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Cannabis fuelling rise in psychosis among young adults

Dr Niall Campbell - Consultant Psychiatrist at Priory Hospital Roehampton - has issued a warning about the use of cannabis by young adults, and its link with paranoid psychosis.

His comments come as figures obtained by The Mail on Sunday show that cannabis has caused more than 125,000 NHS hospital admissions in the last five years. Around 15,000 of those cases involved teenagers – some of whom were rushed to A&E departments suffering serious psychosis.

Dr Campbell, who treats 18-year-olds and older, said 25% of the paranoid psychosis cases he sees are caused by the use of marijuana: “I am seeing an increasing number of young adults with paranoid psychoses – a schizophrenia-like illness and depression, which developed from marijuana use”.

The impact of cannabis on brain development

Teenagers are particularly vulnerable to cannabis because of their brain development.

The brain is still developing in the teenage years – up to the age of around 20. The Royal College of Psychiatrists says there is “a massive process of ‘neural pruning’ going on. This is rather like streamlining a tangled jumble of circuits so they can work more effectively. Any experience, or substance, that affects this process has the potential to produce long-term psychological effects”.

This, combined with the strength of today’s cannabis, can have a devastating effect on mental health, said Dr Campbell.

“We know the chances of developing mental illness from using cannabis are greatly increased depending on how young you are when you start smoking it, the more you smoke it, and the stronger it is,” he said, warning that the chemical profile of marijuana is “up to 100 times stronger than substances around in the 1960s – they have much stronger tetrahydrocannabinols (THCs) – the main psychoactive part of cannabis”.

In high doses, THCs can induce temporary schizophrenia-like psychotic symptoms such as paranoia, delusions, anxiety and hallucinations.

In spite of health and media warnings about health risks, many people still see cannabis as a harmless substance that helps you to relax and 'chill' - a drug that, unlike alcohol and cigarettes, might even be good for your mental health.

Studies on the effects of cannabis

In the US, recreational marijuana use is becoming more common, with its legalisation in nine states and the District of Columbia. Meanwhile Canada is about to become the second nation to fully legalise recreational cannabis.

But a new study has considered its effects on the adolescent brain.

Scientists at the University of Montreal found regular marijuana users, especially those who begin using it early in their lives, were far more likely to suffer repercussions in their thinking ability.

The study, in the American Journal of Psychiatry, followed more than 3,800 adolescents over four years. The teens, who started participating in the study when they were 13, agreed to provide annual reports of marijuana and alcohol use frequency and took cognitive tests that measured recall memory, perceptual reasoning, inhibition and short-term memory.

Students were assured that parents and teachers would not have access to the information unless their habits indicated an imminent risk to their lives. The study concluded that marijuana affected teenagers’ long-term cognitive abilities more than alcohol. And even after students reported stopping cannabis use, their brain function did not improve.

It was not the first study to suggest that early cannabis use may harm cognitive abilities.

In 2014, The Lancet Psychiatry famously reported that teens who smoke marijuana daily are 60 per cent less likely to graduate from high school or college than those who never use — and seven times more likely to attempt suicide.

And a 2017 study led by Josiane Bourque and colleagues at the University of Montreal suggested that a link between frequent marijuana use in adolescence and psychotic symptoms may be largely caused by depression.

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