Does Cannabis Use Influence Schizophrenia? Study Sheds New Light

Since the legalization of cannabis in many regions, there have been many wondering whether there is a link between Cannabis Use Disorder (CUD) and Schizophrenia.  Recently, a Canadian study titled ‘Changes in Incident Schizophrenia Diagnoses Associated With Cannabis Use Disorder After Cannabis Legalization‘¹ was conducted that aimed to shed light on this question and any links between the two conditions.

Study Overview

The researchers looked at data from over 13.5 million individuals aged 14 to 65 without a prior history of schizophrenia, in what is known as a ‘population-based cohort study’.  The researchers broke the data down to three time periods: pre-legalization (2006-2015), medical cannabis liberalization (2015-2018), and nonmedical cannabis legalization (2018-2022).  From there, they looked at changes in the population-attributable risk fraction (PARF) for CUD associated with schizophrenia – essentially, this means looking at whether cannabis use is a risk factor that is resulting in a rise in schizophrenia rates.

Key Findings

So, what did the researchers find?  While the incidence of schizophrenia remained stable overall, it was revealed that the PARF for CUD associated with schizophrenia nearly tripled from 3.7% during the pre-legalization period to 10.3% post-legalization.  Notably, the PARF was highest among males aged 19 to 24 years (18.9%) and lowest among females aged 45 to 65 years (1.8%).

Simply put, this means that, based on the results, it is not believed that cannabis causes schizophrenia.  Rather, it suggests that cannabis use may exacerbate symptoms in individuals predisposed to or already suffering from schizophrenia.  Additionally, the increase in PARF coincides with not just rising cannabis use but higher THC content in cannabis products.  So, rather than being a direct cause, the increase could be due to changing trends in society.

Addressing Misconceptions

When looking at the results of the study, there are a few crucial considerations for those that either use, or are considering using cannabis.  Firstly, recognize that schizophrenia has both genetic and hereditary factors involved.  If you are a young adult male and believe yourself to be predisposed to the condition, it is most likely wise to refrain from consuming cannabis.

With the study shedding new light on the relationship between cannabis and schizophrenia, the following misconception can be more easily refuted.

Misconception: Cannabis use Inevitably Leads to Schizophrenia

While the study found an association between CUD and schizophrenia, it is important to remember that association does not equal causation.  Many factors contribute to schizophrenia, including genetic predisposition and environmental factors.  Cannabis use may exacerbate existing vulnerabilities or trigger symptoms in those already predisposed, but it is not the sole or direct cause of the disorder.

The Benefits of Cannabis

While it is important to acknowledge the potential risks associated with cannabis use, especially in vulnerable populations, it is equally important to recognize its benefits.  Cannabis has been proven to offer therapeutic relief for various conditions, including chronic pain, multiple sclerosis, and even nausea.  It has also shown great promise in treating anxiety, PTSD, and epilepsy, particularly in cases where traditional treatments have failed.

Aside from its medicinal benefits, cannabis legalization has also brought about significant societal benefits.  Namely, it has reduced the burden on the criminal justice system, generated substantial tax revenue through legal sales, and continues to create many jobs in what remains a burgeoning industry.

Conclusion

Overall, the study showed that while there is a clear association between CUD and schizophrenia, one does not cause the other.  Rather, individuals already suffering from or predisposed to schizophrenia may see their symptoms made worse.  While cannabis has many amazing benefits, studies like this are crucial for potential users to make an informed decision on consumption by having a more well-rounded perspective on potential risk factors.

Study Reference:

^{1. Myran, D. T., Pugliese, M., Harrison, L. D., et al. (2025). Changes in incident schizophrenia diagnoses associated with cannabis use disorder after cannabis legalization. JAMA Network Open, 8(2), e2457868. https://doi.org/10.1001/jamanetworkopen.2024.57868}