This brief by the Kaiser Family Foundation publication outlines the recession’s effect on Medicaid enrollment, finding that it was the primary cause of the increased Medicaid spending.

From the report:

Millions of Americans lost jobs and income during the recent recession, leading many to turn to the Medicaid program for health coverage. From December 2007 through December 2009, Medicaid monthly enrollment rose by nearly 6 million (14 percent) largely due to the deepening recession and supported by the American Recovery and Reinvestment Act’s (ARRA) enhanced federal funding and protections against eligibility restrictions. Without Medicaid, the number of uninsured Americans would have undoubtedly been higher than the 50 million uninsured in 2009.

Full Report: Medicaid Spending Growth and the Great Recession, 2007-2009 (A Fact Sheet)  

Kaiser Family Foundation. (2011). Medicaid Spending Growth and the Great Recession, 2007-2009.