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Peter Reynolds

The life and times of Peter Reynolds

A CLEAR Response to the Institute of Psychiatry’s Latest Cannabis and Psychosis Scaremongering

with 2 comments

Dr Marta di Forti

The Insititute of Psychiatry is today announcing its latest study on the links between cannabis and psychosis – ‘The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study’.

For many years, its leading lights Professor Sir Robin Murray and Dr Marta di Forti have published study after study attempting to show a causal link between cannabis use and psychosis.  They have never managed to achieve this and despite concerted efforts, the link cannot be described as anything more than extremely tenuous.  The number of people that may be affected is infinitesimally small, while hundreds of millions of people worldwide consume cannabis regularly without any ill effects.

Every year in the early spring Dr di Forti and Professor Murray publish their latest study on the subject. It’s always interesting to see the latest iteration of their work although all the studies are remarkably similar

Cannabis is a psychoactive substance so clearly it can have an effect on mental health.  We know from at least 10,000 years of human experience that for most people this is a beneficial effect.  The number of people that suffer negative effects is difficult to quantify but we can be certain that it is very small. Research published in the journal Addiction shows that in order to prevent just one case of psychosis, more than 20,000 people would have to stop using cannabis. http://onlinelibrary.wiley.com/doi/10.1111/add.13826/full

This level of risk must be compared with other risks to give it any meaning. For instance, if the risk of a diagnosis of psychosis correlating with cannabis use is 1 in 20,000, the risk of being struck by lightning in one’s lifetime is about 1 in 3,000. This puts the risk into a realistic perspective.
https://news.nationalgeographic.com/news/2004/06/0623_040623_lightningfacts.html

It’s also important to understand that this latest study does nothing to show that cannabis actually causes psychosis, only that there is an association or correlation with cannabis use.  There may be other correlations which may or may not be much stronger.  For instance the populations studied may also use tobacco, drink wine, eat spicy food, live in a city centre or exercise regularly or not at all.  Similarly it cannot be shown that any of these factors are the cause of psychosis.

It is also interesting that the study deems an average of 14% THC to be high potency cannabis.  Throughout the USA and Canada, average THC content now exceeds 20%, sometimes as high as 35% and there is no reported increase in rates of psychosis.

Finally, it has to be said that Dr di Forti is well known for her theoretical projections about cannabis use which can be quite alarmist. Thankfully, they have never been reflected in actual healthcare records and the number of cases of psychosis correlating with the use of natural cannabis in the UK remains very low, no more than a few hundred.  There are many, very much more risky activities to be concerned about.

What is certain is that the way safely to manage the risks of cannabis, even though they are so low, is in a legally regulated environment. In this case products are labelled so that the content is known, quality is maintained to a standard avoiding contamination and impurities and if anyone does experience problems they can seek help without having to confess to a crime. Age limits can also be enforced ensuring that children do not have the easy access to cannabis that they have, for instance, in the UK.

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Written by Peter Reynolds

March 20, 2019 at 10:27 am

2 Responses

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  1. Well said! It seems to me that they are more worried about their jobs and reputation than reducing harm! I wonder if they’re seen a burning bush or heard the word of God to be so single minded about what really is a moral stance in their view!

    Stephen Brophy

    March 20, 2019 at 11:36 am

  2. Today most people smoke Cannabis or have smoked at some time to try it, when I was a youth in the 70’s we were definitely in a minority, in the 80’s I noticed people from school who were straight were now regular herb smokers.
    By the 90’s more and more people were smoking herb, simply because they realised it was not addictive and it was much easier to score discreetly, and now we find it has become ubiquitous and most people today smoke or have smoked and tried Cannabis for themselves and know it does them no harm.
    So it is no surprise that most people who present at a clinic with psychosis have smoked Cannabis at some point in their lives, just like the rest of the population today who do not have mental health issues.
    The incidence of people with or suffering from psychosis has not increased in any shape or form these people are talking folly, about crap they believe.
    Yet your average Babylonian knows through experience Cannabis is harmless, they did not need a degree to deduce this fact, it aint rocket science.

    Pete

    March 24, 2019 at 4:27 pm


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