Professor David Nutt's take on cannabis is a creed and not science
The evidence shows that cannabis is more damaging than Professor David Nutt believes, says Alasdair Palmer. To listen to some of the reactions to Alan Johnson's decision to sack Professor David Nutt, the Government's leading adviser on drugs, you'd think it was a re-run of the Catholic Church imprisoning Galileo for claiming that the Earth goes round the Sun.
But Prof Nutt isn't a martyr to science who lost his job
merely for confronting the Government with incontestable facts. He was sacked because, as Mr Johnson insisted, "he cannot be both a Government adviser and a campaigner against Government policy".
Prof Nutt and his supporters think that this just shows how unreasonable Government policy on drugs has become; if Mr Johnson was rational, he would change that policy so it was in line with the science and Prof Nutt's recommendations. But Prof Nutt's views on policy matters – for example, that the Government is wrong to classify cannabis as a class B drug (which means people convicted of possessing it can face five years in prison) – are not straightforward inferences from the scientific facts. It takes several additional steps, some of them highly debatable, to get to his conclusions.
Prof Nutt's own summary of the relevant science is itself far from uncontentious. For instance, he recognises that "cannabis is associated with an increased experience of psychotic disorders", which include schizophrenia, but he then minimises the significance, claiming that "schizophrenia seems to be disappearing, even though cannabis use has increased markedly in the last 30 years". But there is no consensus at all that schizophrenia is disappearing: on the contrary, most psychiatrists and psychologists think the incidence of the illness is increasing, or at least constant.
Furthermore, the best study on the relationship between cannabis and psychotic disorders, from Dunedin in New Zealand, found that teenagers who use cannabis heavily are significantly more likely to develop symptoms of psychosis. That finding is very much in line with the discovery that the brain keeps on developing until about the age of 22. After that, the detrimental effects of cannabis diminish. But before it, the risk that cannabis will trigger psychotic disorders is very real.
Prof Nutt does not seem to have recognised this important fact – which may explain why he thinks cannabis isn't a very dangerous drug and doesn't need to be classified as one. But while its use may not have consequences if you are Prof Nutt's age, it is definitely dangerous for young people.
Maxine Sacks, a clinical psychologist who works in north London, sees the damage cannabis can do to mental health on a regular basis. She notes that in societies such as India, where cannabis has been in widespread use for hundreds of years, there is a strong – and pretty effective – taboo against young people using the drug.
The harm that cannabis can cause in teenage brains is a good reason for, as the Government says, "erring on the side of caution" and classifying cannabis as a class B drug, with heavy penalties for those convicted of possession. The science does not force you to that conclusion – but then it does not force you to the conclusion that cannabis should be downgraded to class C.
And indeed, Prof Nutt's argument for downgrading cannabis has nothing to do with science at all: he simply claims that a higher classification may encourage youngsters to use the drug, because "it has greater cachet". He provides no evidence whatever for this claim.
He does agree, however, that "what we should be doing is to protect [young people] from harm at this stage of their lives". The Government thinks that imposing serious penalties for cannabis use is a reasonable way of achieving that goal.
So do I. Prof Nutt is entitled to take the contrary view, but he should not claim that it is merely the result of "science": it is about as scientific as advocating that handguns should be as freely available as swimming pools, because every year, fewer children get shot than drown.
Author: Alisdair Palmer
Date: 6th November 2009 (Archive)
Sorry about date (again) but I thought some 'Anti-Nutt' was in order to spark abit of debate.
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Nutt's Take on Cannabis is a Creed not a Science