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London Clinic Tackles Psychosis Linked to Potent Cannabis Use
16 Nov
Summary
- 30% of new psychosis cases in London linked to high-potency cannabis
- Cannabis Clinic offers specialized "dual-diagnosis" support for psychosis and addiction
- 74% of clinic's patients stop using cannabis, 91% return to work or education
As of November 2025, a specialized clinic in London is at the forefront of addressing the alarming rise in psychosis cases linked to high-potency cannabis use. According to a 2019 study, 30% of new psychosis diagnoses in the city are associated with the consumption of weed containing 10% or more tetrahydrocannabinol (THC).
The Cannabis Clinic for Patients with Psychosis is the only facility of its kind in the UK, and possibly the world, offering a "dual-diagnosis" approach to tackle both psychosis and cannabis addiction simultaneously. Since receiving a commission from the South London and Maudsley NHS foundation trust in 2023, the clinic has helped 90 people, with 74% of those who completed the program successfully quitting cannabis use. Furthermore, 91% of this group have returned to education or employment.
Despite the clinic's impressive results, its services are in high demand, with a waiting list of 14 people as of mid-November 2025. Clinical lead Dr. Marta Di Forti warns that the delay in accessing the clinic's vital one-on-one sessions significantly increases the risk of patients experiencing severe psychotic episodes and requiring hospital admission.
The clinic's integrated approach addresses the practical and psychological challenges of cannabis withdrawal, providing support through group sessions, role-playing exercises, and cannabis diaries. Patients also learn to manage the often-terrifying return of dreams and hallucinations that can occur during the quitting process.
While overall cannabis use in London has declined in recent years, those who do use the drug are doing so more frequently, with a 2019 study finding that 50% of users were daily consumers, averaging 17 joints per week. Experts attribute this trend to a decreased perception of harm, driven in part by the increased availability of medical cannabis prescriptions, even though the NHS only approves it for a small number of conditions.
The high potency of modern cannabis, with some strains containing up to 16% THC, is a key factor behind the rise in psychosis cases. As the clinic's work demonstrates, an integrated approach to tackling both addiction and mental health issues is crucial in stemming this growing crisis.
