How harmful is the synthetic drug spice: "potpurri"?

Can be very harmful: "spice" is not a single chemical; it is a term used to refer to several synthetic cannabinoids, or drugs that affect the same receptors as marijuana, and that are marketed under many names. However, the drug/s in "spice" have never been tested in humans and can be 1000x more powerful than marijuana. They can cause seizures, dissociation, severe anxiety, panic, psychosis, etc--sometimes chronic.