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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Wednesday 9th November 2011

I listened to an item on the radio about a local authority insisting that all taxis in its area are fitted with CCTV cameras that must be functioning 24 hours a day every day. Some owner drivers are unhappy that they will be recorded even if they are using the vehicle privately, to go to the shops or the cinema with their family. This sort of discussion usually produces statistics about how many CCTV cameras there are in the UK and how it ‘is just like 1984’.

That set me thinking about one aspect of modern live that is not like 1984 and, just possibly, that is a shame. If you’re familiar with the book, you’ll know that part of the way society is run is that history is constantly rewritten to suit current thinking. I’m tending to think that such revision is not universally a bad thing.

Rheum x hybridum, rhubarb

Rheum x hybridum, rhubarb

I’ll start with a 19th century example. In 1846 the Gardeners’ Chronicle contained a letter from the head gardener at Alton Towers saying that rhubarb leaves, from Rheum x hybridum, had been used for many years as a vegetable. Rhubarb leaves are toxic and there are numerous reports of deaths, especially during the two world wars when people turned to it at times of shortage. A later edition of the publication contained a correction pointing out that it should have said ‘stalks’ not ‘leaves’.

And here’s where re-writing history would be useful. If you read the original without knowing about the correction you might be inclined to try adding rhubarb leaves to your diet. You might, today, accidentally repeat the error if you didn’t do the research necessary to find it had been a mistake. Worse, you might choose to ignore the correction and repeat the lie.

And that brings us to Cannabis sativa. In 2005, a paper appeared claiming that a genetic link related to the catechol-methyl-transferase (COMT) gene had been found between cannabis use and psychosis and that one in four people carried this genetic variation and was, therefore, at risk of mental illness as a result of any cannabis use.

Cannabis sativa, marijuana

Cannabis sativa

As you would expect from a scientific paper, the authors conclude that they have provided evidence suggesting that there may be some susceptibility. As you would also expect, prohibitionists leapt on this paper as proof of a genetic link and pressed the argument that a one in four risk was higher than the risk of playing Russian roulette and that here’s a proof that cannabis was a harmful substance worthy of high classification. Coming, as it did, during the debate about classification, this paper was used to support the argument for cannabis being classified as Class B.

There’s a problem, however. Later work trying to replicate the results found in 2005 has failed and there have been a number of papers showing that this apparent genetic link does not exist. A number of those papers, as you might expect, said that they had found no link but they wouldn’t go as far as to say they had proved there was no link.

The most recent edition of the British Journal of Psychiatry, however, contains a paper which unequivocally states ‘There was no evidence of an interaction…between cannabis use and COMT’. The full paper is behind a paywall but this link is to the abstract.  The authors go on to draw the somewhat suspect conclusion that this means that the risk of psychosis from cannabis use is universal i.e. the one in four risk becomes four in four but that’s a different debate.

Cannabis sativa, marijuana

Cannabis sativa

You might think that anyone posing as expert on the subject of the effects of cannabis would want to take account of all the latest work but, unfortunately, you would be wrong. The US government funded ‘National Institute of Health’ has a web page entitled ‘Research Report Series – Marijuana Abuse’.   This page begins with a section entitled ‘Is There a Link Between Marijuana Use and Mental Illness?’ that quotes extensively from the 2005 paper without any mention of the later papers that have contradicted those findings.

I know it may take time for a web page to be updated so it is unfair to expect a paper only recently published to be included but it is clear that the current page was produced during or after 2009 and by that time the COMT gene theory had already been discredited.

It is tempting to wish that we could re-write history so that the 2005 paper would no longer be available for people to rely on or that there should be some way to electronically tag disproved research so that anyone linking to it would be shown to be misrepresenting matters. But there are all sorts of reasons for that to be impossible.

Just as, it seems, it is impossible to expect those who claim to be offering the truth about substances to stick to the truth and not attempt to pervert the basis of science by using it to create the lies that suit their agenda.


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