Unpacking the Gateway Drug Theory

by Maximilian Eyle

The Gateway Drug Theory suggests that people who start using marijuana will go on to use more dangerous drugs. The argument that marijuana is a “Gateway Drug” is probably the most popular argument against the legalization of marijuana.

The gateway theory argues that because heroin, cocaine and methamphetamine users often used marijuana before graduating on to harder drugs, it must be a “gateway” to harder drug use. This theory suggests that marijuana infects people with a desire to take harder drugs.

There is absolutely no evidence that this is true but yet marijuana prohibitionists trot it out regularly. Even the DEA has come to admit that, “Little evidence supports the hypothesis that initiation of marijuana use leads to an abuse disorder with other illicit substances.”

The reason that it sounds believable to many people is that people don’t always understand the difference between “correlation” and “causation”. Sure most heroin addicts used to smoke marijuana… but they also used to smoke cigarettes, eat bread, and drink alcohol. The more important statistic is the proportion of marijuana users who later went on to use heroin, and this number is very low. Just because one thing comes before another does not mean it caused it. As the scientific axiom states: correlation does not imply causation.

In fact, the research shows the opposite: the vast majority of marijuana users do not go on to use hard drugs. Even the Institute of Medicine of the National Academy of Sciences wrote: “There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs”. The “Gateway Theory” is raised again and again, even the Governor recently cited it as a reason for maintaining marijuana prohibition.

In addition to the gateway theory having been debunked, researchers from the Johns Hopkins Bloomberg School of Public Health found that opioid overdose deaths had gone down by an average of 25% in states where marijuana was legally available. This is because those people at risk for opioid abuse had a safer alternative available to them. This suggests an effect that some call the “reverse gateway”, where increased availability of marijuana prevents people from using more dangerous drugs.

Maximilian Eyle is a native of Syracuse, NY and a graduate of Hobart and William Smith Colleges. He has experience working in the drug policy field and writes about it every month for CNY Latino. Maximilian learned Spanish while living in Spain where he studied and worked as an English teacher.