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