Cannabis legalisation does not lead to increases in the use of other drugs such as alcohol, cigarettes and opioids, suggesting that the long-touted ‘gateway theory’ about cannabis is not based in relality.
Researchers at the University of Washington assessed trends in alcohol, nicotine and non-prescribed opioid use following the 2012 cannabis legalisation in Washington State.
After assessing 12,500 young adults aged 18 to 25, authors of the study found that adolescents actually consumed less alcohol and cigarettes, along with other substances.
The authors concluded, “Our findings add to the evidence that the legalisation 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 legalisation and the evolution of legalised cannabis markets may be specific to cannabis use and related consequences.”
The gateway drug theory
Supporters of the gateway drug theory argue that ingesting cannabis will inevitably lead to the use and misuse of other illicit drugs, which may include cocaine, methamphetamines, and opioids, such as heroin.
Those who support the theory seek to ban cannabis and penalise the people in possession of it – suggesting that it’s extremely dangerous, leads to substance use disorder, and alters brain chemistry.
But even if weed was to be a gateway drug, the evidence doesn’t seem to suggest that prohibiting it would stop the use of any other drugs.
What the research tells us
The latest study from Washington has shown a decrease in alcohol and cigarette use, as well as the misuse of pain-relievers in the last year.
According to authors of the study, “the implementation of legalised non-medical cannabis coincided with decreases in alcohol and cigarette use and pain reliever misuse.”
A comment on the study’s findings from NORML’s Deputy Director, Paul Armentano, read: “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,” he added.
The RAND Corporation and the National Academy of Sciences have carried out many studies to challenge the gateway drug claims, with one study concluding: “Cannabis has no causal influence over hard drug initiation.”
This 2019 study also suggests that there was no correlation between recreational or medical use of cannabis and the changes in opioid overdose mortality.
And a study in 2021 used 18 tests to find the evidence that would support cannabis as a gateway drug.
However, only three of the tests showed substantive results for a link between cannabis use and the misuse of other drugs.
What’s more, researchers from the study have warned that the three tests were subject to hidden bias – so in other words – the study didn’t provide any evidence for cannabis being a gateway drug.