A new study finds people with substance use disorders (SUDs) are more susceptible to COVID-19 and its complications.

The researchers analyzed electronic health records of millions of U.S. patients. They found that although people with an SUD constituted 10.3% of the total study population, they represented 15.6% of the COVID-19 cases. Those with a recent SUD diagnosis were more likely than those without one to develop COVID-19. This effect was strongest for opioid use disorder, followed by tobacco use disorder. People with an SUD diagnosis were also more likely to be hospitalized or die from COVID-19 than people without an SUD.

“The lungs and cardiovascular system are often compromised in people with SUD, which may partially explain their heightened susceptibility to COVID-19,” study co-author Dr. Nora Volkow, Director of the National Institute on Drug Abuse, said in a news release. “Another contributing factor is the marginalization of people with addiction, which makes it harder for them to access health care services. It is incumbent upon clinicians to meet the unique challenges of caring for this vulnerable population, just as they would any other high-risk group.”