PROJECT SUMMARY/ABSTRACT While the opioid epidemic affects all levels of society, there are evident disparities in opioid use disorder (OUD), as well as access to treatment for OUD, including medications for opioid use disorder (MOUDs). Adults involved with the criminal justice system are disproportionately affected by OUD and are more likely to go untreated for OUD. Insurance coverage is important for access to healthcare, including OUD treatment. Under the Affordable Care Act (ACA), some states expanded access to Medicaid to cover more low-income individuals, including childless adults. The majority of incarcerated individuals are low-income and uninsured and are, therefore, likely to be Medicaid eligible. Additionally, access to Medicaid for some criminal justice involved individuals is regulated by a federal law, commonly referred to as “inmate exclusion,” which prohibits Medicaid from covering health services for those in a jail, prison, detention center, or other penal facility. Some states terminate Medicaid for incarcerated individuals, while others suspend Medicaid coverage, which does not require re-enrollment upon release. While research has shown that ACA Medicaid expansion is associated with increased access to and utilization of MOUD in the overall population, little is known about the effects on criminal justice involved individuals. Moreover, little is known about the effects of state Medicaid suspension policies on OUD treatment outcomes in this population. To address this gap, my dissertation will use a difference-in-difference framework to estimate the effect of Medicaid expansion and Medicaid suspension policies on outcomes of interest using the Treatment Episode Datasets from 2000-2017. My aims are two-fold: 1) to describe OUD treatment outcomes for individuals referred to treatment by the criminal justice system over time, by geography, and by Medicaid policy status; and 2) to estimate the effects of Medicaid expansion and Medicaid suspension policies on treatment outcomes for criminal-justice referred admissions including: a) the proportion of criminal justice referred admissions with OUD with Medicaid coverage, private insurance coverage, and no insurance; b) the proportion of criminal justice referred admissions with OUD receiving MOUD overall and by insurance status; and 3) the proportion of criminal justice referred admissions with OUD completing treatment overall and by insurance status and MOUD utilization status. For each of these outcomes of interest, I will also explore these relationships by subgroups to capture OUD severity (i.e., primary substance, polysubstance use, intravenous drug use). Given the disproportionate OUD disease burden and lack of access to care for criminal justice involved individuals, it is critical to understand what types of policy interventions may be effective in addressing these disparities. This research will provide important and timely information to support evidence-based policy- and ...