A significant amount of data has been generated in recent years showing that cannabis access is associated with reduced levels of opioid use and abuse. But emerging data also indicates that many patients similarly substitute marijuana for a variety of other substances, including alcohol, tobacco and benzodiazepines.

Last month, a team of researchers from Canada and the United States surveyed over 2,000 federally registered medical cannabis patients with regard to their use of cannabis and other substances. (Medical cannabis access has been legal across Canada for nearly two decades).

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Investigators reported that nearly 70 percent of respondents said that they substituted cannabis for prescription medications, primarily opioids. Forty-five percent of those surveyed acknowledged substituting cannabis for alcohol and 31 percent of respondents said that they used marijuana in place of tobacco.

Among those who reported replacing alcohol with cannabis, 31 percent said they stopped using booze altogether, while 37 percent reported reducing their intake by at least 75 percent. Fifty-one percent of those who reported substituting cannabis for tobacco said that they eventually ceased their tobacco use completely.

This documentation of cannabis substitution is not unique. A 2017 study of medical cannabis patients similarly reported that 25 percent of the cohort reported substituting cannabis for alcohol, while 12 percent substituted it for tobacco. A 2015 paper published in the journal, "Drug and Alcohol Review" also reported that over half of patients surveyed substituted marijuana in lieu of alcohol. A placebo-controlled clinical trial performed by researchers at London’s University College reported that the inhalation of CBD — a primary component in cannabis — is associated with a 40 percent reduction in cigarette consumption.

Numerous studies also indicate that legal cannabis access is associated with reductions in overall prescription drug spending. While much of this reduction is the result of the reduced use of opioids, studies also report decreases in patients’ consumption of other prescription drugs, such as sleep aids, anti-depressants and anti-anxiety medications. A 2019 study by a team of Canadian researchers reported that the use of marijuana is associated with the discontinuation of benzodiazepines. (The popular anti-anxiety medication was responsible for over 11,500 overdose deaths in the United States in 2017, according to the US Centers for Disease Control). In their study of 146 subjects, the initiation of medical cannabis resulted in significant and sustained reductions in patients’ use of the drug.

By the trial’s conclusion, 45 percent of participants had ceased their use of benzodiazepines. In a separate study, also published this year, of over 1,300 US medical cannabis patients suffering from chronic pain conditions, 22 percent reported substituting marijuana for benzodiazepines.

These scientific findings run contrary to the so-called "gateway theory" – the long-alleged notion that marijuana exposure primes users to ultimately engage in the use of far more intoxicating and addictive substances. By contrast, for many people cannabis appears to act as an "exit drug" away from potentially deadly pharmaceuticals, booze, cigarettes and even other illicit substances such as cocaine.

As more jurisdictions move away from cannabis prohibition and toward a system of regulated access it will important to monitor the degree to which these trends continue and to assess their long-term impacts on public health and safety.

Paul Armentano is the deputy director of NORML — the National Organization for the Reform of Marijuana Laws. He is the co-author of the book, Marijuana Is Safer: So Why Are We Driving People to Drink? and the author of the book, The Citizen’s Guide to State-By-State Marijuana. Laws.