According to a report issued by the U.S. Centers for Disease Control and Prevention (CDC), 15 people have died from synthetic marijuana use between January and May of this year - triple the number of deaths from the same time period in 2014. Adverse affects as reported by the National Poison Data System increased 330 percent, and the number of calls to poison control centers has increased by 229 percent.

The federal government considers these substances to be a "growing public health threat that needs to be stamped out," according to Newsweek (via MSN). Just like designer drugs (like Flakka), when one substance is made illegal, manufacturers of the drugs change the formula. Synthetic cannabinoids are man-made psychoactive chemicals sprayed on plant matter and sold in unassuming locales like gas stations, downplaying the risks associated with the drug.

(For more information on Flakka and it's effects, check out HNGN's coverage of synthetic drugs in the "Related Articles" section below.)

"Synthetic cannabinoids include various psychoactive chemicals or a mixture of such chemicals that are sprayed onto plant material, which is then often smoked or ingested to achieve a 'high,'" states the CDC. "These products are sold under a variety of names (e.g., synthetic marijuana, spice, K2, black mamba, and crazy clown) and can be sold in retail outlets as herbal products. Law enforcement agencies have regulated a number of these substances; however, manufacturers of synthetic cannabinoids frequently change the formulation to avoid detection and regulation."

"These synthetic cannabinoids were originally designed as research chemicals for use in the laboratory, trying to identify cannabinoid receptors in the brain, not to be used on the street," said Donna Bush, a forensic toxicology specialist at the federal Substance Abuse and Mental Health Services Administration (SAMHSA), according to Newsweek. The effects can mimic the high of marijuana, but the side effects - like rapid heartbeat, drowsiness, vomiting, agitation and confusion - can be unexpected and last longer.

"You never know what you're getting. Every little bag, every little package can be different because there's no standardization, there's no quality control. These are all products made on the fly," Bush said.

A synthetic cannabinoid called AB Fubinaca was found in the drug Molly that was passed out at a Wesleyan University party. Eleven people were hospitalized, according to The New York Times.

In 2012, President Barack Obama signed into law the Synthetic Drug Abuse Prevention Act, which increases penalties for various synthetic cannabinoid types.