A major international review of cannabis policies across the world has found that the commercialisation of cannabis, rather than its decriminalisation, is associated with increased consumption, higher drug potency and a rise in mental health problems, including psychosis. The findings are expected to influence ongoing policy debates in several countries considering reforms to cannabis laws.
The review, examined cannabis policy changes implemented between 2000 and 2025 and assessed their impact on usage patterns, addiction rates, drug potency and psychiatric disorders. Researchers analysed evidence from countries and regions that adopted varying approaches ranging from decriminalisation and strict state regulation to fully commercial legal markets.
According to the study, jurisdictions that allowed commercial cannabis markets, particularly in parts of the United States and Canada, witnessed a notable increase in the number of users and the strength of cannabis products available. Researchers also recorded a rise in hospital admissions linked to psychosis and other cannabis-related mental health conditions in these areas.
In contrast, countries and regions that decriminalised cannabis possession without creating a profit-driven retail industry showed little evidence of increased use or worsening psychiatric outcomes. Similar trends were observed in Uruguay, the first country to legalise cannabis nationally while maintaining strict state oversight of production and distribution. Researchers found that Uruguay’s tightly controlled model did not produce the same surge in consumption or mental health concerns seen in more commercialised systems.
Lead researcher Professor Tom Freeman of the University of Bath said the findings suggest policymakers should distinguish between decriminalisation and commercial legalisation when considering reforms. He noted that profit-driven industries often have strong incentives to market stronger and cheaper products in order to increase sales, potentially leading to greater public health harms. The study draws parallels with the historical experiences of the tobacco and alcohol industries, where commercial interests have frequently complicated public health regulation.
Mental health experts welcomed the review, describing it as one of the most comprehensive assessments of cannabis policy outcomes to date. Professor Sir Robin Murray of King’s College London said evidence increasingly points to commercialisation, rather than legalisation itself, as the key factor behind rising harms. He warned that aggressive marketing and expanding industry influence could contribute to greater consumption and associated health risks.
The findings come amid ongoing discussions in several countries, including the United Kingdom, about reforming cannabis laws. Advocates of decriminalisation argue that criminal penalties disproportionately affect marginalised communities while doing little to reduce drug use. The review suggests that carefully regulated or decriminalised models may not lead to the sharp increases in usage often predicted by opponents of reform.
Researchers stressed that global cannabis policies are still relatively new and require continued monitoring. However, the review concludes that governments considering reforms should pay close attention to the structure of cannabis markets, as public health outcomes appear to depend less on whether cannabis is legal and more on how its production and sale are regulated.
