Oregon Medicaid health experiment

The Oregon health insurance experiment (sometimes abbreviated OHIE) was a research study looking at the effects of the 2008 Medicaid expansion in the U.S. state of Oregon, which occurred based on lottery drawings from a waiting list and thus offered an opportunity to conduct a randomized experiment by comparing a control group of lottery losers to a treatment group of winners who were eligible to apply for enrollment in the Medicaid expansion program after previously being uninsured.

The study's results have been published in the academic journals The Quarterly Journal of Economics, Science, The New England Journal of Medicine, and the The American Economic Review. In the first year after the lottery, Medicaid coverage was associated with higher rates of health care use, a lower probability of having medical debts sent to a collection agency, and higher self-reported mental and physical health. In the eighteen months following the lottery, researchers found that Medicaid increased emergency department visits. Approximately two years after the lottery, researchers found that Medicaid had no statistically significant impact on physical health measures, though "it did increase use of health care services, raise rates of diabetes detection and management, lower rates of depression, and reduce financial strain."

Commentators in publications such as Forbes and RealClearPolitics cited the study as evidence that the Medicaid program doesn't fulfill its central cause of assisting the American poor, while other commentators in publications such as The New Republic and the Daily Kos stated that the evidence of improved financial security and mental health provided a significant social benefit.

In 2008, Oregon began an expansion of its Medicaid program for low-income adults. Because officials could not afford coverage for all those who wanted to enroll, they decided on the novel approach of allocating the limited number of available slots by lottery. Thus, a situation allowing for a randomized experiment occurred, with a control group of individuals not selected by the lottery and a treatment group of individuals selected by the lottery and thus eligible to apply for Medicaid.

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