Is Marijuana a Gateway Drug?

The impact of cannabis on people and society has long been disputed, with researchers and politicians alike continuing to debate the substance and its safety. Propaganda in past decades has promoted cannabis as a gateway drug, saying that it can lead to harder drug use and addiction in the future.

According to Donald Trump’s former Attorney General William Barr, it is. In September, Barr published an op-ed for Fox News in which he stated: “Not all marijuana users go on to use harder drugs, but the vast majority of people who use harder drugs started with marijuana.”

Barr voiced these opinions about cannabis as a means of slamming the Biden administration’s proposal to reschedule marijuana federally, moving cannabis from Schedule I to Schedule III under the Controlled Substance Act (CSA). 

But is marijuana actually a “gateway drug?” Barr is far from the first person to make this claim. In 1938, his predecessor Henry Anslinger first publicly promoted the idea that cannabis use leads to heroin addiction, as well as dementia and crime, in order to stricten police enforcement and target minorities. 

To find out more, we’ll look into the current science and see what the experts say. 

Is Weed a Gateway Drug? Some Say Yes

As explained by the Centers for Disease Control (CDC), researchers do not agree on whether or not cannabis is a gateway drug, given limited evidence. Some researchers, however, have interpreted data on cannabis usage to mean that it is indeed a gateway drug, particularly if they start cannabis before age 16 or have cannabis use disorder.

RAND explains, for example, that three pieces of information have been used to support this notion: 

• First, marijuana users are more likely than nonusers to move on to hard drug use 
• Second, nearly all who have used both marijuana and hard drugs started using marijuana before the hard drugs 
• And third, that a greater frequency of marijuana use corresponds with a greater likelihood of using hard drugs later 

Others Say No

Other evidence, however, points to the opposite conclusion. The National Institute on Drug Abuse states that “most people who use or have used cannabis do not go on to use other substances later in life.” This can be interpreted as evidence refuting the idea that cannabis is a gateway drug. 

A 2021 study also examined this question through the lens of recreational marijuana laws (RMLs). The studies, “show that RMLs increase adult marijuana use and reduce drug-related arrests over an average post-legalization window of three to four years. There is little evidence to suggest that RML-induced increases in marijuana consumption encourage the use of harder substances or violent criminal activity, and some evidence that RMLs may aid in reducing opioid-related mortality.” 

In other words, the increase in marijuana usage was not found to increase the use of harder drugs. In fact, it’s just the opposite, which stands in contrast to the notion of cannabis as a gateway drug. 

Additionally, many drug users initiate their drug experiences with drugs other than cannabis. A 2013 study of marijuana users found that 80% of participants began with alcohol or tobacco, and 33% began with another drug prior to marijuana. 

Correlation Vs. Causation

Ultimately, much of the debate comes down to correlation or causation. While cannabis is associated with harder drugs in some respects, there are many possible explanations for this association, and it does not inherently mean that cannabis usage causes harder drug usage. It’s more likely that people find themselves in difficult socioeconomic circumstances, which leads them to try coping with one or more drugs, including cannabis.

A 2009 study outlines some alternative reasons for these positive associations. These include: 

1. The selective recruitment to heavy cannabis use of persons with pre-existing traits (that may be in part genetic) that predispose to the use of a variety of different drugs; 
2. The affiliation of cannabis users with drug-using peers in settings that provide more opportunities to use other illicit drugs at an earlier age; 
3. Supported by socialization into an illicit drug subculture with favorable attitudes towards the use of other illicit drugs.” 

Similarly, RAND explains, “Those who use drugs may have an underlying propensity to do so that is not specific to any one drug. There is some support for such a ’common-factor’ model in studies of genetic, familial, and environmental factors influencing drug use.”

In other words, people who use both cannabis and harder drugs may be influenced by certain factors including genetics and socialization that pertain to drugs overall, and it doesn’t mean that cannabis is causing or acting as a “gateway” to these other drugs. 

Final Thoughts

So, is cannabis a gateway drug? While there is no inarguable yes or no answer, there has been no definitive evidence found supporting the notion that it is. There’s a web of complex societal and economic factors that drive polysubstance use.

Many cannabis users never go on to use harder drugs, even though some users do. Ultimately, all drug usage should be done safely and with an awareness of one’s limits.