Studies have shown that Medicaid expansion has been associated with greater access to care, more preventive care, and improved chronic disease management.1 Medicaid expansion has also improved financial well-being among low-income families.2 While these are important findings, they are process measures that precede any potential changes in health. The critical question posed by many policy makers is whether Medicaid expansion improves health. Five years after implementation of the expansion an evidence base has begun to emerge.