‘There has been a campaign for decades to exaggerate the benefits of cannabis’

The legalisation and sale of medical cannabis in some US states and in Canada has led to much higher recreational use of cannabis without scientific proof that it is effectively treating specific conditions, according to an American journalist and author.

Alex Berenson, former New York Times journalist and author of Tell Your Children: The Truth about Marijuana, Mental Illness and Violence, said that there are almost no medical benefits of cannabis in randomised controlled trials. "There has been a campaign for decades to exaggerate the benefits of cannabis in the US and underplay its harms," said Alex Berenson at a public talk in Dublin.

According to Berenson, the medical benefits of Tetrahydrocannabinol (THC) – the psychoactive compound in cannabis – have been overstated. "In California, men with HIV, women with breast cancer and people with motor neurone disease were among campaigners for medical cannabis yet there are almost no medical benefits of cannabis from randomised controlled trials while the use of THC extracts has increased."

Over 90 per cent of those authorised for medical cannabis in the United States, according to Berenson, are recreational users. "The only widespread condition that cannabis is useful for is the treatment of pain but when you legalise a medicine for pain, you are effectively opening the door to its widespread use," he said.

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CBD

Berenson did, however, acknowledge that there are medical benefits to cannabidiol (CBD) which is the non-psycho active compound in cannabis used to treat specific severe types of epilepsy. Drugs such as epidiolex are approved in the US for the treatment of spasticity in multiple sclerosis, nausea from chemotherapy and seizures in people with Lennox-Gastaut syndrome or Dravet syndrome. These drugs, although used by a tiny number of patients here, have not yet been approved by the European Medicines Agency.

Berenson also pointed to research – including studies by Irish psychiatrist professor Mary Cannon – which found links between cannabis use in teenage years and adult psychosis. Some studies also point to a higher risk of schizophrenia among cannabis users. "Synthetic cannabinoids can cause psychosis even with those with no pre-existing mental illness," said Berenson who was speaking at a public talk, Cannabis and Youth Health: the Evidence, at the Royal College of Surgeons of Ireland.

Dr Garrett McGovern, an addiction specialist in Dublin, said that being intolerant of young people using drugs won’t solve the problem. “This country is awash with recreational drugs. We need to look at harm reduction – such as testing drugs at music festivals. Alcohol and tobacco are still much bigger problems in Ireland.”

Prof Susan Smith from the department of general practice at the RCSI and a GP in Inchicore, Dublin, said that a lot of parents think cannabis is okay. "They don't realise that it is much more potent now and daily use can make young people sleepy, confused, dizzy and anxious. About 17 per cent will become dependent on it but psychosis is rare."

Prof Cannon said that there were proven effects of cannabis on memory, concentration and the ability to learn. "Heavy cannabis use has a worse effect on education and financial outcomes than alcohol use," she said.