Summary: Researchers discovered shared genetic underpinnings for cannabis use and psychiatric disorders like schizophrenia and bipolar disorder. Employing advanced statistical modeling, the study revealed a complex interplay of genetic variants increasing or decreasing risk factors for these conditions.
These findings may contribute to personalized preventive measures and interventional strategies. Furthermore, improved understanding of this genetic overlap could aid in more specialized treatment plans.
Key facts:
- The study identifies shared genetic factors increasing the susceptibility to both cannabis use and certain psychiatric disorders.
- Some genetic variants can have opposing effects – increasing risk of cannabis use while decreasing the risk of schizophrenia or bipolar disorder.
- These findings can potentially revolutionize preventative measures, intervention strategies and the development of more targeted treatments.
Source: University of Oslo
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 modeling, 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.
About this genetics and mental health research news
Author: Press Office
Source: University of Oslo
Contact: Press Office – University of Oslo
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“The relationship between cannabis use, schizophrenia, and bipolar disorder: a genetically informed study” by Weiqiu Cheng et al. Lancet Psychiatry
Abstract
The relationship between cannabis use, schizophrenia, and bipolar disorder: a genetically informed study
Background
The relationship between psychotic disorders and cannabis use is heavily debated. Shared underlying genetic risk is one potential explanation. We investigated the genetic association between psychotic disorders (schizophrenia and bipolar disorder) and cannabis phenotypes (lifetime cannabis use and cannabis use disorder).
Methods
We used genome-wide association summary statistics from individuals with European ancestry from the Psychiatric Genomics Consortium, UK Biobank, and International Cannabis Consortium. We estimated heritability, polygenicity, and discoverability of each phenotype. We performed genome-wide and local genetic correlations. Shared loci were identified and mapped to genes, which were tested for functional enrichment. Shared genetic liabilities to psychotic disorders and cannabis phenotypes were explored using causal analyses and polygenic scores, using the Norwegian Thematically Organized Psychosis cohort.
Findings
Psychotic disorders were more heritable than cannabis phenotypes and more polygenic than cannabis use disorder. We observed positive genome-wide genetic correlations between psychotic disorders and cannabis phenotypes (range 0·22–0·35) with a mixture of positive and negative local genetic correlations. Three to 27 shared loci were identified for the psychotic disorder and cannabis phenotype pairs. Enrichment of mapped genes implicated neuronal and olfactory cells as well as drug–gene targets for nicotine, alcohol, and duloxetine.
Psychotic disorders showed a causal effect on cannabis phenotypes, and lifetime cannabis use had a causal effect on bipolar disorder. Of 2181 European participants from the Norwegian Thematically Organized Psychosis cohort applied in polygenic risk score analyses, 1060 (48·6%) were females and 1121 (51·4%) were males (mean age 33·1 years [SD 11·8]). 400 participants had bipolar disorder, 697 had schizophrenia, and 1044 were healthy controls.
Within this sample, polygenic scores for cannabis phenotypes predicted psychotic disorders independently and improved prediction beyond the polygenic score for the psychotic disorders.
Interpretation
A subgroup of individuals might have a high genetic risk of developing a psychotic disorder and using cannabis. This finding supports public health efforts to reduce cannabis use, particularly in individuals at high risk or patients with psychotic disorders. Identified shared loci and their functional implications could facilitate development of novel treatments.
Funding
US National Institutes of Health, the Research Council Norway, the South-East Regional Health Authority, Stiftelsen Kristian Gerhard Jebsen, EEA-RO-NO-2018–0535, European Union’s Horizon 2020 Research and Innovation Programme, the Marie Skłodowska-Curie Actions, and University of Oslo Life Science.
