Deaths from overdoses of prescription sedatives known as benzodiazepines—including Xanax and Valium—are on the rise, according to a report in the New England Journal of Medicine. According to data from the National Institute on Drug Abuse, overdose deaths involving benzodiazepines increased from 1,135 in 1999, to 8,791 in 2015.

Benzodiazepines are prescribed to treat conditions including anxiety, insomnia and seizures. Overdoses have increased in the past decade, as the number of prescriptions for these drugs has increased, HealthDay reports. Prescriptions for benzodiazepines rose by 67 percent between 1996 and 2013, from 8.1 million to 13.5 million.

“These are highly addictive and potentially lethal drugs, and many people don’t know that,” lead author Dr. Anna Lembke of the Stanford University School of Medicine said. “Sadly, most physicians are also unaware of this and blithely prescribe them without educating their patients about the risk of addiction.”