Former vice president Joe Biden questioned during a Las Vegas town hall this weekend whether marijuana might be a “gateway drug,” despite scant evidence to support that theory.

The 2020 presidential candidate expressed support for medical marijuana and decriminalization of marijuana possession, but said that states should be able to make their own judgments when it comes to legalizing recreational use of of it.

“It is not irrational to do more scientific investigation to determine — which we have not done significantly enough — whether or not there are any things that relate to whether it’s a gateway drug or not,” he said.

But what does the science say? Well, it seems the truth is actually the opposite.

For example, the marijuana compound CBD, or cannabidiol, may help reduce drug cravings in people with heroin addiction, a study suggests. How ironic given the fact that it’s been falsely labelled as the “gateway” drug in recent history.

The study was published on May 21st in the American Journal of Psychiatry, and used 42 people with heroin-use disorder who were attempting to abstain from the drug to conduct their study. The participants were shown “cues” that were used to trigger their drug cravings, this was done in the lab. Video tapes of people using the drug, or objects involved in its rug use were used, among other things. The kicker is, before their lab session the participants received either a dose of CBD or a placebo.

The CBD group reported feeling lower drug cravings when shown the cues, along with a lower level of anxiety compared to those who received the placebo. The effect of the CBD seemed to last up to a week after the drug addicts took the CBD for the study.

Research does not appear to support the “gateway” hypothesis. While some research has found that a large share of people who use marijuana proceed to use other illegal drugs, there’s little evidence to suggest this relationship is causal. “The majority of people who use marijuana do not go on to use other, ‘harder’ substances,” says the National Institute on Drug Abuse (NIDA).

There is absolutely no evidence suggesting that cannabis is a gateway drug.