In a small clinic in Denmark Hill, south London, a quiet revolution is taking place in the treatment of cannabis-induced psychosis. The Cannabis Clinic for Patients with Psychosis stands as the UK's only specialist service tackling both mental health crises and cannabis addiction simultaneously.
The Human Cost of High-Potency Cannabis
Isiah's story begins on a south London shopping centre roof in November 2023. The 29-year-old was moments from jumping, exhausted by paranoia that had grown alongside his cannabis habit. "I was very done," he recalls. "It felt there was no other route or option."
His journey into cannabis started aged 14, becoming daily by 17. At university during the pandemic, consumption increased. "Feelings of suspiciousness" emerged first towards housemates, then workmates. Isolation followed, with cannabis becoming both cause and coping mechanism.
Now, at the clinic's monthly brunch group surrounded by fidget toys and colouring books, Isiah represents a growing crisis. Despite hospital intervention and medication, he still uses cannabis daily while waiting for specialist support.
A Lone Beacon in Mental Health Care
The clinic's uniqueness seems remarkable given established links between cannabis and psychosis. A 2019 King's College London study published in the Lancet Psychiatry found 30% of new psychosis cases in London were linked to high-potency cannabis.
Dr Diego Quattrone, consultant at University Hospital Lewisham's psychiatric intensive care unit, reports at least 80% of new admissions involve cannabis use. He describes the drug's dangers as overlooked, noting its association with violence driven by psychotic symptoms.
The clinic was born from the persistence of Dr Marta Di Forti, professor of drug use, genetics and psychosis at King's. Working with two part-time practitioners, the service has helped 90 people since its NHS commission. Among those completing intervention, 74% stopped using cannabis, with 91% returning to education or work.
The Potency Problem and Waiting List Crisis
While cannabis use declines across England and Wales, those using are consuming more frequently. The Cannabis and Me study questioned 3,389 users, finding 50% were daily users consuming 17 joints weekly on average.
Dr Di Forti identifies potency as crucial. Forty years ago, cannabis typically contained 3% THC. Today, London's market is dominated by skunk-like cannabis averaging 14-16% THC. "My patients will tell you they can't get hold of low-potency cannabis even if they wanted to," she says.
Her husband, Professor Sir Robin Murray, describes the situation starkly: "I think we are at the beginnings of an epidemic." He compares it to early warnings about fast food and obesity, predicting increased psychosis as cannabis becomes more available and potent.
The clinic currently has 14 people waiting months for vital one-to-one sessions. "Of course it's dangerous," says Di Forti. "The chances of them getting a severe presentation of their psychosis and needing hospital admission is between three and four times greater."
Transforming Lives Through Integrated Care
Katie's story demonstrates the clinic's transformative potential. The 46-year-old grew up in care, first trying cannabis at eight and becoming a daily user by twelve. "I was self-medicating with it for many years," she says.
She heard intrusive, commanding voices from a young age. Smoking about 20 joints daily by twenty, she experienced her first hospital admission. "I was running down the Old Kent Road wearing fluffy pyjamas and nothing on my feet at 2am thinking I was God."
Over two decades, she was sectioned 50 times. Despite extensive medication and support, none targeted cannabis use specifically. A year after finding the clinic, she's now abstinent.
"I wouldn't say I'm better, but I'm a lot healthier - I'm able to do a lot more," she says. Her paranoia once prevented bus journeys; now she moves freely through London, sleeping and eating properly again.
The clinic's approach combines practical withdrawal support with psychological care. Senior practitioner Jodie Lynn explains techniques including role-playing difficult conversations, cannabis diaries to identify triggers, and cravings boxes for distraction.
Sleep emerges as a critical issue, with heavy users typically not dreaming. When dreams return during withdrawal, they can be terrifying. "It's just about supporting them through that," says Lynn.
As demand grows for this pioneering service, its integrated approach offers hope against what experts warn is a gathering storm of cannabis-related mental health crises across the capital and beyond.
