A recent study funded by the federal government suggests a potential “substitution effect” linked to marijuana legalization, indicating that young adults in California have significantly reduced their use of alcohol and cigarettes following the enactment of legal cannabis.

Interestingly, the research contradicts arguments from prohibitionists regarding the potential consequences of legalization. One of the leading marijuana myths is that legalization would lead to an increase in use of cannabis by teens and young adults. The data also reveals no significant increase in marijuana use among young adults who were still underage to access retail dispensaries.

Published in the Journal of Psychoactive Drugs last week, the study conducted surveys on individuals aged 18-20 in Los Angeles before and after the state implemented adult-use marijuana legalization in a 2016 voter initiative. The research involved two cohorts: 172 subjects surveyed before legalization between 2014 and 2015, and 139 subjects surveyed after legalization between 2019 and 2020.

The study found that among those surveyed, the use of alcohol and tobacco dropped after cannabis became legal. They also found that other than an increase in the use of cannabis edibles, there was no increase in cannabis use among the young adults surveyed.

The researchers wrote, “Notably, frequency of cannabis use did not significantly differ between the pre-and post-adult use legalization cohorts, except for greater use of edibles, despite potentially greater access to cannabis.”

Study Findings Also Undermine ‘Gateway’ Theory

The study, funded by the National Institute on Drug Abuse, also found that changes in the use of illicit and prescription drugs “did not significantly differ” between pre-legalization and post-legalization cohorts. The researchers made note of this because another concern of those opposed to legalization is that cannabis serves as a gateway drug that leads to abuse of other drugs.

“Future studies should monitor whether stable rates of cannabis use and declines in alcohol and cigarette use will be sustained as some participants reach legal age to access these substances for adult use, and how these trends continue or alter as participants enter later emerging adulthood,” researchers wrote.

The Connection Between Cannabis, Alcohol and Cigarettes

The findings of the study mirror those of past studies that have found where cannabis is legal, use of other substances is reduced. For example, studies have shown that people use few prescription opioids when they have access to legal cannabis to help them manage their pain.

One study found that cancer patients use fewer opioids when in treatment if they can instead use cannabis. Researchers in that study wrote that “medical marijuana could be serving as a substitute for opioid therapies among some adult patients receiving cancer treatment.”

The same has also been found to be the case with alcohol. One study found that Millennials used less alcohol in places where they could legally purchase cannabis. Also, Americans have said in a recent survey that they find cannabis less harmful than alcohol.