Marijuana, also known as cannabis or weed, is the most commonly used -- and abused -- illicit drug. It is often thought of as a "soft drug," with proponents claiming that it is non-addictive and relatively harmless, particularly when compared with the much more available and socially acceptable drug, alcohol.
What is a "Gateway Drug?"
The gateway drug theory states that "soft drugs," such as marijuana, provide an apparently safe psychoactive experience that makes naive users more open to experimenting with other illicit drugs. Because most people who develop severe problems with drugs, such as cocaine, meth, and heroin, had early experiences with marijuana before trying these other drugs, and because marijuana use is correlated with use of other drugs, the argument goes that if they had not taken marijuana in the first place, they would not have been lured into a false sense of security around drug use and so would never have "progressed" to other, more harmful substances.
The Marijuana Legalization Debate
In spite of marijuana having a reputation for being a non-problematic substance, and even being beneficial in the context of medical marijuana, some have argued that the biggest harm marijuana poses is its function as a gateway to other drug use. By their exposure to illict drug use in the form of marijuana, young people are introduced to the world of drug use and to drug dealers who have other "hard drugs" to offer, such as LSD, cocaine, and heroin.
Ironically, the gateway drug theory of cannabis has been used to support both sides of the debate on whether marijuana should be legalized. The anti-legalization lobby argue that marijuana's status as a gateway drug makes it more dangerous to users in the longer term, by introducing them to the experience of scoring, possessing and consuming an illegal drug.
Meanwhile, the pro-legalization lobby argues that it is the illegal status of the drug, combined with its relative harmlessness, that makes it uniquely positioned as a gateway to other illegal drug use. They argue that if marijuana were legal, it would no longer be a gateway drug, as users could purchase the drug through legal channels and thus not be exposed to "hard drugs."
Is Marijuana Harmless?
The relevance of the gateway drug theory rests on the premise that marijuana is harmless, which is incorrect. But this does not provide much support for the argument that marijuana is not a gateway drug, because to make that argument, it would have to be admitted that marijuana is potentially harmful in its own right, and the anti-legalization movement could then simply shift their emphasis to the direct harms caused by marijuana. As this does not support the goals of the pro-legalization side, proponents tend to stick to the view that marijuana is, to all intents and purposes, harmless, and the harms it causes arise from its illegal status.
Does Marijuana Lead to Other Drug Use?
Extensive reseach into the relationship between cannabis use and other drug use has only partially answered this question. Studies indicate that some people have a partially genetic predisposition to drug use, and that they are more likely to become heavy cannabis users. However, this finding doesn't particularly support the view that exposure to cannabis leads to other drug use.
The social aspects of the gateway drug theory are supported by evidence that cannabis users socialize with drug-using peers in settings that provide more opportunities to use other illicit drugs at an earlier age, and that this forms an illicit drug subculture with positive attitudes toward the use of other illicit drugs.
The Gateway Theory Cannot be Proved
The actual prevalence of drug use is impossible to measure, and studies of drug use are fraught with inaccuracies, so there is no way of knowing whether marijuana and use of other drugs are consistently related. Certainly, there are many people who use marijuana and do not progress to other drug use, as well as many who do. Even if it was proved that users of marijuana were significantly more likely to use other drugs, there is no way of knowing whether it was because of the "gateway" role of marijuana, whether there were other factors at play, or because the individuals involved simply used whichever drugs were available to them.
The Bottom Line
Don't automatically assume that your son will progress to other drug use if he is using marijuana. But don't igore the possibility, or assume that his marijuana use won't lead to problems. Follow my tips for preventing addiction in your kids, especially by setting appropriate boundaries, such as no smoking in your home. And be willing to support your son in seeking help, if he needs it.
Fergusson, D., Boden, J. & Horwood, L. "Cannabis use and other illicit drug use: testing the cannabis gateway hypothesis." Addiction 101:556–569. 2006.
Hall, W. & Lynskey, M. "Is cannabis a gateway drug? Testing hypotheses about the relationship between cannabis use and the use of other illicit drugs." Drug and Alcohol Review 24:39-48. 2005.
Morrall, A., McCaffrey, D. & Paddock, S. "Reassessing the Marijuana Gateway Effect." Addiction 97:1493–1504. 2002.