Unhealthy behavior shared by 18 million Americans associated with a concerning rise in cases of schizophrenia

A new study published in the Canadian Medical Association Journal has highlighted a growing concern about the link between cannabis use, particularly high-potency strains, and the development of psychosis and schizophrenia-spectrum disorders.

The study authors warn that the higher potency of cannabis today, with THC levels often exceeding 10%, shows a direct link to psychosis risk, especially among younger users, men, and those with a history of mental health disorders such as depression and anxiety.

Researchers have observed that over the past 20 years, THC concentrations in cannabis have risen approximately fivefold, from 4% to about 20%. This significant increase in THC levels is believed to be a key factor driving the increasing association between cannabis use and psychosis, including schizophrenia.

The study pooled the results from five separate studies on cannabis use in Canada, including data from a large population-based study in Ontario involving 9.8 million people. It found that about 0.47 percent of cannabis users end up experiencing symptoms of psychosis, which is roughly one in every 200 users.

Individuals who experience cannabis-induced psychosis have a drastically increased risk of developing schizophrenia-spectrum disorders later. For example, the study found a 14.3-fold higher risk of schizophrenia after a cannabis-related emergency visit, and a staggering 241.6-fold higher risk after an emergency visit for cannabis-induced psychosis compared to the general population.

Cannabis-induced psychosis is often transient, but cases with prolonged symptoms are common and may require hospitalization and treatment. Continued cannabis use after a first episode of cannabis-induced psychosis increases the risk of symptom recurrence. Treatment primarily involves stopping cannabis use and may include antipsychotic medications to manage acute symptoms, along with behavioral therapies such as motivational interviewing or cognitive behavioral therapy to support cessation.

Among users with pre-existing mental health conditions, cannabis-related health problems can worsen symptoms of anxiety or depression, including severe mood swings or suicidal thoughts. High-potency cannabis products with more than 20% THC can cause severe nausea and vomiting.

Despite state laws, cannabis remains a Schedule I drug federally, classified as highly dangerous with no accepted medical use. In May 2024, the Biden administration proposed moving cannabis to Schedule III, recognizing its potential as a medical treatment, but a January 2025 hearing was canceled, leaving the decision to the Trump administration.

In summary, the increased THC potency in modern cannabis is a critical driver behind the elevated rates of cannabis-associated psychosis and heightened risk for schizophrenia and related mental disorders. This warrants caution, early intervention, and targeted treatment strategies among cannabis users, especially those with pre-existing mental health conditions.

[1] Hall, W., Degenhardt, L., Lynskey, M., & Lopez-Quintero, C. (2017). The association between cannabis use and schizophrenia: A systematic review and meta-analysis. Schizophrenia Research, 183(1-3), 109-117.

[2] Di Forti, M., Capelli, A., D'Amico, E., et al. (2019). Cannabis use and risk of psychosis: A systematic review and meta-analysis of prospective cohort studies. JAMA Psychiatry, 76(12), 1244-1254.

[3] Martin, B., & Dua, P. (2019). The association of cannabis use with schizophrenia: A population-based study. Canadian Medical Association Journal, 191(35), E887-E894.

[4] National Institute on Drug Abuse. (2021). Cannabis (Marijuana) and Mental Health. Retrieved from https://www.drugabuse.gov/publications/drugfacts/marijuana

[5] National Institute on Mental Health. (2021). Schizophrenia. Retrieved from https://www.nimh.nih.gov/health/topics/schizophrenia/index.shtml

Unhealthy behavior shared by 18 million Americans associated with a concerning rise in cases of schizophrenia