Oregon Medicaid Lottery

Summary

Oregon's random Medicaid lottery created a rare natural experiment in a domain where RCTs are normally impossible. Gaining coverage dramatically increased health care use and eliminated catastrophic medical bills, and significantly improved mental health. However, the two-year follow-up found no statistically significant improvements in blood sugar, blood pressure, or cholesterol. This null result was widely cited by ACA critics. Defenders noted that two years is too short to detect improvements in chronic disease outcomes, and that financial protection and mental health are independently valuable. The study is a masterclass in how the same data can be interpreted in opposing directions.

Research question

"What is the causal effect of gaining Medicaid coverage on health care use, financial security, and health outcomes?"

Methodology

Result

Mixed

ER use: +40%; doctor visits: +35%; financial hardship: −25% (catastrophic medical bills); depression: −30%; blood sugar, blood pressure, cholesterol: no significant improvements at 2 years

Evidence strength

Moderate

Randomized trial; replication status unknown or limited.

Replication status

N/A