A study published in The Lancet Psychiatry has examined how different models of cannabis regulation affect consumption patterns, dependence, and mental health outcomes. The research was conducted by an international team led by scientists from University of Bath.

The researchers analyzed cannabis policy changes across multiple countries between 2000 and 2025, ranging from full criminalization to commercial legalization. Their conclusions were nuanced: decriminalization and tightly regulated legalization generally do not appear to cause a substantial increase in cannabis use. However, commercially driven legal markets show a markedly different pattern.

In countries with strictly controlled systems—where access is limited through pharmacies, cannabis clubs, or home cultivation, as in Uruguay—overall consumption levels have remained relatively stable. According to the review, these regulatory models have not been associated with significant increases in cannabis use.

A different picture emerges in jurisdictions where cannabis is legalized as a commercial product within an open market, including parts of the United States and Canada. In these settings, researchers observed increases in overall consumption, a growing proportion of daily users, and higher concentrations of psychoactive compounds in cannabis products.

The authors argue that commercialization itself is a key driver of risk. When a profit-oriented industry develops, companies are incentivized to expand product offerings, increase marketing efforts, and improve accessibility. These factors are associated with higher rates of cannabis dependence and increased demand for healthcare services, including treatment for cannabis-related psychotic episodes.

The study also reviewed the medical use of cannabinoids. Despite growing interest in their potential role in treating psychiatric conditions, the evidence remains limited. Across 54 studies, researchers found only moderate benefits for sleep disturbances, withdrawal symptoms, and certain neurological disorders. By contrast, convincing evidence of effectiveness was lacking for anxiety disorders, Post-Traumatic Stress Disorder, and Depression.

The review further notes that daily cannabis use may increase the risk of psychotic disorders, particularly among individuals with existing vulnerabilities or other risk factors. However, the relationship between cannabis use and conditions such as depression and anxiety remains less certain and continues to be debated.

The authors conclude that different regulatory approaches can produce fundamentally different public health outcomes. While decriminalization and carefully regulated legalization do not appear to substantially increase cannabis use, commercialization of the market is associated with higher consumption rates and a greater burden of adverse health consequences, particularly those affecting mental health.