Britain could set off a schizophrenia timebomb if it ignores the dangers of super-strength ‘skunk’ cannabis

Britain could set off a schizophrenia timebomb if it ignores the dangers of super-strength ‘skunk’ cannabis, one of the UK’s most eminent psychiatrists warns today.

Strong evidence now shows that smoking potent forms of the Class B drug increases the chance of psychosis, paranoid delusions and schizophrenia.

But too many people – from teenagers to top officials – have little idea of the terrible toll it can take on the mind, says Professor Sir Robin Murray.

Labour, the Liberal Democrats and the Scottish National Party all back legalisation of cannabis in some form. But Prof Murray said the dangers were not being recognised – and legalising skunk would amount to ‘a major pharmaceutical experiment’ with the brains of young people.

Prof Murray, from the Institute of Psychiatry at King’s College London, said: ‘I don’t think any serious researcher or psychiatrist would now dispute that cannabis consumption is a component cause of psychosis.’

He warned that:

MRI scans show long-term use of skunk can shrink a vital part of the brain;

The substance – now dominant on Britain’s streets – is four times stronger on average than cannabis smoked in the past;

A clear majority of studies show those who regularly smoke cannabis are at ‘significant increased risk’ of developing psychosis or schizophrenia-like illness;

Heavy users of skunk are up to four times more likely than non-users to develop psychotic symptoms.

Prof Murray said the cannabis being sold on our streets had changed almost beyond recognition in the past 20 years. Dealers have dropped weaker varieties in favour of skunk, which is made from non-pollinated parts of the plant, and provides a stronger ‘hit’ that may be more addictive.

A recent study revealed that almost all cannabis sold in the UK is now skunk. On average, skunk is 16 per cent tetrahydrocannabinol (THC), the main psychoactive compound – four times more than the THC in marijuana and hash.

Brain scans show skunk has a far stronger impact on the mind, said Prof Murray, due to both its high THC content and its very low content of the protective compound cannabidiol.

Experiments on volunteers at King’s College show THC boosts the brain’s natural fear response – making the merely worrisome seem positively frightening.

And MRI scans reveal that long-term use of skunk shrinks the hippocampus – the part of the brain essential for regulating emotions and long-term memory – by 11 per cent, according to researchers at Monash University in Australia. Only ‘prolonged abstinence’ could reverse the brain atrophy, they concluded.

MRI scans reveal that long-term use of skunk shrinks the hippocampus – the part of the brain essential for regulating emotions and long-term memory – by 11 per cent

Prof Murray and colleague Dr Marco Colizzi have emphasised their concerns in a hard-hitting article for the British Journal Of Psychiatry, titled Cannabis And Psychosis: What Do We Know And What Should We Do?

They say UK authorities should watch what happens in America, where a number of states have recently legalised cannabis use.

‘The USA has embarked on a major pharmaceutical experiment with the brains of its youth and we should wait and see the outcome of the experiment,’ they write. ‘While we wait, we need education to make the public aware of the risks associated with heavy cannabis use.

‘It would be a shame when we are in sight of ridding the country of the scourge of tobacco use, if it were to be replaced by use of a drug that, although less harmful to the body, is more toxic to the mind.’

To help educate people about the dangers, Prof Murray is giving a series of talks in London, organised by events company Funzing. And he believes that health officials should be playing a far more active role in warning of the perils of skunk.

His intervention comes three years after The Mail on Sunday revealed his groundbreaking research suggesting up to a quarter of all new psychosis cases could be caused by skunk. Among those deeply affected is hereditary peer Nicholas Monson, whose son Rupert, 21, took his own life last year after developing drug-related psychosis.

Lord Monson said: ‘He descended into complete, utter madness.’

Rupert Green (pictured) the son of Lord Monson, was just 21 when he killed himself last year after descending into drug-related pyschosis, having gone in a few short years from ‘the occasional spliff’ to habitually smoking skunk

Rupert first admitted smoking ‘the occasional spliff’ at 19 and, like many parents, his father reacted with relief that it was nothing harder. But his behaviour gradually became ‘more and more peculiar’, said Lord Monson, adding: ‘He was a mixture of self-pity and outright aggression. I found him very difficult to deal with.’

The family managed to get Rupert referred to an NHS mental health team, and after being diagnosed, the youngster stopped smoking skunk and went on medication. However, he later killed himself.

Lord Monson said: ‘He hadn’t touched skunk for four months. But his mind continued to be overwhelmed. What I’ve learnt since his death is once a young man gets into a state of drug-induced psychosis, he doesn’t get out of it.’

Lord Monson has lobbied hard for better public education, including writing to the Prime Minister. He said he wanted cannabis below five per cent THC legalised to take it out of criminals’ hands, but anything stronger to be banned.

Incredibly, Government agencies provide almost no information on the risks of skunk, despite millions smoking it. Three years ago, the Advisory Council on the Misuse of Drugs said there was ‘strong evidence’ that ‘standalone’ information or warning campaigns were ‘ineffective’. But Lord Monson said: ‘The Government is doing an enormous disservice by not educating people about skunk’s dangers.’

Last night Public Health England said its Rise Above programme helped young people cope with a range of ‘diverse challenges’ including drug misuse, while its dedicated drug information website, Talk To Frank, provides ‘easily accessible information for young people about the risks and harms of drug misuse’.

Yet Rise Above, which is aimed at teenagers, does not mention cannabis at all. Talk To Frank, for an older audience, does state that regular cannabis use is ‘associated with an increase in the risk of later developing psychotic illnesses including schizophrenia’. But it contains no information on the greater danger posed by skunk.