Marijuana—also known as cannabis or weed—is the most commonly used illicit recreational drug.1 It is often considered 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. Many people, though—parents especially—may worry about the common idea that marijuana is a gateway drug leading to more challenging and addictive drugs.2

The Gateway Drug Theory

The gateway drug theory states that so-called soft drugs, such as marijuana, provide a safe psychoactive experience that makes naive users more open to experimenting with other, harder drugs.

Most people who develop severe problems with drugs, such as cocaine, meth, and heroin, had early experiences with marijuana before trying these other drugs.3

However, it’s important to note that at the same time, most people who use marijuana will not go on to use these more complex substances.4

Nevertheless, the argument is that if these demanding drug users 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.5

The Marijuana Legalization Debate

Marijuana has come a long way in its reputation for being a non-problematic substance and even being beneficial in the context of medical marijuana. Despite this, some have argued that the most significant harm marijuana poses is its function as a gateway to other drug use.

By their exposure to illicit drug use in the form of marijuana, young people may be introduced to the drug use and to drug dealers with other, harder 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 argues 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.7

Meanwhile, the pro-legalization lobby argues that it is the drug’s illegal status, combined with its relative harmlessness, which makes it uniquely positioned as a gateway to other illicit 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 harder drugs.8

Is Marijuana Harmless?

The relevance of the gateway drug theory rests on the premise that marijuana is harmless, which is incorrect.9 But this does not provide much support for the argument that marijuana is not a gateway drug.

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 shift its emphasis to the direct harm 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, for all intents and purposes, harmless, and the harms it causes arise from its illegal status.10

Does Marijuana Lead to Other Drug Use?

Extensive research into the relationship between cannabis use and other drug use has only partially answered this question. Studies indicate that some people have a partial genetic predisposition to drug use and are likelier to become heavy cannabis users.11 However, this finding doesn’t notably 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 a criminal drug subculture with positive attitudes toward the use of other illegal drugs.12

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 the use of other drugs are consistently related. Indeed, many people use marijuana and do not progress to other drug use, as well as many who do.3

Even if it was proven 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 used whichever drugs were available to them.