaid Substance Use Disorder Waivers on Medicaid‐Paid Use of Residential Treatment and Other Types of Services in 20 States

Objective To assess the association between the implementation of 1115 Medicaid substance use disorder (SUD) waivers and changes in Medicaid‐paid use of residential treatment and other types of services. Study Setting and Design We compared 20 states with SUD waivers to 14 non‐waiver states using a staggered difference‐in‐differences design. Primary outcomes were Medicaid‐paid opioid‐use disorder (OUD) related residential treatment stays and length of stay (LOS). Secondary outcomes included admissions and LOS for all‐cause and OUD‐related inpatient stays, psychiatric hospital admissions, emergency department (ED) visits, outpatient visits, and primary care visits. Data Source and Analytic Sample We used the 2016–2021 Transformed Medicaid Statistical Information System (T‐MSIS) Analytic Files (TAF). The analytic sample included Medicaid enrollees ages 18–64 with OUD. Principal Findings On average, waiver implementation was associated with an increase in residential treatment stays (estimate: 0.4%; 95% CI: 0.1%–0.7%), OUD‐related inpatient visits LOS (estimate: 0.3 days; 95% CI: 0.0%–0.5%), psychiatric hospital LOS (estimate: 1.0 days; 95% CI: 0.6 days–1.4 days), primary care visits (estimate: 3.0%; 95% CI: 1.2%–4.7%), and OUD‐related primary care visits (estimate: 2.7%; 95% CI: 0.9%–4.4%); and a decline in all‐cause inpatient visits (estimate: −0.9%; 95% CI: −1.9% to −0.0%) and OUD‐related inpatient visits (estimate: −0.8%; 95% CI: −1.6% to −0.0%). Results for psychiatric hospital LOS and OUD‐related primary care visits were sensitive to adjusting for pre‐trends. Among four early‐adopting states (Indiana, Louisiana, New Jersey, Virginia), Medicaid‐paid residential treatment increased 1–4 years following waiver implementation (e.g., 2‐year estimate: 2.8%, 95% CI: 2.5%–3.0%), and inpatient visits declined 1–4 years following waiver implementation (e.g., 2‐year estimate: −3.1%, 95% CI: −3.5% to −2.6%). Conclusions SUD waivers were associated with a small increase in Medicaid‐paid residential treatment and a decline in inpatient visits across states, with changes being concentrated among early‐adopting states.