They are banned in 41 states, yet are readily available in stores nationwide:

Best known by the street names “Spice” or “K2,” fake weed is an herbal mixture sprayed with chemicals that’s meant to create a high similar to smoking marijuana, according to the National Institute on Drug Abuse. Advertised as a “legal” alternative to weed, it’s often sold as incense or potpourri and in most states, it’s anything but legal.

 

Christina Zdanowicz at CNN.com runs some numbers:

Synthetic marijuana was linked to 11,406 drug-related emergency department visits in 2010, according to a first-of-its-kind report by the Substance Abuse and Mental Health Services Administration. This is when it first started showing up on health providers’ radar, as the Drug Abuse Warning Nework detected a measurable number of emergency visits.

Who wound up in the emergency room the most? Children ages 12 to 17.

 

The symptoms that users of synthetic weed display differ significantly from the real thing:

Common side effects to smoking synthetic marijuana include bloodshot eyes, disturbed perceptions and a change in mood, said Dr. Melinda Campopiano, a medical officer with the Substance Abuse and Mental Health Services Administration.

“People can become very agitated or can be come unresponsive — conscious but not reacting normal to situations,” she said. They may also appear paranoid or describe hallucinations. Some of the more potentially serious effects include an elevated heart rate and elevated blood pressure.

Campopiano said she had never heard of a patient having a stroke in these circumstances, but she described how high blood pressure could lead to one.

 

Zdanowicz profiles a teenager from Chicago who did suffer a stroke from smoking synthetic marijuana here.

Read report from Substance Abuse and Mental Health Services Administration (SAMHSA) about synthetic cannabinoids here.

More information from the NIH here.