Marijuana is the most prevalent drug in the U.S. Approximately 70% of the 2.8 million individuals who initiated use of illicit drugs in 2013 reported that marijuana was their first drug. Despite extensive research examining potential links between marijuana use and other drug use, the literature is currently lacking data regarding which illicit marijuana users are most likely to engage in use of other illicit drugs.
A new study, published in the American Journal of Drug and Alcohol Abuse by researchers affiliated with New York University's Center for Drug Use and HIV Research (CDUHR), examines how reasons for illicit marijuana use relates to the use of other drugs individually, rather than grouping them into a single "illicit drug" group.
"Aside from marijuana, a wide range of illicit drugs are prevalent, each having different use patterns, and different effects and dangers associated with use," said Joseph J. Palamar, PhD, MPH, a CDUHR affiliated researcher and an assistant professor of Population Health at NYU Langone Medical Center (NYULMC). "Our research helped to identify subtypes of illicit marijuana users who use other drugs, as this may be able to inform prevention efforts."
The cross-sectional study, "Reasons for Recent Marijuana Use in Relation to Use of Other Illicit Drugs among High School Seniors in the United States," draws 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.
Analyses focused on data collected from high school seniors (12th graders), in 12 cohorts (2000-2011; weighted N=6,481), who reported use of marijuana in the last 12 months. The analysis examined self-reported use of eight other illicit drugs: powder cocaine, crack, heroin, LSD, other psychedelics, and nonmedical use of amphetamine/stimulants, tranquilizers/benzodiazepines, and narcotics (other than heroin).
The researchers found that using marijuana to alleviate boredom was associated with increased risk for reporting use of powder cocaine or hallucinogens other than LSD. Nearly a fifth (19.8%) of the sample reported using marijuana for insight or understanding and this reason was also positively related to use of hallucinogens other than LSD. And, 11% reported using marijuana to increase the effects of other drugs; this was a consistent correlate of reporting use of each drug examined in this analysis, even when controlling for sociodemographic and substance use variables.
"Interestingly, we found that using marijuana 'to experiment' decreased risk of reporting use of each of the eight drugs examined before adjusting for other variables," said Palamar. "The marijuana users in this sample who used to experiment were consistently at low risk for use of nonmedical use of prescription narcotics."
Palamar warns that this does not mean that experimenting with marijuana within itself is protective against other drug use. Rather--among recent marijuana users, those who say they're merely just trying it are often at low risk for moving on to other drugs.
Researchers also found that infrequent use in the last year was generally not a risk factor for use of other illicit drugs.
"It seems that only a subset of illicit marijuana users is at risk for use of other illicit drugs," notes Palamar. "Most teens who use marijuana don't progress to use of other drugs and we believe this is evidenced in part by the fact that nearly two-thirds of these marijuana-using teens did not report use of any of the other illicit drugs we examined."
This study highlights different associations between reasons for marijuana use and use of other specific illicit drugs. These results can help inform preventive and education efforts in identifying and targeting specific risk factors in illicit marijuana users with aims to prevent the use of other drugs.
"Programs and education efforts, for example, can benefit from knowing that marijuana users who use because they are bored are more likely to use certain other drugs," said Palamar. "It may be feasible for prevention programs to address ways of coping with factors such as boredom in order to decrease risk."
Palamar notes that research is needed to determine whether legalization and regulation in states such as Colorado further remove marijuana from "street" markets which may contain sources of not just marijuana, but other illicit drugs.
Declaration of Interest: The authors declare no conflict of interest.
Authors and Affiliations: Joseph J. Palamar,1,2; Marybec Griffin-Tomas, 2,3; Dimita Kamboukos, 1
1 New York University Langone Medical Center, Department of Population Health, New York, NY 10016, USA, 2 Center for Health, Identity, Behavior, and Prevention Studies, 3 Global Institute of Public Health New York University, New York, NY.
Monitoring the Future data were collected through a research grant (R01 DA-01411) from the National Institute on Drug Abuse (NIDA), National Institutes of Health (NIH). Dr. Palamar is also supported by NIDA research grant K01-DA038800. The content is solely the responsibility of the authors and does not necessarily represent the official views of the principal investigators, NIH or NIDA. The authors would like to thank the principal investigators (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 (http://www.
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