For several hours on July 12, 2016, a group of 33 people in New York City were in a "zombie-like" state: staring blankly, moving and responding to medics slowly, and occasionally groaning. This bizarre spectacle was the result of a very bad trip on a synthetic cannabinoid that Reddit users have called "out-of-this-world potent."

Synthetic cannabinoids are used by researchers to study the nervous system, but they are now produced illegally and sold on the street. Though smoked like cannabis, synthetic cannabinoids share little in common with it or its active ingredient, THC. Indeed, the synthetic drugs are much more dangerous because some have killed people. 

To determine the cause of the NYC case, researchers chemically analyzed the contents of the packaging (shown in the...