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Psychosis linked to cannabis use


One in six cases of psychosis are linked to cannabis use, claims psychiatric expert


  • Professor Robin Murray said that smoking cannabis is linked to psychosis
  • He said 50,000 people have the condition due to smoking cannabis as teenagers  
  • His comments follow a renewed debate over the legalisation of the drug

A psychiatric expert has claimed one in six people with psychosis in Britain would never have developed it if they had not smoked cannabis.


Professor Robin Murray, an authority on schizophrenia at King’s College London, said about 50,000 people were now diagnosed as psychotic solely because they used the drug 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 academic’s comments follow a renewed debate over the legalisation of the drug, following the first ever NHS prescription for cannabis oil being given to 12-year-old Billy Caldwell to treat his epilepsy last week.


The Royal College of Psychiatrists has also spoken out to warn that cannabis use doubles the risk of someone becoming psychotic, after former Tory leader William Hague suggested it 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 or 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.’



  • Source:  https://www.dailymail.co.uk/sciencetech/article-5881123/Psychiatric-expert-claims-one-six-people-psychosis-linked-cannabis-use.html