http://www.narconon.org/drug-information/synthetic-drugs.html
This on Spice.
Spice was purported to be a legal replacement for cannabis and was often sold as incense in head shops. Instructions for use specifically state that the product was not for human consumption but that fooled no one. Spice, also known as K2, is composed of one or more chemicals sprayed onto herbal material. These chemicals are known only as HU-210, JWH-018 or JWH-073, among others.
Besides being legal in the US until 2012, Spice would not show up on many existing drug tests in the early days of its distribution. It found popularity among some members of the military, but this was short lived. In 2011, more than 1,500 sailors were relieved of duty after being found to be using Spice. The military had to scramble to update drug tests and institute drug abuse monitoring programs in part due to the internal crisis created by Spice abuse.
Spice was found to cause anxiety, hallucinations, psychosis and paranoia in some users. Several deaths were associated with Spice, often because of paranoia or violence triggered by use of the drug. But lack of drug tests for Spice in the early days of its distribution made accurate reporting on resulting deaths impossible.