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‘I thought cannabis should be legal, until I got psychosis and started eating out of bins'
For retired charity director Terry Hammond, 78, the distressing issue of cannabis-induced psychosis has come to dominate his life. Around 25 years ago, his bright, creative teenage son Steven, now 42, began smoking skunk – a highly potent synthetic form of the drug – at friends' houses, without his parents knowing.
'He was like so many young boys,' recalls Hammond from his home in Leicestershire. 'He was bingeing on it in secret and thought it would be fine.' But around six months later, in the autumn of 1999, Steven suddenly became paranoid.
'We were watching the BBC news, and he turned to me and accused me of ringing them. He was convinced the presenters were talking about him.'
The psychosis didn't stop there.
'He began to think aliens had taken over everybody,' adds Hammond. 'Then he began mumbling in an incomprehensible language, shouting at the walls and locking himself in his room. He was a boy gripped by absolute fear and terror, and his beautiful mind had just been destroyed.'
Not knowing how to cope with their now-delusional 6ft-tall son, Terry and his wife Christine, who also have a daughter, Victoria, kept him at home, but lived in fear he might commit violence or take his own life.
'At night, Steven would be screaming at the voices he heard,' Hammond says. 'I had to wash blood off the walls and carpet where he had been thumping his head against his bedroom wall. He had maniacal laughter, and at one point chased someone across the garden with a large piece of wood.'
At just 21, and with no family history of mental health problems, Steven was diagnosed with paranoid schizophrenia – essentially, psychosis that continues indefinitely. He spent three months in the department of psychiatry at the Royal South Hants Hospital in Southampton, where he was put on the antipsychotic drug Olanzapine and given talking therapy.
But even now – two decades on – Steven, who lives in a studio flat in his parents' garden, is still affected by his early drug use.
'He cannot work and struggles socially,' says Hammond, who has Steven's permission to share his story and has also written a book, Gone to Pot, to help others in similar circumstances. 'He is still on antipsychotic drugs but continues to hear voices, although he now has the skills to rationalise them.
'It has completely ruined his life, and as parents we have had to suffer the bereavement of losing our son. Fundamentally, it has damaged his brain for good. Young people need to know smoking cannabis is playing Russian roulette with brain damage.'
It is a harrowing and deeply personal story. But the issue of how to tackle the growing problem of ever-more potent cannabis on our streets is now causing division among those in power.
Sir Sadiq Khan recently backed a report by the London Drugs Commission stating that possession of small amounts of cannabis should be decriminalised. The Mayor of London said there was a 'compelling, evidence-based case' for decriminalisation.
But on July 7, Britain's leading police chiefs rebuked this and urged their officers to crack down on the drug.
Sir Andy Marsh, the chief executive officer of the College of Policing, said smelling the drug in towns and cities had an 'impact' on how safe he felt and was a sign of crime and disorder. His calls for tougher policing were endorsed by both Sir Stephen Watson, chief constable of Greater Manchester, and Serena Kennedy, chief constable of Merseyside.
Last month, David Sidwick, the Conservative police and crime commissioner for Dorset, wrote a letter to the police minister Diana Johnson – signed by 13 other police and crime commissioners – calling cannabis a 'chronically dangerous drug' that is just as harmful as cocaine and crack.
Such calls for a fresh approach come alongside evidence showing that cannabis-induced psychosis – where someone experiences hallucinations, delusions, and a loss of touch with reality – has substantially increased in recent years.
A 2019 study published in The Lancet by Prof Marta Di Forti shows that cannabis is now responsible for 30 per cent of first-time psychosis cases in south London (rising to 50 per cent in Amsterdam).
Further research, not yet published, by Dr Diego Quattrone and Dr Robin Murray, both professors of psychiatric research at King's College London, reveals that cannabis-induced psychosis in the UK is now three times more common than in the 1960s.
Their research suggests that 75 per cent of this increase is down to the use of skunk, which now accounts for 94 per cent of cannabis on the UK market.
'Across Europe, in the hubs with the highest cannabis consumption, namely London and Amsterdam, psychosis is up to five times more common than in other areas.' Dr Murray tells The Telegraph. 'Violence is also associated with psychosis, and of the psychotic people who go on to kill, 90 per cent are using either alcohol or cannabis.
'These are not typical domestic murders however. The people who become paranoid as a result of cannabis often have bizarre ideas, for example that God has told them to rid the world of evil, or that someone is persecuting them. And we know some of the multiple shooters in the US have been on high-potency cannabis.'
You do not need to look far to find examples of such drug-induced atrocities.
Most recently, Marcus Arduini Monzo, 37, was found guilty of murdering Daniel Anjorin, 14, with a samurai sword in Hainault, north-east London, while in a state of cannabis-induced psychosis.
In July last year, James Kilroy, 51, of Westport, Ireland, stabbed and strangled his wife Valerie to death. He said he was 'on a mission from God' after smoking cannabis for years.
Due to a lack of research, there is not yet unanimous consensus among experts that cannabis can be linked to violence, but a growing number believe this to be the case. Essentially, they attribute this to a key chemical component in the plant – tetrahydrocannabinol (THC) – which causes euphoria but also impairs attention, memory and learning, as well as triggering hallucinations and paranoid ideas in vulnerable individuals.
