Highly-potent cannabis is not being taken seriously enough by some liberal-minded parents, who would rather see their teens smoke pot than drink alcohol, a top psychologist has warned.
Sir Robin Murray, 77, a professor of Psychiatric Research at the Institute of Psychiatry (IoP), King’s College London, said around a third of the psychosis patents he sees at his practice in south London are caused by use of high-strength skunk.
The expert said the cases mostly involve young people, who often suffer from debilitating paranoia and hallucinations.
It comes as London is set to relax drug laws by no longer prosecuting young people caught in possession of cannabis – offering them educational courses on the drug’s dangers instead.
But results from European neighbours offer an insight into the potential pitfalls of such a policy – with Portugal seeing a huge surge in cannabis-induced psychosis after it decriminalised the drug in 2001.
According to research in the International Journal of Methods in Psychiatric Research, the number of hospital admissions in the country with a primary diagnosis of psychotic disorders and schizophrenia stemming from cannabis use soared by nearly 30-fold, from 20 a year in 2010 to nearly 590 in 2015 – and almost 90 per cent of these patients were men, whose average age was 30.
Sir Robin Murray (pictured) , 77, a professor of Psychiatric Research at the Institute of Psychiatry (IoP), King’s College London, said around a third of the psychosis patents he sees at his practice in south London are caused by use of high-strength skunk
The expert said the cases of cannabis-induced psychosis mostly involve young people, who often suffer from debilitating paranoia and hallucinations (file photo)
It comes as London is set to relax drug laws by no longer prosecuting young people caught in possession of cannabis – offering them educational courses on the drug’s dangers instead (Pictured: Cannabis farm which was busted in Coventry in June last year)
Sir Robin suggested the high number of cases in his practice are now impacting the facility’s ability to care for his patients.
He told the Times: ‘I think we’re now 100 per cent sure that cannabis is one of the causes of a schizophrenia-like psychosis.
‘If we could abolish the consumption of skunk we would have 30 per cent less patients [in south London] and we might make a better job of looking after the patients we have.’
Sir Robin works at the first NHS clinic in England to specifically treat cannabis smokers suffering from psychosis.
Running from Maudsley Hospital in Camberwell, south London, patients are typically seen for a minimum of 15 weeks, with treatment including one-on-one sessions with specialist therapists.
The aim of the clinic is to first help cannabis users wean themselves off the drug before helping them to manage without it – helped by weekly group therapy sessions with fellow patients and experts.
Sir Robin has praised the clinic, reporting it to be a success, even when services moved online due to the Covid pandemic.
It comes after he was part of the first team of researchers who proved a link between cannabis and mental illness among teenagers in the early 2000s – with many papers backing up his findings ever since.
Only two years ago, a study found that south London had the highest incidence of psychosis in Europe – and cannabis was said to be the largest contributing factor.
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The investigation, overseen by Sir Robin and published in The Lancet Psychiatry, found that those who smoked high-potency skunk were five times more likely to develop psychosis than those who did not smoke it.
According to the findings, rates of psychosis in London could be slashed by 30 per cent if skunk was taken off the streets.
Despite its potentially harmful effects, Sir Robin welcomed London’s plans to end prosecution of young people found in possession of cannabis.
The policy, set to be adopted by the Metropolitan Police, would see carriers of the drug offered educational courses on its dangers.
But Sir Robin wants more clarification over the scheme.
He said: ‘My questions will be: where will they get the counsellors who know anything about risks of cannabis?
‘What will happen if they don’t accept the counselling or go back to cannabis use?
‘And will it be accompanied by any education regarding the risks of cannabis — this is by far the most important thing.’
He added: ‘Because Lewisham is one of the proposed boroughs [where the scheme could first be introduced] we will be able to track the effects on psychiatric problems secondary to cannabis use — addiction, suicide attempts and psychosis.
‘But we need also to track road traffic accidents, street violence and visits to A&E departments for cannabis problems.’
Sir Robin said policy changes in other countries provided potential warnings for Britain.
In the state of Colorado in the US, there are now cannabis products available which contain more than 70 per cent THC – or tetrahydrocannabinol – the compound which gives users a high.
For comparison, traditional weed from the 1960s contained around 3 per cent or less THC, while the average in Europe and North America today is 10 to 15 per cent, according to an article by Sir Robin in JAMA Psychiatry.
Meanwhile, a study in Denmark found that alongside a rise in THC potency, cannabis-associated schizophrenia has increased by up to 400 per cent over the past two decades.
Sir Robin’s study in 2019 warned that 94 per cent of all cannabis available on the streets of London was in the form of skunk.
Researchers from King’s College London studied 2,100 people in 11 cities in Europe and South America in the biggest study of its kind.
They found that the link with psychotic disorders such as schizophrenia and paranoid delusion was strongest in London and Amsterdam – the two cities where high-potency cannabis is most commonly available.
Sir Robin said at the time: ‘If you are going to legalise, unless you want to pay for a lot more psychiatric beds and a lot more psychiatrists then you need to devise a system in a way that will not increase the consumption and will not increase the potency. Because that is what has happened in the US states where there has been legalisation for recreational use.
‘The critical question is whether medicinal use remains medicinal. The problem in California and Canada was that medicinal use became a synonym for recreational use.
‘You could go on the internet and tell a doctor, “I have headaches, I have back pain, I feel better if I have cannabis”. The main reason they legalised it was to try to control the amount of so-called medicinal use there, hoping that there would be a decrease in the use.’
The research, published in the Lancet Psychiatry journal, found that skunk – with a THC level of more than 10 per cent – increased the odds of psychosis 4.8-fold in a person who smoked every day compared with someone who never used the drug.
Using it more than once a week was less dangerous, but still increased the risk 1.6-fold.
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