According to Think Progress:

[su_quote]Synthetic cannabinoids were born from pot prohibition. Clemson University organic chemist John W. Huffman created hundreds of synthetic cannabinoids starting in the 1980s because researchers had such a hard time getting actual marijuana for research. Though President Obama recently expressed support for reclassifying it, marijuana is still a Schedule I drug, meaning it’s very difficult for researchers to study legally. These compounds were similar enough to use in studies, and researchers could actually obtain them. “I always had a hunch that someday somebody would say: ‘Hey, let’s try smoking them.’,” Huffman has said since. “And lo and behold, that’s what happened.”

Today, synthetic pot appeals to people who cannot use marijuana for various reasons surrounding its illegality: They are regularly drug tested, they want to avoid arrest, they find synthetics to be more affordable, or they simply can’t find an illegal dealer.[/su_quote]

International Business Times adds:

[su_quote]Use of a synthetic drug that can cause extreme anxiety, delusions and violent behavior is on the rise in several U.S. states, sending more people to hospitals than ever before. On Thursday, U.S. health officials saw 172 reports of overdoses from spice, the street name for a class of drugs that contain a compound similar to THC, the high-inducing ingredient in marijuana.

That number represented the most single-day overdoses from the drug this year. Nationwide, there have been about 1,000 reports of spice-related hospitalizations in April alone, more than double the total number of cases seen in the first three months of 2015 and nearly four times the total recorded by this time last year, the New York Times reported.[/su_quote]