More people with substance use disorders and mental illness had insurance coverage in 2014 because of the expansion of health insurance under the Affordable Care Act (ACA), a new study finds. Many barriers to treatment remain, according to researchers at the Johns Hopkins Bloomberg School of Public Health.

The study found there were no significant increases in use of services to treat substance use disorders or mental illness, HealthDay reports.

“We got more people covered, but we didn’t make dramatic progress in closing the under-treatment gap,” lead researcher Brendan Saloner said in a news release. “We need to find ways to take the next step and ensure people are seeing the providers who can help them.”

The study included data from almost 30,000 adults with mental illness and more than 19,000 with substance use disorders. The researchers compared insurance coverage for two periods: 2011-2013, before the ACA was implemented, and 2014, the first year it was in place.