DNA tests could be used in the future to flag up cannabis smokers at risk of psychosis, a study has found.
Researchers at King’s College London and Exeter University found that high-potency cannabis leaves a distinct mark on DNA, which could provide insight into the biological impact of using the drug.
High-potency cannabis is defined as having tetrahydrocannabinol (THC) content of 10 per cent or more. THC is the psychoactive component of cannabis and causes users to feel high, but it can also cause anxiety and paranoia in higher doses.
Scientists have previously warned that some people who smoke strong cannabis may be at greater risk of developing psychosis or schizophrenia, but the extent of the risk is contested.
Teenagers are thought to be at particular risk of psychosis as the brain is developing during adolescence.
Police have previously warned that most cannabis being sold illegally in the UK is highly potent, with high levels of THC and low levels of cannabidiol (CBD), an antipsychotic substance.
The researchers said their study showed that the effect of cannabis use on DNA is different in people experiencing their first episode of psychosis compared to users who have never experienced psychosis.
This suggests there could be potential for DNA blood tests to help characterise those cannabis users at risk of developing psychosis to inform preventative approaches, they said.
Senior author Marta Di Forti, Professor of Drugs, Genes and Psychosis at King's said, "With the increasing prevalence of cannabis use and more availability of high-potency cannabis, there is a pressing need to better understand its biological impact, particularly on mental health.
"Our study is the first to show high-potency cannabis leaves a unique signature on DNA related to mechanisms around the immune system and energy production. Future research needs to explore if the DNA signature for current cannabis use, and in particular the one of high-potency types, can help identify those users most at risk to develop psychosis, both in recreational and medicinal use settings."
A team at Exeter University also looked at the effects of cannabis use on DNA methylation—a chemical process detected in the blood that alters how genes are functioning.
They analysed DNA from blood samples from both people who have experienced first-episode psychosis and those who have never had a psychotic experience.
The analysis showed that frequent users of high-potency cannabis had genetic changes which could affect energy and immune response.
Dr Emma Dempster, Senior Lecturer at the University of Exeter and the study's first author, said, “This is the first study to show that frequent use of high-potency cannabis leaves a distinct molecular mark on DNA, particularly affecting genes related to energy and immune function.
"Our findings provide important insights into how cannabis use may alter biological processes. DNA methylation, which bridges the gap between genetics and environmental factors, is a key mechanism that allows external influences, such as substance use, to impact gene activity. “These epigenetic changes, shaped by lifestyle and exposures, offer a valuable perspective on how cannabis use may influence mental health through biological pathways."
