The Impact of the Affordable Care Act Insurance Expansions on Opioid-Related Emergency Department Visits

Amid rising opioid-related deaths and hospital use, the 2010 Patient Protection and Affordable Care Act (ACA) was signed into law, with the central coverage provisions implemented in 2014. We leverage these ACA coverage expansions (including Medicaid expansion and Marketplaces) to study the impact of health insurance on opioid-related emergency department (ED) visits while accounting for potentially confounding changes in relevant state-level policies. We use zip code–level ED utilization data from the 2010–18 Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SID) and State Emergency Department Databases (SEDD) for 29 states. In difference-in-difference-in-differences (DDD) models that compared low- and high-uninsurance areas within states, we found evidence of a dose-response relationship between pre-ACA uninsurance and changes in ED visit rates in both expansion and non-expansion states: areas with higher uninsurance rates prior to the ACA saw larger reductions in opioid-related ED visits after the ACA took effect. Effects were also time-varying, with no significant dose-response relationship emerging until the third year of ACA implementation. These estimates suggest that increasing insurance coverage among the uninsured may help mitigate harms of the opioid crisis.