It appears Americans are more anxious than ever. The number of Americans overdosing from anxiety drugs has quadrupled in the past couple of decades, according to a study in the American Journal of Public Health.

Now there's alarming news about fake anxiety drugs that are even more dangerous than the real ones.

A pill made to look like the popular anti-anxiety drug Xanax has been appearing from California to Florida, and it's cut with fentanyl, an extremely dangerous opioid. Fentanyl made headlines when it was revealed Prince may have died from consuming it.

Fentanyl is 50 times stronger than heroin, and it has caused many deaths around the country.

"Fentanyl is a synthetic opioid with 100 times the potency of morphine, with rapid central nervous system penetration, resulting in rapid central nervous system depression (making the user sleepy) and respiratory depression (stopping a user from breathing)," Annie Arens, a toxicology expert at the University of California, San Francisco, told ATTN: in an email. "This dangerous combination of rapid and severe symptoms makes this a potentially fatal drug in overdose."

The counterfeit Xanax looks very similar to the real one, so someone may not realize she's taken the fake one until it's too late. Taking the counterfeit drug just once can be deadly.

Even the people selling it may not realize it's a fake. High school and college students who use anxiety drugs to deal with school stress might fall victim to the fake version, and a student who simply wants to relax before an exam could end up dead in the process.

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"Young adults in particular are at high risk for nonmedical use of pharmaceuticals, with estimates that nearly 3 percent of people between the ages of 18 to 25 have engaged in the nonmedical use of pain relievers in the previous month," Arens said. "The nonmedical use of pharmaceuticals represents a serious and burgeoning public health risk. Of great concern is that people may be turning to street dealers to purchase these pharmaceuticals and be exposed to dangerous counterfeit products."

Counterfeit Xanax is among the most-reported fake drugs laced or cut with fentanyl, but counterfeit pharmaceuticals that look like the pain medications Percocet and Norco have also been found to include fentanyl, the National Institute on Drug Abuse warned.

This dangerous problem shows the importance of purchasing prescription drugs by legal means. If you really want to be safe, it might be a good idea to take a toke of marijuana instead of a prescription painkiller or anti-anxiety drug.