Research aired on BBC’s Panorama last night suggests that teenagers who use cannabis are more likely to develop schizophrenia than those who do not.
The research was based on studies that took place in Sweden and New Zealand monitoring people over a number of years. The Swedish study, published in 1987, analysed the medical records of 50,087 men, concluding that those who had smoked cannabis before being called up for national service were more likely to be hospitalised with schizophrenia than non-users; the New Zealand study found that those who had taken cannabis three or more times before the age of 15 were more likely to suffer symptoms of schizophrenia by the time they were 26.
Speaking on the programme Professor Robin Murray of the Institute of Psychiatry said there was more and more anecdotal evidence, as well as statistical evidence, suggesting a link between cannabis use and psychosis:
“I was seeing patients who had been very normal as children, who had been great at school, academically successful, sociable, very sporty, really kids that every parent would be proud of – and then they went psychotic.”
Responding to the research Bill Walden-Jones, Chief Executive of Welsh mental health charity Hafal, stated: “We always advise people not to use illegal drugs. Common sense says that if someone is vulnerable to mental illness then taking something that affects the thinking process could cause problems – and of course you don’t necessarily know if you are vulnerable.
“However, we should be careful not to take a one-track view when considering the causes of schizophrenia. We must look very closely at the evidence, and encourage more research, before we conclude that cannabis is a major cause of this severe mental illness. It is of course not in dispute that many people who develop schizophrenia have not taken cannabis. Hafal is concerned that the stigma of severe mental illness is not increased by any unproven suggestions that ‘they brought it on themselves’.”
For more information on the Panorama programme, go to: news.bbc.co.uk