Synthetic marijuana is a catch-all term covering a variety of technically legal drugs that mimic the effects of THC, the active ingredient in real marijuana. Vox's German Lopez has a great explainer on the topic if you want to read up on it. Synthetics have grown in popularity in recent years, particularly among teens and young people - males especially. Part of the appeal is that they're easy to get - various formulations are often sold in convenience stores.
Synthetics are said to produce a high similar to marijuana's, but due to the mix of potent and often toxic chemicals they contain, they come with a whole host of nasty side effects. For a sense of how they affect different people, it's instructive to leaf through some of the first-hand accounts at erowid.org, an online clearinghouse for information about drugs. Among the accounts, which are completely anonymous and by no means verifiable, there are more than twice as many bad trips as there are positive experiences. One user characterized it as "basically cannabis, minus the fun." Another called it "a trip worse than hell."
Because of the high prevalence of side effects and the uncertainty behind what you're actually getting, it's unlikely that synthetics will ever enjoy real marijuana's widespread popularity. But because of the ease of obtaining it, people will likely keep trying it out - even if they end up regretting it. The Monitoring the Future survey reports that in 2013, about 8 percent of 12th graders had tried synthetic marijuana in the past year. This represents a significant number, but it's well behind alcohol, tobacco, marijuana and prescription drug use in that age group. The survey also shows that use of synthetics among high schoolers dropped sharply between 2012 and 2013.
There's a bigger lag on SAMHSA's emergency department data, which is why we're only seeing the 2011 figures now. Those numbers show that men are twice as likely as women to go to the ER for synthetic weed, and that young people are much more likely than older people to do the same.
But it's important to note that synthetics only account for a small fraction of total emergency department visits involving drugs: they made up a little over 1 percent of the roughly 2.5 million drug-related visits in 2011. Because we don't currently have good numbers on how many people are using synthetics, it's not clear what proportion of synthetic users are ending up in the hospital, or how that proportion compares to other drugs.
Jacob Sullum argues that prohibitionist policies on real marijuana are driving people to try the more dangerous synthetic stuff:
Thanks to our drug laws, Cloud 9 [one brand of synthetic marijuana] has certain advantages over marijuana: You can buy it cheaply in convenience stores without risking arrest, for instance, and it will not get you thrown out of school or fired from a job because of a positive drug test. To the extent that marijuana prohibition creates a niche for products like Cloud 9, it is driving people away from a well-researched drug that humans have been consuming for thousands of years and toward experimental compounds with unpredictable hazards.
There's a certain logic to this. I'd also add that humans are generally novelty-seeking creatures. If a new psychoactive experience presents itself and it's easy to obtain (as with synthetic weed), a certain percentage of people will be tempted to try it out regardless of the availability of other drugs.
Still, there's little doubt that one of the primary draws of synthetic weed is its alleged similarity to real marijuana. Many of the use accounts at erowid.org assess synthetics according to how well they do or don't mimc the effects of real weed. It stands to reason, then, that more widespread and safer access to real marijuana would eliminate one of the main factors driving kids to try out the more dangerous fake stuff.