High-THC cannabis is linked to higher psychosis risk.

Young, heavy users face the greatest mental health danger.

Legalization may require stricter potency controls.

Suddenly, warnings about cannabis are everywhere. In early February, Canadian researchers reported that rates of severe mental illness among young people have risen alongside increased access to high-potency cannabis (Callaghan, et al., 2022). Around the same time, a new book, A Killing in Cannabis (Kohn, 2024), revisited a 2019 California murder and highlighted how violence tied to the marijuana trade has persisted even after legalization. On February 9, 2024, an opinion piece from the New York Times editorial board called for new regulations around high-THC cannabis products, asserting the U.S. has an increasing marijuana problem and acknowledging the growing concern over marijuana addiction and psychosis. Many have dismissed these warnings as simply fear-mongering. But now you read these same types of articles published in more traditional outlets. What's different?

The Rise of High-Potency Cannabis

Cannabis has seen significant changes in terms of potency over the last two decades. The average level of THC in cannabis has increased greatly since the 1990s (ElSohly et al., 2016). Highly concentrated THC extracts sold in legal markets, such as vape cartridges, can be found at near-pure levels. Such products are growing in popularity because they are discreet and relatively easy to manufacture. Research suggests that the level of potency in cannabis impacts the likelihood of developing psychotic disorders. A large multi-site study of daily high-potency cannabis consumers across Europe indicated that there was a correlation between the use of high-potency cannabis and increased odds of developing psychotic disorders (Di Forti et al., 2019).

A longitudinal study in The Lancet Psychiatry reported that adolescents who used cannabis had an increased risk of experiencing psychotic symptoms later in life (Murray et al., 2017). There is a plausible biological mechanism that helps to explain these potential outcomes. THC impacts the dopamine circuit of the brain, which is involved in the development of psychosis and Schizophrenia (Volkow et al., 2014). The THC-induced effects of cannabis are usually temporary for most users; however, heavy use of cannabis on a regular basis can precipitate the onset of psychiatric disorders among young, at-risk individuals with genetic or environmental vulnerability. It is important to note that not all young people who use cannabis will develop schizophrenia; however, the risk is real and cannot be dismissed.

Personal Stories and Public Awareness

Statistical evidence is vital, however, when paired with compelling testimony, it appears even more credible due to human experience and emotion. Recently, public figures have shared their own experiences regarding cannabis usage contributing to mental illness and devastation in their family. These public testimonies have gained traction across many demographics. Many families, including parents, siblings, and friends, have similarly witnessed this issue unfold quietly within their own households. Schizophrenia is chronic and disabling, often involving symptoms such as hallucinations, delusions, and paranoia. As such, individuals who live with schizophrenia frequently endure the disruption of their education, instability of employment, and isolation from society. Although antipsychotic medications are available to treat these individuals, they also have serious and detrimental side effects. In addition, mental illness impacts more than just the individual; it impacts the entire family.

Epidemiological research supports that the use of cannabis is associated with psychosis at the population level. A systematic review and meta-analysis of epidemiological data established that cannabis usage substantially increased the risk of psychotic outcomes (e.g., schizophrenia) across all users; however, frequent cannabis users are at an even greater risk (Marconi et al., 2016). Additionally, there is a dose-dependent risk associated with cannabis use for psychotic outcomes; therefore, frequent users of more potent cannabis products are at an even higher risk for developing adverse outcomes than infrequent users of less potent products. For many years now, these findings have remained uncomfortable together, partially due to the shifting culture of cannabis towards normalcy and commercialization.

Legalization, Commercialization, and Messaging

Over the last several years, public opinion has been moving towards the support of legalizing cannabis. Many American citizens perceive cannabis to be less harmful than alcohol or opioids. The narrative surrounding legalization has been framed as an issue of personal liberty, criminal justice reform, and economic opportunity. Yet, with legalization comes the commercialization of cannabis. Retail outlets are stocking brightly packaged products that come in a variety of formats (edibles, vapes, concentrates) that have high levels of THC.

Advertising for these products often creates confusion about whether the use of cannabis is for medical or recreational purposes. The promise that cannabis helps reduce anxiety or depression can be attractive to younger populations, particularly those who are already experiencing negative mental health issues. However, the evidence supporting the use of cannabis for the treatment of psychiatric disorders is limited and mixed. For example, while some individuals may attempt to use cannabis to cope with the symptoms of chronic stress or trauma, over time, the use of cannabis may exacerbate the symptoms of chronic stress or trauma (Volkow et al., 2014). Additionally, self-medication with cannabis may mask underlying mental health issues and increase the risk of cannabis dependence.

Since the legalization of cannabis, there has been an increase in emergency department visits related to cannabis consumption and use in some states (Hall & Lynskey, 2020). While correlation does not imply causation, the increase in emergency department visits has raised concerns amongst both clinicians and public health professionals. Legalization by itself does not appear to be the sole issue; rather, the process by which legalization occurred – spur-of-the-moment expansion, increased potency, and lack of adequate public education regarding the risks of cannabis consumption – may also be problematic.

