Ask Dr. Leigh: Is Cannabis a Gateway Drug?


Using cannabis can have a big impact on your physical and mental health—for better, and sometimes for worse. That’s why it’s important to consult a healthcare provider before experimenting.

Here at GreenState, cannabis clinician Dr. Leigh Vinocur is here to answer your questions on healthy living with cannabis.

Editor’s Note: The answer to this question is meant to supplement, not replace, advice, diagnoses, and treatment from a healthcare provider.  Always consult a medical professional when using cannabis for medicinal purposes, and do not disregard the advice of your healthcare provider because of anything you may read in this article. 

Q: Is cannabis a gateway drug?

A: The short answer, for me, is that I do not believe that there is a preponderance of evidence that supports this notion that use of marijuana or cannabis, leads to use of other “hard drugs” such as heroin or cocaine.

But for my long-winded answer, let’s first look at the history of this theory. In the 1970’s Denise Kandel, a sociologist and researcher in New York state, described a sequencing in the use of substances during a longitudinal study of secondary school children.  She described these children moving from tobacco and alcohol to cannabis and then other substances, which became known as the gateway hypothesis. It continued to be popularized during the 1980s in the Regan administration’s war on drugs with their “Just Say No Campaign”.  The presumption is a predictable sequence of initiations leading from the use of one drug, usually legal, such as tobacco or alcohol to then softer (but illicit at the time) drugs like marijuana and eventually to hard drugs such as heroin or cocaine. However, many took this correlation to assume it means causation, despite Kandel herself admitting that there was no causal relationship, and it was only an observed association.  So, if you are describing a hypothesis that relies on a sequential progression from one condition to the next, it really should imply that the preceding condition caused the secondary condition. Therefore, right from the start, this gateway theory argument is faulty.

Additionally, much of the scientific research used to help support this theory was extrapolated from animal studies. They looked at dopamine, the pleasure and reward chemical in the brain, and its changes with respect to THC in these adolescent rat brains measured by their propensity to self-administer THC.  However, most clinicians and researchers do recognize that animal data is potentially fraught with problems related to its interpretation when trying to crossover and compare to humans.

As humans, our behaviors do not occur in a vacuum and cannot be easily tested via mazes and self-administration the way we do with animals. Even with epidemiological studies, it is hard to find completely supportive evidence for the gateway theory. These studies cited that this theory only reflects an association, and not a cause-and-effect relationship of a specific drug such as cannabis causing the subsequent use of other more addictive drugs.

And when we look at numbers alone, they don’t add up for the gateway theory. According to a 2014 global report on addiction, 20% of the global population smokes tobacco, often the first drug described in the gateway series.  So, if the total population at that time of this report was 7.3 billion people that would mean that about 1.5 billion people use tobacco. This same report showed that 3.5% of the global population used cannabis, that would have equated to about 255,500,000 million. However, looking at these 2 documented gateway drugs, they found only 15 million people worldwide had graduated on to use intravenous “hard drugs.” It would seem that in reality there are very few substance users (tobacco and cannabis) who then actually move on to use more addictive dangerous harder drugs. Therefore, there must be something more than just exposure to these supposed gateway drugs. In fact, even today the National Institute on Drug Abuse, NIDA acknowledges on their website that the majority of marijuana users do not go on to use other, “harder” substances.

We should not be focusing on the “what”, what substance is being used. With the disease of addiction, we need to understand the underlying issues of the “why”. Why did that a person becomes addicted to a substance, this is called the common liability theory.

Health care agencies, parents, physicians, educators, and therapists need to focus on the real issues causing substance use disorder.  It is more related to the interplay of things such as mental and psychological problems that are often caused by past traumas that are not being addressed, or their specific genetics and family history, as well as the socioeconomic issues, crime rates in areas where these children live and peer group pressures along with any bullying they might be enduring. This is more important than any initial substance they may have used or experimented with. All of this contributes to a person’s use of a substance whether it is for self-medication or escape.

Substance use disorder is a complicated life-long chronic brain disease that albeit may in fact also be due in part to changes in our brain chemistry from the substance. But it is the complex interplay of all factors, and it requires intervention at many points, not just their first use of a supposed “gateway substance.” Unfortunately, in my practice of emergency medicine these last 25 years has shown me that taking a simplistic approach to “just say no” to that first substance, has not been proven to work nor to address this huge problem of substance abuse that we still have today in our society.

Got cannabis questions? Ask Doctor Leigh. Send your questions to GreenState’s Assistant Editor Elissa Esher at and keep an eye out for new answers from Dr. Leigh Vinocur every month.

Dr. Leigh Vinocur is a board-certified emergency physician who also has a cannabis consulting practice for patients and industry. She is a member of the Society of Cannabis Clinicians and a graduate of the inaugural class, with the first Master of Science in the country in Medical Cannabis Science and Therapeutics from the University of Maryland School of Pharmacy.

The response to this question was not written or edited by Hearst. The authors are solely responsible for the content.

Leigh Vinocur, MD