Cannabis commercialisation not decriminalisation drives up usage, study finds | Cannabis

One review found that while decriminalizing cannabis possession or tightly regulating access to the drug did not appear to increase use, when the drug was sold commercially the number of users increased and there were more mental health problems.

An international team analyzed the dramatic shift in cannabis-related policies between 2000 and 2025; This includes how the number of people taking the drug, the potency of marijuana and how rates of psychosis have changed since the new rules came into force.

Researchers found that places that have opened commercial markets for marijuana, such as the United States and Canada, saw more users and an increase in drug potency. They also found that more people were visiting the hospital for drug-induced psychosis and other mental health problems.

Where cannabis was decriminalized in Europe, Africa, Oceania and Asia, there was little evidence of any change in use or psychiatric illness. A similar experience occurred in Uruguay, where marijuana was legalized but tightly controlled by the state.

“Looking globally, we see a rapid shift towards more liberal cannabis policies,” said Tom Freeman, professor of psychology at the University of Bath and first author of the review. “This gives us a chance to evaluate what happens from before to after in terms of marijuana use, marijuana addiction, and marijuana-related psychiatric disorders.”

Freeman said the findings were published on: Lancet PsychiatryIt was “encouraging” for policymakers considering decriminalizing marijuana or tightly regulating the drug in legal markets. But the impact of the open market, where drugs were sold in a similar way to alcohol and tobacco, had a very different effect.

“Given the long history of alcohol and tobacco use, it’s too early for any of these policy changes, but that’s the way it’s evolving,” he said.

“When there is a for-profit industry, especially for an addictive product, there is an incentive to sell cheaper products and high-potency products because they know the more they sell, the more money they will make, which can increase usage,” added Freeman. “We have a long history of the tobacco and alcohol industries being difficult to regulate, resulting in increased sales and greater harm to those who use these products.”

In the UK, cannabis is a class B drug and the maximum penalty for possession without a prescription is imprisonment for up to five years, an unlimited fine, or both. Last year, a report by the London Drugs Commission, commissioned by London Mayor Sadiq Khan, argued that sanctions were unfair and recommended decriminalizing recreational possession. Black people are five times more likely to be stopped and searched on suspicion of drug-related crimes than white people, the report found.

Uruguay became the first country to fully legalize marijuana in 2013, but the market remains tightly controlled by the state. Adults who register can purchase the drug at a pharmacy, through a cannabis social club, or grow it at home. It allows the government to control the size of the market as well as the safety of the products.

Sir Robin Murray, professor of psychiatric research at King’s College London, said it was early days to understand the full effects of global cannabis policies, but added there was now consensus that commercialization of supply, rather than simple legislation for recreational use, was the “critical factor”.

“Unfortunately, in North America, legalization was followed by widespread commercialization, facilitated by advertising from companies that, at their peak, wanted to sell marijuana as well as tobacco,” he said. “Is it possible to legalize without commercialization in Western capitalist countries? It should be possible, but so far no country has achieved this due to the growing power of the multi-billion cannabis industry.”

Alex Stevens, professor of criminology at the University of Sheffield, said the review was “absolutely essential” for policymakers looking at ways to tackle drug use. “We’re getting a pretty consistent message from the research that restrictive regulatory models and decriminalizing possession will not necessarily lead to increases in use,” he said. “Opponents of these reforms always say: If you let people use it, then use will go up a lot, but that’s not what we’re seeing in any of the countries that are doing this.”