Cannabis Use and Schizophrenia: Untangling the Genetic Threads
New research reveals a concerning link between frequent cannabis use and psychosis risk, highlighting the independent influence of both cannabis and genetics.
The study, published in Psychological Medicine, delved into the complex relationship between cannabis use, individual genetic predisposition to schizophrenia, and the likelihood of developing psychosis.
Researchers analyzed data from two large-scale studies – the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (EU-GEI) and the UK Biobank – encompassing over 150,000 participants.
Polygenic risk scores (PRSs) were calculated for both schizophrenia and cannabis use disorder, providing a way to assess the combined effect of multiple genetic variants associated with these conditions.
The findings were striking: Frequent cannabis use, particularly daily use of high-potency cannabis (defined as containing 10% or more delta-9 tetrahydrocannabinol), significantly increased the risk of psychosis, regardless of an individual’s schizophrenia PRS.
This suggests that cannabis and genetic susceptibility to schizophrenia contribute to psychosis risk through distinct pathways.
"Our study is the first to estimate the risk of psychosis from both cannabis use and genetic predisposition to schizophrenia," explained Dr Edoardo Spinazzola, lead author from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London. " Interestingly, we found no evidence of an interaction between the two, suggesting they influence the risk of psychosis through separate pathways and could potentially have an additive effect."
Further analysis revealed the highest risk for psychosis was observed in individuals with a greater genetic predisposition to schizophrenia who also used high-potency cannabis daily.
The study also investigated whether genetic vulnerability to schizophrenia influenced cannabis use patterns. Surprisingly, schizophrenia PRS was not associated with an individual’s likelihood to try cannabis or the frequency of use in those diagnosed with psychosis. However, among individuals without a psychosis diagnosis in the UK Biobank, the schizophrenia PRS was linked to lifetime and daily cannabis use, though this association weakened when the PRS for cannabis use disorder was factored in.
These findings hold significant implications at a time when global cannabis use and potency are on the rise. They highlight the urgent need for targeted preventative strategies, especially for individuals who are genetically vulnerable to schizophrenia.
"Daily users of high potency cannabis are at increased risk of developing psychosis independently from their polygenic risk score for schizophrenia," emphasized Professor Marta di Forti, co-author from the IoPPN.
"Nevertheless, the polygenic risk score for schizophrenia might, in the near future, become useful to identify those at risk for psychosis among less frequent users, enabling us to put preventative measures in place."
This research represents a valuable step forward in unraveling the intricate interplay between genetics, cannabis use, and psychosis. As the focus on personalized medicine grows, identifying and understanding individual risk factors will be crucial for developing effective prevention and treatment strategies.
How does the use of polygenic risk scores help researchers understand the relationship between cannabis use, genetics, and psychosis?
## Cannabis Use and Psychosis: A Genetic Puzzle
**Host:** Welcome back to the show. Today we’re diving into some fascinating new research on the complex relationship between cannabis, genetics, and psychosis. We’re joined by Dr. Emma Chen, a leading neuroscientist specializing in substance use and mental health. Dr. Chen, thanks for being here.
**Dr. Chen:** Thanks for having me!
**Host:** This new study is revealing some concerning links, isn’t it?
**Dr. Chen:** Absolutely. This research, published in *Psychological Medicine*, looked at data from over 150,000 participants across Europe and the UK. What they found was that frequent cannabis use, especially daily use of high-potency cannabis, significantly increased the risk of psychosis, regardless of a person’s genetic predispositions to schizophrenia.
**Host:** That’s a big finding. So it doesn’t matter if someone has a family history of schizophrenia, cannabis use alone can still increase their risk?
**Dr. Chen:** Exactly. It appears that cannabis and genetic susceptibility to schizophrenia contribute to psychosis risk through separate pathways. Think of it like two separate roads leading to the same destination. [[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6861931/)]
**Host:** This research is the first to really quantify these independent risks?
**Dr. Chen:** That’s right. Dr. Edoardo Spinazzola, the lead author, explained that this is a groundbreaking study. They were able to use something called polygenic risk scores, which assess the combined effect of many genetic variants linked to both schizophrenia and cannabis use disorder. This allowed them to tease apart the individual contributions of each factor.
**Host:** So what advice would you give to our listeners based on this information?
**Dr. Chen:** It’s important to remember that correlation does not equal causation. We still need more research to fully understand the complex interplay between cannabis use, genetics, and psychosis. However, this study highlights the potential risks associated with frequent cannabis use, especially high-potency varieties. It underscores the importance of making informed decisions about substance use, particularly for those with a family history of mental health issues.
**Host:** Dr. Chen, thank you so much for shedding light on this important topic.
