The link between cannabis and its effects on mental health, particularly schizophrenia, continues to spark debate. While many tout marijuana’s calming effects, particularly in online forums, mental health experts caution against its use—especially among young people. Research increasingly reveals a concerning relationship between cannabis use and psychotic disorders like schizophrenia.
More Than Just a High: The Cannabis-Schizophrenia Link
Beyond the “high” associated with marijuana, many users report paranoia or hallucinations while under the influence. This is due to the active component, Tetrahydrocannabinol (THC). THC binds to receptors in the brain and triggers a series of reactions in brain cells. Typically, these effects fade after the high wears off, but in some cases, they may last longer, leading to what’s known as cannabis-induced psychosis.
In high-risk individuals, cannabis can disrupt brain development and lead to conditions like schizophrenia—a severe mental illness characterized by long-term hallucinations, delusions, and paranoia. A Finnish study of 18,000 individuals with cannabis-induced psychosis found that nearly 50% were later diagnosed with schizophrenia (1). Other studies confirm that regular use, especially of high-potency products, increases the risk of developing schizophrenia by four times (2). This risk is comparable to the relationship between high cholesterol and heart disease.
The Specialized Treatment Early in Psychosis (STEP) program at Yale found that over 75% of patients with early schizophrenia had a history of cannabis use, further cementing this link (3).
Myth vs. Fact: Cannabis as a Remedy for Psychosis?
Myth: Some believe that cannabis can ease the distress of psychotic symptoms, a theory known as the “self-medication hypothesis.” This stems from reports of temporary calm after using marijuana.
The fact: Cannabis contains both THC and Cannabidiol (CBD), the latter known for its calming effects. However, it’s impossible to consume CBD without THC when using natural cannabis.
The plot twist: In individuals with schizophrenia, the initial calm from smoking marijuana may quickly give way to a worsening of psychotic symptoms like paranoia and hallucinations (4). Research shows no evidence that it alleviates schizophrenia symptoms; in fact, regular cannabis use worsens outcomes for those with schizophrenia or other psychotic disorders (5,6).
Who is at risk? What can we do?
The biggest risk factor for cannabis-induced psychosis and schizophrenia is a family history of schizophrenia, suggesting a genetic predisposition. For those with a family member diagnosed with schizophrenia, using cannabis is a high-risk gamble. Even without a family history, waiting until age 25 before using is recommended, as brain development continues into young adulthood (7,8).
The risk is also greater with high-potency cannabis strains, making it crucial for users to buy from dispensaries that clearly document THC levels below 15% (2). Regular use of higher-potency strains significantly increases the likelihood of developing psychosis.
Conclusion: Understanding the Risks
While cannabis may offer temporary benefits, the long-term dangers—especially the risk of psychosis—should not be ignored. It’s vital for young people to fully understand the potential mental health risks.
Learn More
We encourage you to join us at our Provider Trainings and Family & Community Workshops hosted by the STEP Learning Collaborative.
In a recent workshop, Dr. Deepak Cyril D’Souza, Professor of Psychiatry at Yale School of Medicine and Director of the Yale Center for the Science of Cannabis and Cannabinoids, discusses cannabis’s impact on psychosis. You can watch his full presentation here.
Be in the Know: Visit beintheknowct.org to learn about Connecticut laws, how marijuana affects mental and physical health, and signs of problem use.
References
- Niemi-Pynttäri, J. A. et al. Substance-induced psychoses converting into schizophrenia: a register-based study of 18,478 Finnish inpatient cases. J. Clin. Psychiatry 74, e94–9 (2013).
- Di Forti, M. et al. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study. The Lancet Psychiatry 6, 427–436 (2019).
- Kline, E. R. et al. Timing of cannabis exposure relative to prodrome and psychosis onset in a community-based first episode psychosis sample. J. Psychiatr. Res. 147, 248–253 (2022).
- Henquet, C. et al. Psychosis reactivity to cannabis use in daily life: an experience sampling study. Br. J. Psychiatry 196, 447–453 (2010).
- Levi, L. et al. Cannabis Use and Symptomatic Relapse in First Episode Schizophrenia: Trigger or Consequence? Data From the OPTIMISE Study. Schizophr. Bull. 49, 903–913 (2023).
- Schoeler, T. et al. Poor medication adherence and risk of relapse associated with continued cannabis use in patients with first-episode psychosis: a prospective analysis. LancetPsychiatry 4, 627–633 (2017).
- Keshavan, M., Lizano, P. & Prasad, K. The synaptic pruning hypothesis of schizophrenia: promises and challenges. World Psychiatry 19, 110–111 (2020).
- Petanjek, Z. et al. Extraordinary neoteny of synaptic spines in the human prefrontal cortex. Proc. Natl. Acad. Sci. U. S. A. 108, 13281–13286 (2011).