More than 11,000 people in the United States were treated for bike injuries related to substance use between 2019 and 2020, according to a new study. Researchers said it was already known that people injured in bike crashes related to substance use tend to have more serious injuries.

They reviewed data from the National Electronic Injury Surveillance System, a hospital-based database. They found that in the U.S., methamphetamine and marijuana are the two most common substances associated with bike crash patients seen in the emergency room. Reported injuries included fractures and internal organ injuries. Nearly one-third of patients had to be admitted to the hospital, HealthDay reports. Young adults ages 25 to 44 represented the largest proportion of patients.

“When these patients present to the emergency department, it becomes important not only to treat the injuries but also to refer patients to drug treatment in an effort to intervene and prevent further negative events related to drug use,” study lead author Bart Hammig, Ph.D., M.P.H., of the Public Health Program at the University of Arkansas, said in a news release.