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17 January 2025

Scientists show for the first time that risk of psychotic disorder appears to decline with time following cannabis use cessation

New research reports that cannabis users' risk of developing psychotic disorders appears to decrease with time once they stop using the drug.

smoking cannabis

New research from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London has reported that cannabis users' risk of developing psychotic disorders appears to decrease with time once they stop using the drug.

The research, published in the Canadian Journal of Psychiatry, found that it takes about 37 weeks of cannabis abstinence for a user’s risk of developing psychosis to recede to the same levels of those who had never used it. The researchers did however identify that frequent users of high potency strains might maintain an elevated risk, even over the course of 181 weeks.

There is extensive research suggesting that cannabis use is associated with an increased risk of the user developing psychosis, as well as poor mental health and sleep. Daily and high-potency users facing particularly increased risk.

Researchers on this study wanted to establish whether the risk of psychotic disorders in cannabis users changed over time after ceasing use. Using data sourced from the EU-GEI case-control study - a multi-centre study of first episode psychosis (FEP) patients and population controls across 11 areas in Europe and South America – scientists compared the experiences of 875 FEP patients against 1230 participants without psychosis.

Seven aspects of cannabis use were measured and analysed:

  1. Lifetime cannabis use
  2. Current cannabis use
  3. Age first tried cannabis
  4. Duration of cannabis use
  5. Frequency of cannabis use
  6. Potency of cannabis use
  7. Time since cessation in weeks

Researchers categorised users according to if and when they had given up cannabis and then assessed risk of psychosis for each group by analysing the likelihood of developing psychosis compared to those who had never used cannabis. Their analysis found that the risk of psychosis declines following the cessation of cannabis use with the risk being less for those who have ceased use for longer.

Ex-users who had only recently stopped (between one and four weeks) had nearly a seven-fold increase in the likelihood of developing psychosis compared to never-users, which suggests that stopping use of cannabis can precipitate psychosis in some as part of its withdrawal syndrome. After five to 12 weeks the risk for psychotic disorders dropped to a three-fold increase compared to those who had never used cannabis. In contrast to former users who had abstained for a minimum 37 weeks, there was no difference in risk of psychosis compared to those who had never used the drug.

“Our study, which is the first to examine whether the risk of a psychotic disorder goes down if a person ceases cannabis use, is vital. As the legalisation of cannabis continues to grow, so too will the number of people using the drug. Our study provides important evidence confirming that sustained cessation of cannabis use is associated with a decreased risk of psychosis.”

Dr Isabelle Austin-Zimmerman, a Research Associate at King’s IoPPN and the study’s joint senior author

Researchers did however establish that the declining risk was dependent on the nature of a person’s use.

Professor Marta Di Forti, Professor of Drug use, Genetics and Psychosis at King’s IoPPN and the study’s joint senior author, “Developing psychosis has the potential to have a drastically negative impact on a person’s day-to-day life, as well as their family. Our study established that daily users, and those who use higher potency strains, continued to remain at risk even after they stopped using cannabis at least within the timeframe assessed by our study. Our findings highlight the importance of offering support to people, particular regular users, who decide to stop using cannabis, because a sudden discontinuation in some could actually precipitate psychosis, possibly through an initial worsening of sleep and or anxiety, as other research has suggested. The next step is to replicate our findings using data from a longitudinal study as we are planning already”

 

Cannabis Use Cessation and the Risk of Psychotic Disorders: A Case-Control Analysis from the First Episode Case-Control EU-GEI WP2 Study (DOI.org/10.1177/07067437241290187) (Benjamin W Bond, Bea Duric, Edoardo Spinazzola, Giulia Trotta, Edward Chesney, Zhikun Li, Diego Quattrone, Giada Tripoli, Charlotte Gayer-Anderson, Victoria Rodriguez, Laura Ferraro, Caterina La Cascia, Ilaria Tarricone, Andrei Szöke, Celso Arango, Julio Bobes, Miquel Bernardo, Cristina Marta Del-Ben, Paulo Rossi Menezes, Jean-Paul Selten, Bart PF Rutten, Lieuwe de Haan, Simona Stilo, Franck Schürhoff, Baptiste Pignon, Tom P Freeman, Evangelos Vassos, Robin M Murray, Isabelle Austin-Zimmerman, Marta Di Forti) was published in the Canadian Journal of Psychiatry.

For more information, please contact Patrick O’Brien (Media Manager)  

In this story

Marta Di Forti

Professor of Drug use, Genetics and Psychosis

Robin Murray

Professor of Psychiatric Research

Research Assistant

Academic Clinical Lecturer

Research Associate

Evangelos Vassos

Senior Clinical Research Fellow