Worryingly – especially for young brains developing up to the age of 25 – the THC can remain in the brain for days or weeks, potentially causing long-term damage to its communication systems.
In another alarming trend, THC levels in cannabis have been rising over recent decades. In the 1960s, at the height of 'flower power,' THC levels in 'weed' (or weaker cannabis) were around 3 per cent. Today, most UK cannabis has THC levels of 16 to 20 per cent. In Holland, the figure is between 30 and 40 per cent, and in California, where cannabis is legal, levels can reach 80 per cent.
To Murray, this race to ever-stronger strains of cannabis should be a wake-up call. 'We know almost everything bad in America comes over here. And we know that where cannabis is legal, both the potency and consumption rates shoot up.
'It is not easy to get psychosis. Typically, someone may smoke skunk for five years before it kicks in. But in America, the THC is so strong, you can go psychotic in one night. It will hit those who already have a history of mental health problems the worst. We are braced for an epidemic of psychosis.'
This warning from both experts and police comes despite cannabis being supposedly illegal in the UK. Categorised as a Class B drug, someone caught in possession can face up to five years in prison and an unlimited fine. But in 2018, it became legal for NHS doctors to prescribe medical cannabis, and there has been a gradual relaxation of policing surrounding it – thought to be because underfunded forces are prioritising other issues.
The plant's pungent aroma is now commonplace in most cities. Meanwhile, the think tank the Centre for Social Justice (CSJ) reports that two thirds of police officers believe cannabis is fully or partially decriminalised in practice. (In 2018, the illegal cannabis market in Britain was estimated at £2.6 billion.)
Figures released under Freedom of Information show that in the year to September 2024, 68,513 people were found in possession of cannabis, but only 17,000 were charged.
For Dr Niall Campbell, a consultant psychiatrist at the Roehampton Priory Clinic, this relaxation in regulation – combined with increased potency – has led to a greater number of patients suffering psychosis.
'I don't think this rise is that surprising given how easy skunk is to buy online, and how ubiquitous it has become,' he says.
'Psychosis often begins with young people smoking a few joints and feeling a bit paranoid. But if they don't stop, over time they can reach a psychotic state which won't go away, even if they stop smoking. Sadly, this psychosis may last a lifetime and once people are told that they can get very depressed or suicidal.'
At the eight UK Addiction Treatment Group (UKAT) clinics across the country, it's a similar story. Patients typically stay for 28 days and, in more complex cases, up to six months, in residential facilities, with 35 per cent of patients each year funded by their local authorities. The cost for a 28-day inpatient stay at most UK clinics ranges from £8,000 to £16,000, while outpatient treatment costs between £2,000 and £4,000 per month.
In 2024, the group admitted 1,032 people for cannabis addiction, a rise of 20 per cent since 2019. They are also reporting an increase in younger patients – as young as 18 – addicted to cannabis and needing rehab.
Zaheen Ahmed, director of therapy at UKAT, says: 'I think people are trying to cope with life since Covid, and they are using cannabis to numb themselves. It is cheap, but the view that it is a harm-free drug is not true. The harmful effects can just be slow to appear, but we are now seeing a tsunami of patients with damage.'
Linsey Rafferty, 42, from Paisley near Glasgow, is one of those to have experienced damage first-hand. 'I started taking hash resin at 12,' she tells The Telegraph.
'And then moved onto stronger grass and skunk, with higher THC levels. I never thought it was bad for me.'
Rafferty had three short psychotic episodes over the decades she smoked, but in 2020, during the Covid lockdown, she suffered an extreme episode.
'I was hearing things and writing all over the walls of my home,' she says. 'I threw my phone away because I thought it had been tapped and was eating out of bins. It all made total sense to me at the time, and I can understand why people go violent.'
After six months of psychosis, a friend alerted mental health services, and Rafferty was sectioned and put on antipsychotics. Five years on, she has stopped smoking with the aid of the local charity Street Connect, which helps those who are homeless or struggling with addiction.
'When I stopped smoking, the psychosis went away. But still, the episode was deep and long-lasting, and the scars haven't gone. I never realised it could make me so vulnerable.
'I used to think drugs should be legalised, but not anymore.'
Despite stories like hers, however, Sir Sadiq is not alone in his calls to legalise cannabis.
Steve Rolles, senior policy analyst for the Transform Drug Policy Foundation, says: 'Scientists are finding consensus that things are getting worse under the current legislation. Cannabis is more potent, and there are more cannabis-related mental health problems. We feel that if we had responsible regulation with a legalised market that could control potency and put health warnings on products, similar to tobacco, then this may reduce the risks.'
But CSJ warns against this, cautioning of a drug-addiction crisis of 'unprecedented proportions.'
'The drug market is becoming increasingly dangerous – not just with more potent cannabis, but also opiates, and the emergence of xylazine, a deadly animal tranquilliser on the streets,' says Edward Davies, CSJ's research director.
'Funding for addiction services has been slashed by 60 per cent since 2012, leaving vast gaps in treatment availability.
'We are calling for urgent investment in treatment and recovery services, plus specialised clinics to address cannabis-induced psychosis. Law enforcement must also be empowered. Without decisive action, the crisis will continue to devastate communities across the UK.'