Media Narratives and Cultural Shifts

The cannabis controversy is one of polarized views. Legalization opponents have been labeled as exaggerating or suffering from moral panic, while those who support legalization have either highlighted racial disparities in drug law enforcement or pointed to prohibition's social costs. The two groups have valid points. In the past, excess criminal punishment was inflicted on minority populations through drug laws, but there is now a growing body of research to suggest that high-potency cannabis might be associated with psychiatric illness. We also see how some cultural narratives can oversimplify complex realities.

When cannabis is framed as being completely harmless, or as a panacea for everything, people struggle to develop an accurate understanding of the drug or how to assess risk, especially for youth. Studies have shown that young people often downplay their own risk of cannabis use if they think the drug being legal means it is safe. Editorials and research on this topic have also shown some evidence of a shifting public view about these issues; therefore, simply recognizing that some psychiatric issues may result from cannabis use does not mean we have to revert back to blanket prohibitive drug law status; however, part of this new frame may involve instituting THC potency limits, adding product labelling requirements, placing age restrictions on cannabis retail purchases, and providing honest messaging about potential health risks of using cannabis.

In many places, the general public still supports cannabis legalization, though most adults who support legalization do not typically use cannabis regularly themselves. Many consumers may also be unaware of how much stronger cannabis products are now compared to past products or how cannabis concentrates present a higher risk to heavy, early-onset users. If attitudes toward cannabis are shifting positively, it may be because of the visible negative impact of cannabis on people's lives (families dealing with psychosis, addiction, academic failure, etc.), clinicians seeing patterns of behavior in patients that cannot be overlooked, and researchers developing evidence that contradicts previous optimism regarding cannabis. Responses may include more regulation of THC-concentrated cannabis products, increased funding for mental health treatment services, or prevention campaigns aimed at adolescent populations.

The legislation does not have to be punitive. It can be viewed as an opportunity for clarification. Cannabis is not a harmless herb, and it is not an especially bad thing. However, like alcohol, cannabis poses different risks based on dosage, age of use, and an individual's susceptibility. What differs about today's cannabis is that it is much more potent than was available in previous generations, and the speed at which cannabis has been commercialized has outpaced society's understanding of cannabis.

Trends come and go, as do the late-breaking news events that generate huge amounts of media attention. With a few billion dollars at stake in many different industries, there will be consequences to losing. However, the nature of the conversation has changed from mental health issues being marginalized to being included as part of the general discussion. The debate between personal liberty and the honest recognition of risk, particularly for young people who have not fully matured, is what parents, educators, and policymakers will begin to focus upon, and this will determine how cannabis is treated going forward. What follows will depend on what we're willing to face.

Callaghan, R. C., Sanches, M., Murray, R. M., Konefal, S., Maloney-Hall, B., & Kish, S. J. (2022). Associations between Canada's cannabis legalization and emergency department presentations for transient cannabis-induced psychosis and schizophrenia conditions: Ontario and Alberta, 2015–2019. Canadian Journal of Psychiatry, 67(8), 616–625. doi: 10.1177/07067437211070650.

ElSohly, M. A., Mehmedic, Z., Foster, S., et al. (2016). Changes in cannabis potency over the last two decades (1995–2014). Biological Psychiatry, 79(7), 613–619. https://doi.org/10.1016/j.biopsych.2016.01.004

Forti, M., Quattrone, D., Freeman, T. P., et al. (2019). The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe. The Lancet Psychiatry, 6(5), 427–436. https://doi.org/10.1016/S2215-0366(19)30048-3

Hall, W., & Lynskey, M. (2020). Assessing the public health impacts of legalizing recreational cannabis use. Addiction, 115(3), 575–577. doi: 10.1002/wps.20735

Kohn, D. (2024). A Killing in Cannabis: The Untold Story of a California Murder and the Violent World of Legal Weed. New York, NY: Crown.

Marconi, A., Di Forti, M., Lewis, C. M., et al. (2016). Meta-analysis of the association between the level of cannabis use and risk of psychosis. Schizophrenia Bulletin, 42(5), 1262–1269. https://doi.org/10.1093/schbul/sbw003

Murray, R. M., Englund, A., Abi-Dargham, A., et al. (2017). Cannabis-associated psychosis: Neural substrate and clinical impact. The Lancet Psychiatry, 4(12), 991–1001. doi: 10.1016/j.neuropharm.2017.06.018.

The New York Times Editorial Board. (2024, February 9). The U.S. Has a Marijuana Problem. The New York Times. https://www.nytimes.com/2026/02/10/opinion/legalized-marijuana-laws-reg…

Volkow, N. D., Baler, R. D., Compton, W. M., et al. (2014). Adverse health effects of marijuana use. The New England Journal of Medicine, 370(23), 2219–2227. https://doi.org/10.1056/NEJMra1402309

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