Drug legalization is supposed to spur several critical improvements in public health. As more states legalize recreational marijuana, we’re beginning to see how substantial these benefits are—and the results are underwhelming. A just-published review in The Lancet Psychiatry examining how cannabis policy changes from 2000 to 2025 relate to drug use, addiction and other psychiatric disorders paints a more complicated picture than many legalization advocates have described.
Commercialized legal cannabis markets in Canada and the US were linked to increased cannabis use and addiction among adults. “Since the mid-1990s and especially after 2015,” the review noted, “there has been an increase in the number of people using cannabis daily or near daily in the USA, who now exceed the number of people using alcohol daily or near daily.”
This increase in use has been accompanied by rises in drug potency as cannabis flower is increasingly “displaced by higher potency products that are associated with an increased risk of cannabis use disorder and psychotic disorder.” This is a striking result since legalization is generally thought to produce more predictable, safer drug supplies with fewer harmful effects as sellers begin to operate within the bounds of the law.
These markets also saw increases in hospital admissions for psychosis and for psychotic disorders occurring together with cannabis use disorder. However, there was no consistent evidence of changes in the overall prevalence or incidence of psychotic disorders at the population level. It’s also not clear if marijuana use causes psychosis or if people with psychotic disorders are more inclined to use the drug. Another more perplexing possibility is that cannabis use is both a cause and a result of psychosis in different cases.
In other parts of the world, the results varied with the scale of the changes to drug policy. In Europe, for instance, there was little connection between changes in cannabis regulation and drug use—”This is consistent with the small scale of policy change or commercialization in Europe when compared with the USA or Canada.”
The takeaway for now seems to be that markers of commercialization—retail density, lower prices, higher-potency products, and marketing—track with higher consumption and certain harms. Jurisdictions that restricted commercial influence through tight state controls or non-profit models showed weaker or no such associations. Long-term data remain limited, particularly from low- and middle-income countries, and most studies cover relatively short periods after policy changes.
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Join Dr. Liza Lockwood and Cam English on this episode of Facts & Fallacies as they scrutinize the results (so far) of marijuana legalization.
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Dr. Liza Lockwood is a medical toxicologist and the medical affairs lead at Bayer Crop Science. Follow her on X @DrLizaMD
Cameron J. English is the executive vice president at the American Council on Science and Health. Follow him on X @camjenglish
