IMPORTANCEThe transition from prison to community is characterized by elevated morbidity and mortality, particularly owing to drug overdose. However, most formerly incarcerated adults with substance use disorders do not use any health care, including treatment for substance use disorders, during the initial months after incarceration. OBJECTIVE To evaluate whether a prerelease Medicaid enrollment assistance program is associated with increased health care use within 30 days after release from prison. DESIGN, SETTING, AND PARTICIPANTSThis retrospective cohort study included 16 307 adults aged 19 to 64 years with a history of substance use who were released from state prison between

Objective: To estimate the incremental associations between the implementation of expanded Medicaid eligibility and prerelease Medicaid enrollment assistance on Medicaid enrollment for recently incarcerated adults. Data Sources/Study Setting: Data include person-level merged, longitudinal data from the Wisconsin Department of Corrections and the Wisconsin Medicaid program from 2013 to 2015. Study Design: We use an interrupted time series design to estimate the association between each of two natural experiments and Medicaid enrollment for recently incarcerated adults. First, in April 2014 the Wisconsin Medicaid program expanded eligibility to include all adults with income at or below 100% of the federal poverty level. Second, in January 2015, the Wisconsin Department of Corrections implemented prerelease Medicaid enrollment assistance at all state correctional facilities. Data Collection/Extraction Methods: We collected Medicaid enrollment, and state prison administrative and risk assessment data for all nonelderly adults incarcerated by the state who were released between January 2013 and December 2015. The full sample includes 24 235 individuals. Adults with a history of substance use comprise our secondary sample. This sample includes 12 877 individuals. The primary study outcome is Medicaid enrollment within the month of release.

Research Objective Substance use disorders (SUDs) are endemic and undertreated among the 1.2 million individuals incarcerated in state prisons. Reentry to the community is characterized by elevated rates of morbidity and mortality, particularly due to drug overdose. Treatment of SUDs before and during the reentry period reduces the risk of relapse and overdose. However, most formerly incarcerated adults with SUD do not receive any treatment in the initial weeks and months post‐release. We estimate the impact of Medicaid enrollment on the likelihood of receiving any health care, and SUD‐related care specifically, in the 30‐days post‐incarceration for adults with a history of substance use. Study Design We study a natural experiment in which the Wisconsin Department of Corrections introduced prerelease Medicaid enrollment assistance. All adults with income below 100% of the federal poverty level were eligible for Medicaid throughout the study period. Using person‐level longitudinal data that links Corrections and Medicaid data, we implemented two‐stage least squares (2SLS) instrumental variables (IV) analysis. Two variables comprised the instruments corresponding to two policy periods: a 3‐month enrollment assistance implementation period and the fully operational enrollment assistance program. The key assumption is that timing of release is unrelated to the outcomes, conditional on the other variables in the model. Outcomes included care received within 30‐days of release: any outpatient visit (all‐cause, SUD, and opioid use disorder [OUD]), medication for OUD (MOUD), emergency department and inpatient events (all‐cause and drug overdose). Population Studied The population includes 18,187 adults ages 18–64 incarcerated by the state, with a history of substance use, who were released between April 2014 – December 2016. Principal Findings The instruments were correlated with Medicaid enrollment in the month of release (F‐statistic of 455). The likelihood of Medicaid coverage in the month of release increased from 39% at baseline, to 56% after introduction of the enrollment assistance program to 69% after it was fully operational. At baseline, the percentage of adults with health care use within 30‐days of release was 16% for any outpatient visit, 2.5% for an SUD‐related visit, 0.7% for an OUD‐related visit, 0.3% for MOUD, 5.5% for any ED visit, and 0.8% for an inpatient visit. Acquiring Medicaid coverage increased the likelihood of outpatient health care use within 30‐days of release (p < 0.05) by 26 percentage points (pp) for any outpatient visit, 2.6 pp for OUD‐related outpatient visit, 3.6 pp for an SUD‐related outpatient visit, and 1.5 pp for MOUD. Medicaid coverage was not associated with a change in emergency or inpatient care. Conclusions Medicaid coverage among adults releasing from prison increased immediate access to outpatient care overall and for SUDs specifically for adults with a history of substance use. However, it did not reduce the likelihood of emergency or inpatient care. These findings highlight...