Highlighted Project: Oregon Health Insurance Experiment

Medicaid coverage reduces depression and financial strain, increases utilization

The Oregon Health Insurance Experiment (OHIE) showed that acquiring Medicaid coverage profoundly impacted mental health, reduced financial strain and decreased medical debt. However, it did not significantly impact key clinical health markers. The research also showed that uninsured people who received Medicaid coverage saw an increase in all types of health care utilization; this increase was maintained throughout the first few years of coverage.

In the first one to two years of coverage:

  • Medicaid increased the use of health care services including hospitalizations, emergency department visits, outpatient visits, prescription drug use and preventive care use.
  • Medicaid improved access to medical care services and reduced unmet need.
  • Medicaid decreased financial strain. It reduced medical debts sent to collection agencies, lowered the likelihood of borrowing money or skipping other bills to cover medical expenses, and virtually eliminated catastrophic out-of-pocket medical expenditures.
  • Medicaid improved self-reported health and reduced rates of depression, but had no statistically significant effect on clinically measured health outcomes. Clinical measures included screenings of blood pressure, cholesterol and glycated hemoglobin.

OHIE was the first study to evaluate the impact of having or not having insurance coverage within a randomized controlled trial, the gold standard in medical and scientific studies. The study was conducted by researchers from Center for Outcomes Research and Education (CORE), Harvard School of Public Health, Massachusetts Institute of Technology and the National Bureau of Economic Research (NBER).

How this study was made possible

This unique study was fielded in cooperation with the State of Oregon. In 2008, Oregon held a lottery to accept additional low-income, uninsured residents into its Medicaid program. About 90,000 applied for 10,000 available openings, and application opportunities were assigned by chance.

Data collection began in 2008 and included surveys, in-person interviews, in-person biomarker data collection, administrative data analysis and intensive qualitative interviews. Researchers compared outcomes between people randomly selected by the lottery and those not selected in order to determine the impact of Medicaid. The study measured the impact of health insurance on self-reported physical and mental health, financial strain, health care utilization, and objective clinical health outcomes. 

Related Publications

  • Allen H, Baicker K, Finkelstein A et al. What the Oregon health study can tell us about expanding MedicaidHealth Affairs. 2010; 29(8): 1498-1506.
  • Finkelstein A, Taubman S, Wright B et. al. The Oregon health insurance experiment: evidence from the first year. The Quarterly Journal of Economics. 2012; 127 (3): 1057-1106.
  • Taubman S, Allen H, Wright B, Baicker K, Finkelstein A. Medicaid increases emergency department use: evidence from Oregon’s health insurance experiment. Science. 2014, Jan. 17; 343(6168):263-268.
  • Baicker K, Taubman S, Allen H, Bernstein M, Wright B, Finkelstein A. The Oregon experiment ‐ effects of Medicaid on clinical outcomes. New England Journal of Medicine. 2013 May 2; 368: 1713-1722.
  • Wright B, Conlin A, Allen H, Tsui J, Carlson M, Li, HF. What does Medicaid expansion mean for cancer screening & prevention? Results from a randomized trial on the impacts of acquiring Medicaid coverage. Cancer. 2016 Mar 1; 122(5):791-797.

Beyond OHIE: pairing coverage expansion with delivery system reform 

OHIE demonstrated that while health care coverage could drive improvements in some outcomes, coverage alone could not improve health, improve care and reduce costs. In 2012, Oregon took the next step by launching a broad health reform movement called the Coordinated Care Model, aimed at pairing coverage expansion with delivery system reform. The reform included the establishment of Coordinated Care Organizations (CCOs), which are regional entities charged with integrating physical, mental and dental health care. CCOs are held accountable for achieving a set of quality metrics while delivering care under a fixed global budget.

The Oregon Health Authority tracks 32 health and quality metrics for members of CCOs. The agency contracts with CORE to produce monthly dashboards that give CCOs a snapshot of their performance.

CORE also has conducted research and program evaluation on the effectiveness of CCO strategies. Learn more ›