More Americans than ever are taking anxiety drugs, such as Valium and Xanax, to help manage their mental health. But new findings published in the American Journal of Public Health show that popping these prescription pills is also a risk business because the number of people overdosing on them has quadrupled over the past 20 years, NBC News reports. 

For the study, a team of scientists at Albert Einstein College of Medicine in New York reviewed a number of large health surveys conducted between 1996 and 2013. Scientists specifically looked for trends each year in the use and abuse of benzodiaxepine drugs, a.k.a. ’benzos,’ prescribed to treat conditions such as anxiety, mood disorders and insomnia. 

Researchers found that, today, more than 5 percent of American adults, or 13.5 million people, fill a prescription for these highly addictive drugs, an increase of nearly 67 percent in this country since 1996. In addition, scientists found a similarly large increase in teh number of pills each adult was prescribed. 

What’s more, findings showed benzodiazepines accounted for nearly a third of the 23,000 people who died from prescription drug overdoses in 2013. 

“Overdoses from benzodiazepines have increased at a much faster rate than prescriptions for the drugs, indicating that people have been taking them in a riskier way over time,” said Marcus Bachhuber, MD, of the Albert Einstein College of Medicine, one leader of the study. 

Researchers said it was unclear why overdoses soared, but said it could be because people are taking the drugs for longer periods of time, rasing the odds of an overdose. In addition, scientists believe the pills could be making their way to people who don’t have prescriptions. 

Last year, more than 47,000 Americans died from drug overdoses that involved narcotics such as heroin and opioid painkillers. For more information about the prescription painkiller epidemic in the United States, click here.