In a large European case-control study, the elevated psychosis risk associated with cannabis use declined after quitting and returned to never-user levels after approximately 37 weeks of abstinence, though heavy users of high-potency cannabis may retain elevated risk longer.
Psychiatrists, people considering quitting cannabis, addiction counselors, policy researchers
Psychosis risk returned to never-user levels after approximately 37 weeks of cannabis abstinence
What the researchers found
Ex-users who stopped 1-4 weeks prior had 6.9 times the psychosis odds of never-users. This declined progressively: those who stopped 37-96 weeks prior had no significant elevation (OR 1.01). However, preliminary results suggested frequent users of high-potency cannabis might maintain elevated risk even beyond 181 weeks of abstinence.
Why it matters
This is the first large multi-site study to quantify how quickly psychosis risk declines after stopping cannabis. The finding that risk returns to baseline after about 9 months offers concrete information for people considering quitting, while the caveat about high-potency use adds important nuance.
The numbers in context
Ex-users stopped 1-4 weeks: OR 6.89; stopped 37-96 weeks: OR 1.01 (not significant); stopped 97-180 weeks: OR 0.73 (not significant); stopped 181+ weeks: OR 1.18 (not significant); frequent high-potency users may retain elevated risk beyond 181 weeks; data from multiple European sites and Brazil
How the study worked
Case-control study from the EU-GEI network collecting data from first-episode psychosis patients and population controls across sites in Europe and Brazil (May 2010 to April 2015). Adjusted logistic regression examined how psychosis odds changed with time since cannabis cessation.
What this study cannot tell us
Case-control design cannot prove causation, relies on retrospective self-report of cannabis use timing, the high-potency finding is preliminary with wide confidence intervals, may not generalize to all populations, does not account for all potential confounders
How to read the evidence
Large multi-site case-control study across Europe and Brazil with adjusted analyses; strong design but retrospective self-report of cessation timing
When this study was published
Published 2025
The bigger picture
The reversibility of cannabis-associated psychosis risk has been a critical unanswered question. This study suggests that for most users, the elevated risk is not permanent, which could motivate cessation efforts. The exception for high-potency users aligns with growing concerns about modern cannabis products.
Questions still open
- Is the 37-week threshold consistent across different genetic risk profiles? Does the persistent risk for high-potency users reflect permanent brain changes? Would similar results appear in non-European populations?
Common questions
How long does it take for psychosis risk to normalize after quitting cannabis?
Does the type of cannabis matter for psychosis risk after quitting?
Read the original research
Cannabis Use Cessation and the Risk of Psychotic Disorders: A Case-Control Analysis from the First Episode Case-Control EU-GEI WP2 Study: L'arrêt de l'utilisation du cannabis et le risque de troubles psychotiques: Une analyse cas-témoins tirée de l'étude cas-témoins EU-GEI WP2 centrée sur les premiers épisodes psychotiques.
Canadian journal of psychiatry. Revue canadienne de psychiatrie, 70(3), 182-193
Citation
Bond, Benjamin W; Duric, Bea; Spinazzola, Edoardo; Trotta, Giulia; Chesney, Edward; Li, Zhikun; Quattrone, Diego; Tripoli, Giada; Gayer-Anderson, Charlotte; Rodriguez, Victoria; Ferraro, Laura; La Cascia, Caterina; Tarricone, Ilaria; Szöke, Andrei; Arango, Celso; Bobes, Julio; Bernardo, Miquel; Del-Ben, Cristina Marta; Menezes, Paulo Rossi; Selten, Jean-Paul; Rutten, Bart P F; de Haan, Lieuwe; Stilo, Simona; Schürhoff, Franck; Pignon, Baptiste; Freeman, Tom P; Vassos, Evangelos; Murray, Robin M; Austin-Zimmerman, Isabelle; Di Forti, Marta. (2025). Cannabis Use Cessation and the Risk of Psychotic Disorders: A Case-Control Analysis from the First Episode Case-Control EU-GEI WP2 Study: L'arrêt de l'utilisation du cannabis et le risque de troubles psychotiques: Une analyse cas-témoins tirée de l'étude cas-témoins EU-GEI WP2 centrée sur les premiers épisodes psychotiques.. Canadian journal of psychiatry. Revue canadienne de psychiatrie, 70(3), 182-193. https://doi.org/10.1177/07067437241290187
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