Most overdose deaths from cocaine or psychostimulants such as methamphetamine also involve opioids, according to a new report from the Centers for Disease Control and Prevention (CDC).

Opioids were present in 79% of overdose deaths involving cocaine and about 66% of those involving psychostimulants in 2021, the CDC found. The rate of overdose deaths involving both cocaine and opioids in 2021 was 7.4 times the rate in 2011, CNN reports.

Dr. Nora Volkow, director of the National Institute on Drug Abuse, who was not involved in the study, said the new research highlights the dangers of fentanyl. “Cocaine combined with fentanyl is much more toxic and lethal,” she said. “Methamphetamine can kill more than cocaine by itself, but having said that, it’s much more dangerous when you combine it with fentanyl. This accounts for why we’re seeing firsthand a high rise in mortality from these two drugs.”