Marijuana used to be legal for most of human history until the early 20th century. In the U.S., cannabis was made illegal across the country once the Marijuana Tax Act of 1937 was adopted by Congress. To this day cannabis is illegal at the federal level, but most U.S. states have legalized the use and sale of medical marijuana, and around half of these states went all the way and legalized recreational use.

While the notion that marijuana is a ‘gateway’ drug to the use of other, potentially more dangerous controlled substances like opium and cocaine has been thoroughly debunked by many studies, many feared that legalization would cause an uptick in the use of other drugs. But, if anything, the reverse seems to be true.

In a recent study, scientists at the University of Washington assessed the trends in the use of alcohol, nicotine, and non-prescription pain medication in Washington State following cannabis legalization. The study involved 12,500 young adults between the ages of 18 and 25.

According to the results, the prevalence of alcohol use within the past month, heavy episodic drinking, cigarette use, and past-year pain reliever misuse decreased. However, the prevalence of e-cigarette use increased during the timeframe of the assessment, and it’s unclear why exactly. The prevalence of e-cigarette use has been increasing in recent years nationwide, so these trends may be unrelated to marijuana legalization.

“Contrary to concerns about spillover effects, implementation of legalized non-medical cannabis coincided with decreases in alcohol and cigarette use and pain reliever misuse,” the researchers said, adding:

“Our findings add to evidence that the legalization of non-medical cannabis has not led to dramatic increases in the use of alcohol, cigarettes, and non-prescribed opioids. … The findings indicate that the most critical public health concerns surrounding cannabis legalization and the evolution of legalized cannabis markets may be specific to cannabis use and related consequences.”

The notion that marijuana can help people drink less is supported by other research. A 2021 study involving nearly 100 individuals undergoing alcohol treatment found using cannabis helped the patients consume 30% fewer drinks and reduced their risk of binge-drinking episodes by a factor of two. In 2022, researchers at Cornell University used data from Medicaid reporting on prescription drugs from 2011 to 2019, finding marijuana legalization was associated with decreased use of prescription medication for treating anxiety, sleep, pain, and seizures. And in 2019, researchers found that states that have legalized marijuana have experienced a decrease in opioid prescriptions as a result.

“Real-world data from legalization states disputes longstanding claims that cannabis is some sort of ‘gateway’ substance. In fact, in many instances, cannabis regulation is associated with the decreased use of other substances, including many prescription medications,” NORML’s Deputy Director Paul Armentano said in a statement.

The findings appeared in the Journal of Adolescent Health.