People who combine meth and opioids are at greater risk of having a nonfatal overdose compared with those who use either substance alone, according to a new study of overdoses in rural U.S. communities.

Researchers from the Oregon Health & Science University found 22% of people in rural communities who used both meth and opioids had a nonfatal overdose in the previous six months, compared with 14% who used opioids alone and 6% who used meth alone. Those using both substances reported the least access to treatment, and only 17% of those using meth had naloxone.

The study included 3,048 people participating in the National Rural Opioid Initiative from 10 states who reported any past 30-day injection drug use or non-injection opioid use to get high, HealthDay reports.

“Co-use of methamphetamine and opioids is associated with a big increased risk of overdose in rural communities,” study author Dr. Todd Korthuis said in a news release. “Some people view rural areas as immune to problems like drug use and overdose, but they’re not.”