A major study has found that countries where cannabis is sold commercially have seen a significant increase in users and rates of psychosis, raising concerns about the impact of profit-driven markets on public health. The research, published in Lancet Psychiatry, reviewed data from over two decades, showing that commercialisation leads to higher usage and more potent products, which can exacerbate mental health issues.
The study, led by Professor Tom Freeman at the University of Bath, examined policy changes across 25 countries between 2000 and 2025. It compared regions with commercial cannabis markets – such as parts of the US and Canada – to those where possession was decriminalised or tightly regulated. The results showed that in areas with commercial markets, user numbers rose by 10% on average, while hospital admissions for psychosis increased by 15%. In contrast, countries where possession was decriminalised saw little change in cannabis use or mental health outcomes.
The researchers found that the profit motive can drive companies to sell cheaper, high-potency products, which increases the risk of addiction and psychosis. This has echoes of the struggles to regulate industries like tobacco and alcohol, where increased sales have often correlated with greater harm to consumers. Professor Freeman notes that policymakers should consider decriminalisation or strict regulation over commercial markets.
In the UK, cannabis remains a Class B drug, with possession carrying penalties including up to five years in prison. A report by the London Drugs Commission last year advocated for decriminalising possession, highlighting racial disparities in policing and suggesting that current sanctions are disproportionate. Professor Sir Robin Murray from King's College London cautions that while more research is needed, there is a growing consensus that commercialisation of supply, rather than simply legalising recreational use, poses significant risks to public health.
The study's findings have implications for policymakers considering changes to cannabis laws. As the debate around decriminalisation and regulation continues in the UK, it is essential to consider the evidence from countries with different approaches to cannabis policy. By understanding the impact of commercial markets on public health, we can make informed decisions about how to mitigate risks and protect vulnerable populations.