Earlier this year, Professor Glyn Lewis of the University of Bristol, one of the foremost authorities on the subject confirmed “…there is no certainty of a causal relationship between cannabis use and psychosis”. He reviewed all the published research and announced in the journal Addiction in 2009 that the risk of psychosis from cannabis use is at worst 0.013% and perhaps as little as 0.0030% – http://www.ncbi.nlm.nih.gov/pubmed/19832786.

In 2009, specifically in response to tabloid scare stories about cannabis and psychosis, the ACMD commissioned Keele University to look at the evidence. The study looked at almost 600,000 subjects and concluded that despite increased consumption of more potent cannabis, “the incidence and prevalence of schizophrenia and psychosis was either stable or declining”.

5. In an attempt to rebut this point, the IOS quotes the conclusion of the study of 1900 people referred to:

‘Cannabis use is a risk factor for the development of incident psychotic symptoms. Continued cannabis use might increase the risk for psychotic disorder by impacting on the persistence of symptoms.’

Again, this does not support the assertion made in the article at all. This is about “incident psychotic symptoms” and “subclinical symptoms”, nothing to do with the article’s inaccurate misleading and distorted assertion that “cannabis can be the precipitating factor for a sizeable minority of the population, perhaps 20 per cent, with a genetic predisposition to psychosis.”

6. In the ninth paragraph, the article states “…for people genetically susceptible to psychosis, the risks involved in taking cannabis may be lethally high. Cigarettes and alcohol, whatever harm they cause, do not send you mad.”.

Although the article is presented as a comment piece, that does not absolve the publishers of their responsibility “…not to publish inaccurate, misleading and distorted information” which this clearly is.

Cannabis has no realistic lethal effects and use of the word “lethal” is unambiguous. Psychosis is not a lethal condition. This claim is entirely false. The therapeutic ratio is the scientific measurement of toxicity – effective dose:lethal dose. The therapeutic ratio of alcohol is 1:20, of aspirin 1:35, of cannabis 1:20000. It is impossible to ingest a lethal dose of cannabis.

7. In an attempt to rebut this point, the IoS has suggested that “‘the risks involving cannabis may be lethally high’ as psychosis can, of course, lead to potentially lethal actions of self harm, injury or suicide.”.

This is not an accurate quotation from the article which actually says “…the risks involved in taking cannabis…” which is a different thing.

If the article intended to mean there might be “potentially lethal actions of self harm, injury or suicide.”, then why did it not say so? To say what it did was self-evidently misleading and distorted.

Cigarettes are a far higher risk factor for psychosis than is cannabis. 80-90% of diagnosed schizophrenics smoke cigarettes – http://brainblogger.com/2009/07/03/why-do-schizophrenics-smoke-cigarettes/.  Alcohol is a proven cause of psychosis, 1-2% in Korsakoff”s syndrome. There is therefore far more evidence suggesting that cigarettes or alcohol send you mad than there is for cannabis.  Mr Cockburn’s assertion is entirely false.

8. It is obvious that either Mr Cockburn and the IoS do not properly understand the research they are citing or they are deliberately distorting it to support their sensationalist theories. These studies use precise language which Mr Cockburn has hacked and distorted into simplistic certainties which are entirely false.

9. Prior to making this complaint I tried to engage with the Independent on Sunday (IoS) in an effort to obtain either a correction or the opportunity to submit a letter for publication. I wrote to the IoS as follows:

“As promised, here is a draft of my proposed PCC complaint concerning John Rentoul’s article on 5th June 2011. I shall also forward you shortly a draft complaint concerning Patrick Cockburn’s article.

I think the point here is that both these articles were seriously “inaccurate, misleading and distorted”. They completely misrepresent the scientific evidence about cannabis and are little more than scaremongering and propaganda.

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