CANNABIS DEBATE

As debate in Britain is renewed over the legalising of cannabis, a leading academic has claimed that the drug is linked to psychosis.

THERE has been renewed debate in Britain over the legislation of cannabis. Last week, for the first time ever, the NHS prescribed cannabis oil for 12-year-old Billy Caldwell to treat his epilepsy.

But a psychiatric expert, Professor Robin Murray, an authority on schizophrenia at King’s College London, has claimed that one in six people with psychosis in the UK would never have developed it if they had not smoked the drug. The leading academic said about 50,000 people were now diagnosed as psychotic solely because they used the substance while teenagers. Many had no family history of psychosis and would have had no risk of developing the disease if they had not smoked ‘high-strength cannabis’, he claimed.

The Royal College of Psychiatrists has also spoken out to warn that cannabis use ‘doubles the risk’ of someone becoming psychotic. The warning was given following comments made by former Tory leader William Hague who said the drug should be decriminalised for recreational use.

Professor Murray said: ‘If you smoke heavy, high-potency cannabis, your risk of psychosis increases about five times.

‘A quarter of cases of psychosis we see in south London would not have happened without use of high-potency cannabis. It is more prevalent in that area, but the figure for Britain would be one in six – or approximately 50,000 people.’

Cannabis can make users feel paranoid, experience panic attacks and hallucinations, and it is also linked to depression and anxiety. Many experts claim it is only people who are predisposed to psychosis who develop it after smoking cannabis. However, Professor Murray added: ‘It is true there are some people with a family history of it who are pushed into psychosis more easily by smoking cannabis. But most have no family history, there is no evidence they are predisposed to schizophrenia or psychosis. The problems start only when they are 14 and 15 and start using cannabis.’

It is believed the drug disrupts dopamine, a brain chemical which helps people predict what is going to happen and respond rationally. In developing brains, cannabis can skew this so that people become paranoid and deluded.

Dr Adrian James, Registrar at the Royal College of Psychiatrists, said: ‘As mental health doctors, we can say with absolute certainty that cannabis carries severe risks. The average cannabis user is around twice as likely as a non-user to develop a psychotic disorder.’