More Americans with opioid use disorder are receiving treatment, but racial disparities persist, according to a new study.

Researchers at the University of Pittsburgh found rates of opioid addiction among Medicaid patients in 11 states increased from 3.3% in 2014 to 5% in 2018, HealthDay reports. The prevalence of medication treatment for opioid addiction increased from 47.8% to 57.1% during that period.

The study found that Black patients were much less likely than white patients to be treated with medication for their opioid addiction. They were also less likely to have continuity of treatment.

“This demonstrates that state Medicaid expansion provided access to care for a population that needed to be engaged in the health care system,” lead researcher Julie Donohue said in a news release. “Opioid use disorder can be treated, just like any other disease, but treatment is most successful when the patient has regular, unimpeded access to trained clinicians who can not only treat the disorder, but also oversee the rest of their health care.”