"The reasons for the more pronounced psychoactive effects and severe and fatal poisoning seen with synthetic cannabinoids are not particularly well understood, but at least two factors are likely to be important: the high potency of the substances and the unintentionally high doses that users are exposed to.
"Synthetic cannabinoids, also known as synthetic cannabinoid receptor agonists, are a group of drugs that mimic the effects of a substance found in cannabis called tetrahydrocannabinol (THC). THC is responsible for many of the psychoactive effects of cannabis which give that feeling of being ‘stoned’ or ‘high’ (Gaoni and Mechoulam, 1964; Huestis et al., 2001; Pertwee, 2005a; Pertwee, 2014). These effects are caused by activating a receptor in the brain called the cannabinoid receptor type 1 (CB1 receptor) (Huestis et al., 2001; Pertwee, 2014).
"MTF first addressed the use of synthetic marijuana in its 2011 survey, by asking 12th graders about their use in the prior 12 months (which would have covered a considerable period of time prior to the drugs being scheduled). Annual prevalence was found to be 11.4%, making synthetic marijuana the second most widely used class of illicit drug after marijuana among 12th graders.
"Spice" and Synthetic Cannabinoids: "Despite its [marijuana's] long history of use and abuse for both medical and recreational purposes, a new generation of synthetic cannabinoids has recently emerged on the market, which are sold on the Internet as herbal mixtures under the brand names of 'Spice,' 'Spice Gold,' 'Spice Diamond,' 'Arctic Spice,' 'Silver,' 'Aroma,' 'K2,' 'Genie,' 'Scene' or 'Dream,' and advertised as incense products, meditation potpourris, bath additives, or air fresheners.