Proponents of the Affordable Care Act (ACA) argued—and continue to argue—that it will reduce frequent use of the emergency department (ED) by the same people with expanded coverage, especially for those most likely to make repeated visits to the ED.

Now, four years after several major expansion provisions of the ACA kicked in, researchers examined data from California to see just what impact the healthcare legislation had on ED usage.

The study—led by Shannon McConville, a senior research associate at the Public Policy Institute of California in San Francisco—was published online June 4 in Health Affairs.

“The likelihood of being a frequent ED user decreased in the two years following implementation of the major coverage provisions of the ACA,” the authors wrote. “Still, with the sizable increase in ED patients covered by state Medicaid programs and higher baseline odds of frequent ED use among Medicaid patients relative to those with other coverage, there has been an overall increase in both the share and the absolute number of ED patients who are frequent users.”