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Teens who use high-THC cannabis are twice as likely to experience psychotic episodes
Last reviewed: 02.07.2025
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Young people aged 16 to 18 who use high-potency cannabis such as 'skunk' are twice as likely to experience psychotic symptoms when they are aged 19 to 24 compared to those who use low-potency cannabis, according to new research from the University of Bath published in the scientific journal Addiction.
Previous research by the Addiction and Mental Health Group at the University of Bath has shown that the concentration of THC (delta-9-tetrahydrocannabinol) in cannabis – the main psychoactive component of cannabis – increased by 14% between 1970 and 2017. This means that the UK cannabis market is now dominated by high-potency strains such as 'skunk'.
This new study is the first longitudinal study to examine measures of early adolescent psychosis and to analyze the potency of cannabis in detail.
The findings are based on the Children of the 90s study, the largest research project of its kind. It began in Bristol more than 30 years ago, collecting information and data from thousands of families across the city.
The study included almost 14,000 people from birth, many of whom continue to participate today. Between the ages of 16 and 18, participants were asked about their recent cannabis use. By age 24, they reported their main type of cannabis and any psychotic experiences, such as hallucinations or delusions.
Lead author Dr Lindsay Hines, from the University of Bath’s Department of Psychology, said: “Young people who use high-potency cannabis are twice as likely to experience psychosis-related experiences, such as hallucinations and delusions. Importantly, the young people we asked had not previously reported such experiences before starting to use cannabis, confirming that high-potency cannabis use can have negative impacts on mental health.”
This study complements the extensive research being conducted as part of the ALSPAC study, which covers topics ranging from the link between medication use during pregnancy and the well-being of the child to the impact of social media on suicide.
The main findings of this study are:
- 6.4% of young people who used cannabis had new psychotic experiences, compared with 3.8% of non-users.
- After initiating cannabis use, 10.1% of young people using high-potency cannabis reported new psychotic experiences, compared with 3.8% of low-potency cannabis users.
- Those who used high-potency cannabis were more than twice as likely to report new psychotic experiences after starting cannabis use, compared with those who used low-potency cannabis.
This study adds to a growing body of evidence that high-potency cannabis use is associated with an increased likelihood and now frequency of psychotic experiences.
The researchers call for better data on the long-term effects of high-potency cannabis use and for policies to reduce the potency of cannabis available to young people.
Dr Hines said: "Cannabis is changing and high potency cannabis is becoming more widely available. These findings highlight how important it is to understand the long-term effects of high potency cannabis use in young people. We need to improve the way we educate and inform young people about the impact of cannabis use in the 21st century."