A new study from the University of Oslo published in the Lancet Psychiatry, reported a shared genetic basis for cannabis use and psychiatric disorders, including schizophrenia and bipolar disorder. These findings may indicate that a subset of the population is at high risk for both cannabis use and psychiatric disorders, based on their genetic propensity.

There has been much debate over the relationship between cannabis use and psychiatric disorders. Cannabis is a psychoactive drug which sometimes produces psychotic-like symptoms. Additionally, the rate of cannabis use is high among patients with disorders linked to psychosis, such as schizophrenia and bipolar disorder.

Genetic factors play an important role in determining an individual’s susceptibility to developing psychiatric disorders or their likelihood of using cannabis. Some of the genetic variants associated with cannabis use are also linked to psychiatric disorders.

This recent study, led by Drs. Weiqiu Cheng and Nadine Parker, provides evidence that shared genetic factors underlie this relationship. “This study shows that there is a shared genetic basis underlying our susceptibility to both cannabis use and certain psychiatric disorders. These findings may indicate that a subset of the population is at high risk for both cannabis use and psychiatric disorders, based on their genetic propensity”, lead author Weiqiu Cheng says.

Using advanced statistical modelling, the study shows that the majority of shared variants increase the risk of both cannabis use and developing either schizophrenia or bipolar disorder. Still, there are some genetic variants with opposing effects, that increase the risk of cannabis use while decrease the risk of the two psychiatric disorders, suggesting a complex relationship.

“These findings are important as they show that the complex links between cannabis use and these disorders may not only be caused by cannabis use itself, but could also be driven by shared genetic susceptibility”, researcher Nadine Parker says.

Cannabis is used medicinally for relief of pain and as an antidepressant in some regions of the world. Also, one component of cannabis is being considered as a potential treatment for psychosis. “Shared genetic variants with opposing effects may suggest the presence of biological mechanisms that could support the beneficial effects of cannabis”, the researchers point out.

These new findings have several important clinical implications. Firstly, this information may result in personalized care including preventative and interventional measures for high-risk individuals. This may include reducing cannabis use among individuals at high genetic risk for schizophrenia and bipolar disorder. Secondly, future studies investigating the biological effects of the shared genetic variants may contribute to the development of more targeted treatment efforts. Finally, the improved knowledge about genetic overlap can be used to help stratify patients for more specialized treatment plans.

Full bibliographic information

Published on 19/05/2023 by University of Oslo, Faculty of Medicine
Authors: Weiqiu Cheng*, Nadine Parker*, Naz Karadag, Elise Koch, Guy Hindley, Romain Icick, Alexey Shadrin, Kevin S O’Connell, Thomas Bjella, Shahram Bahrami, Zillur Rahman, Markos Tesfaye, Piotr Jaholkowski, Linn Rødevand, Børge Holen, Trine Vik Lagerberg, Nils Eiel Steen, Srdjan Djurovic, Anders M Dale, Oleksandr Frei, Olav B Smeland, Ole A Andreassen.
Title: The relationship between cannabis use, schizophrenia, and bipolar disorder: a genetically informed study. Lancet Psychiatry. Epub 2023 May 17.