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April 11, 2002

Marijuana Use Linked to Hallucinogen Use

Young Marijuana Smokers More Likely to Have the Opportunity to Use Hallucinogens

A study from the Johns Hopkins Bloomberg School of Public Health provides the first epidemiologic evidence that young marijuana smokers are substantially more likely than non-smokers to be presented with the opportunity to try hallucinogens. Once the opportunity for hallucinogen use occurs, marijuana smokers are more likely than non-smokers to try hallucinogens. The study appears in the April 2002 issue of the journal  Drug and Alcohol Dependence.

"Research in the past has focused on the causal relationships of drugs, but our study is the first to support the idea of two separate mechanisms linking marijuana and hallucinogen use -- that of increased opportunity and increased use once given the opportunity," says lead author Holly Wilcox, a doctoral candidate in the department of mental health at the Johns Hopkins Bloomberg School of Public Health. "Insight into this area teaches us about mechanisms that might help guide new progress for prevention of drug problems."

For the investigation, the researchers used self-report data from more than 40,000 young participants in the 1991 to 1994 National Household Surveys on Drug Abuse (NHSDA). From these data, they were able to extract information about the age at which young people first had the opportunity to use different drugs and the age at which they first tried them. They focused on the availability and use of two drugs: marijuana (cannabis, reefer, blunts, hash oil, or any other form of marijuana) and hallucinogens (LSD, mescaline, mixed stimulant-hallucinogens, and PCP).

The results showed that by age 21, almost one-half of the teenagers who had smoked marijuana had a chance to try a hallucinogen, compared to only one in 16 of the teenagers who had never smoked marijuana. Within a time period of one year after the first chance to use a hallucinogen, two-thirds of marijuana smokers actually tried one, compared to only one in six of the teenagers who had never smoked marijuana.

"This large difference between marijuana smokers and non-smokers may be attributed to the social influences in a marijuana smoker's life. Young people who are using marijuana sometimes develop contacts with illegal drug dealers who may try to push other drugs like Ecstasy or LSD," explains James C. Anthony, PhD, a professor of mental health, psychiatry, and epidemiology at the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins University School of Medicine.  "Also, marijuana smokers often are members of social circles where drug use and experimentation are more common, and friends are likely to share drugs. In addition to trying to persuade young people to not use drugs, it may be worthwhile for us to persuade users to not share their drugs with friends."

The authors say further research is needed to account for variations in exposure opportunities experienced by marijuana smokers and to understand why some marijuana smokers choose not to use hallucinogens once given the opportunity. "Such research should lead toward new ideas for prevention of hallucinogen use," concludes Ms. Wilcox.

Holly C. Wilcox, Fernando A. Wagner, and James C. Anthony contributed to the research and writing of the article, "Exposure opportunity as a mechanism linking young marijuana use to hallucinogen use."

The study was supported by grants from the National Institute on Drug Abuse (NIDA) and support from the National Council on Science and Technology (CONACYT), Mexico.

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Public Affairs Media Contacts for the Johns Hopkins Bloomberg School of Public Health: Ming Tai or Tim Parsons @ 410.955.6878 or paffairs@jhsph.edu.