A new international review suggests that commercial cannabis markets, rather than decriminalisation alone, may be linked to higher cannabis use and more mental health-related harms.
The review examined cannabis policy changes across the world between 2000 and 2025, looking at how different legal approaches affected usage, drug potency, addiction, and psychiatric outcomes. Researchers found that countries or regions that allowed cannabis to be sold commercially, including parts of the United States and Canada, saw increases in the number of users and higher-potency products entering the market.
The study also found that hospital visits related to psychosis and other cannabis-linked mental health problems rose in places where commercial markets expanded. By contrast, areas that decriminalised possession or kept cannabis access under stricter state control did not show the same clear rise in use or psychiatric illness.
The findings were published in Lancet Psychiatry and add to a growing debate over how governments should manage cannabis policy. While many countries have moved away from strict criminal penalties for possession, the review suggests that the way cannabis is made available to the public may matter more than whether possession is legal or illegal.
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Tom Freeman, professor of psychology at the University of Bath and lead author of the review, said the global shift toward more liberal cannabis laws has created an opportunity to study the real-world effects of different policy models. He said the findings were encouraging for policymakers considering decriminalisation or tightly regulated legal access, but warned that open commercial markets appear to produce different outcomes.
The main concern is the role of a for-profit industry. Researchers argue that when companies are allowed to sell cannabis commercially, they have a financial incentive to attract more customers, lower prices, and offer stronger products. Higher-potency cannabis has been linked in previous research to greater risks of dependence and mental health problems, particularly for frequent users.
The review compared this model with countries such as Uruguay, which became the first country to fully legalise cannabis in 2013 but kept the market under strict state control. Adults in Uruguay can access cannabis through registered pharmacies, cannabis clubs, or home growing, allowing the government to limit market size and regulate product safety. Researchers found little evidence that this stricter approach caused a major rise in use or psychiatric harm.
In the UK, cannabis remains a Class B drug, meaning possession can carry a prison sentence, fine, or both. However, some public officials and policy groups have argued that current penalties are too harsh and unevenly enforced. A recent London Drugs Commission report recommended decriminalising possession for recreational use, while also noting racial disparities in drug-related stop-and-search practices.
Experts responding to the review said the key issue is not simply legalisation, but commercialisation. Some warned that North America’s experience shows how legal cannabis can quickly become a major industry, with advertising and business incentives similar to those seen in tobacco and alcohol.
Others said the review provides important evidence for policymakers who want to reduce the harms of criminalisation without encouraging a large commercial market. The findings suggest that decriminalisation and strict regulation may not automatically increase use, while commercial sales may carry greater risks.
Why It Matters
The study matters because cannabis policy is changing rapidly around the world. Governments are trying to balance public health, criminal justice reform, and the realities of widespread cannabis use.
The review suggests that removing criminal penalties for possession may not be the same as creating a commercial cannabis industry. That distinction could shape future laws, especially in countries debating whether to legalise, decriminalise, or regulate cannabis more tightly.
What Comes Next
Policymakers are likely to pay close attention to the difference between decriminalisation and commercialisation. Future debates may focus less on whether cannabis should remain illegal and more on who controls supply, how strong products can be, and whether advertising should be restricted.
Researchers also say more long-term data is needed, especially because many cannabis reforms are still relatively recent compared with the long history of alcohol and tobacco regulation.
