Synthetic cannabinoids ("synthetic marijuana"), with names like Spice, K2, Scooby Doo and hundreds of others, are often sold as a "legal" alternative to marijuana. Often perceived as a safe legal alternative to illicit drug use, synthetic marijuana use was associated with 11,561 reports of poisonings in the United States between January 2009 and April 2012.

Popular among teens, in 2011, synthetic marijuana was used by more than one out of ten (11.4%) high school seniors in the US, making it the most commonly used drug after real marijuana.

A new study by researchers affiliated with New York University's Center for Drug Use and HIV Research (CDUHR), is now online ahead of print in Drug and Alcohol Dependence and it is one of the first national studies to examine risk factors for use of synthetic marijuana among a large, nationally representative sample of teens.

"Use began to decrease last year, but the drug still poses a substantial threat, and research was needed to determine which teens are at highest risk for use," said Joseph J. Palamar, PhD, MPH, a CDUHR affiliated researcher and an assistant professor of Population Health at NYU Langone Medical Center (NYULMC).

The study, "Synthetic Cannabinoid Use in a Nationally Representative Sample of US High School Seniors," used data from Monitoring the Future (MTF), a nationwide ongoing annual study of the behaviors, attitudes, and values of American secondary school students. The MTF survey is administered in approximately 130 public and private schools throughout 48 states in the US. Roughly 15,000 high school seniors are assessed annually. This study examined data from 11,863 students who were asked a variety of questions to gauge their use of natural and synthetic marijuana from 2011 to 2013.

The researchers found that race and sex were significantly correlated with synthetic marijuana use. Compared to females, males were consistently at greater risk for synthetic marijuana use and more frequent use. Black students were 42% less likely to report synthetic marijuana use and 36% less likely to report more frequent use than white students.

"However, when we factor in other drug use, we find that identifying as a racial minority no longer remains a protective factor," explained Dr. Palamar. "The data also showed that students who go out four to seven nights per week for fun were at high risk for experimenting and for continuing use. More research is needed, but this may be due to increased exposure to others who use these products during these nightly activities."

The researchers also found that students who engaged in the use of other substances were more likely to use synthetic marijuana. Lifetime use of alcohol nearly doubled the odds for use. Cigarette smoking increased risk for synthetic marijuana use, particularly regular smoking either in the past or in the present, both of which more than doubled the likelihood of use. Reporting lifetime use of any illicit drug other than natural marijuana more than doubled the odds for use.

Most importantly, frequency of lifetime marijuana use was the strongest correlate, with more frequent use further increasing odds of synthetic marijuana use.

"Our main finding was that very few never-users of natural marijuana have ever tried synthetic marijuana," said Dr. Palamar. "Only 0.5% of non-marijuana users reported use. Although we were unable to determine whether use of natural marijuana tended to occur before synthetic marijuana, results do suggest that it is mainly marijuana users who are at greatest risk for use."

Dr. Palamar posits that it is likely that many of these synthetic marijuana users resort to trying this "legal," but more dangerous version of marijuana in order to avoid possible arrest, detection on drug screenings, or the stigma associated with being an illicit drug user.

The results from this study can be used to inform national and local efforts to prevent use and adverse consequences resulting from use. According to the researchers, further investigation is needed to determine if synthetic marijuana serves as a gateway drug to natural marijuana and other illicit drugs. The researchers also mention that research is needed to determine whether teens are still turning to this more dangerous form of marijuana in states where recreational marijuana use is now legal for adults to use.

Researcher Affiliations: Joseph J. Palamar, PhD--NYULMC, Department of Population Health; NYU CDUHR; Patricia Acosta, BA--NYULMC, Departments of Population Health and Child and Adolescent Psychiatry.

Declaration of Interest: The authors declare no conflict of interest.

Acknowledgements: The authors would like to thank the principal investigators of Monitoring the Future (PIs: Johnston, Bachman, O'Malley, and Schulenberg) at The University of Michigan, Institute for Social Research, Survey Research Center, and the Inter-university Consortium for Political and Social Research for providing access to these data. Monitoring the Future data were collected through a research grant (R01 DA-01411) from the National Institute on Drug Abuse (NIDA). Dr. Palamar's research on use of new and emerging psychoactive drugs is also now supported by NIDA (K01 DA-038800).