Danger!

13Jun/117

Danger!

Harder to repair than a septum, but how likely is damage really? Picture credit: Artem Chernyshevych

Are the potential harms of many drugs overstated?

Recent military action in Libya ostensibly began with the aim of enforcing a no-fly zone to prevent aircraft being used against civilians, but quickly escalated into targeting Colonel Gaddafi and other members of the ruling family.

Back in the 50s, the Korean War started with the aim of saving the South from invasion by the Communist North, but the objective spread to attempted reunion of the peninsula.

The war on drugs appears to have suffered mission-creep too.

The Misuse of Drugs Act refers to drugs "capable of having harmful effects sufficient to constitute a social problem". If causing a social problem is the criterion, the law should arguably only apply to heroin, crack cocaine, and alcohol. (Whoever included hallucinogens as socially harmful, let alone as class-A drugs, must've been tripping. Then again, in the Newspeak of drug policy, "controlled" drugs are those for which control has been ceded to gangsters, so maybe we shouldn't make too much of the language.)

Yet in the response to the release of the Global Drug Policy Commission's report the week before last, the Home Office declared that there would be no change in policy because drugs are "harmful".

Well, so are a lot of things. Life without any risk at all would be a very dull one indeed.

In the 1993 action film Demolition Man, Sylvester Stallone plays an over-testosteroned cop who is cryogenically frozen and wakes up in 2032 in an anemic Los Angeles in which anything vaguely fun, from meat to swearing to physical contact (including sex), has been made illegal. Stallone's new partner, Sandra Bullock, is aching for something interesting to happen and soon gets her wish in the form of a psychopathic Wesley Snipes, also released from cryo-prison. Meanwhile, a band of outlaws lives underneath the city with their own rules, surviving on rat-burgers and petty theft. Their leader rails against the safety-tyranny of the nanny city-state thusly:

"I want high cholesterol. I wanna eat bacon and butter and buckets of cheese, okay? I want to smoke a Cuban cigar the size of Cincinnati in the non-smoking section. I want to run through the streets naked with green Jell-O all over my body reading Playboy magazine. Why? Because I suddenly might feel the need to, okay, pal? I've seen the future. Do you know what it is? It's a 47-year-old virgin sitting around in his beige pajamas, drinking a banana-broccoli shake, singing 'I'm an Oscar Meyer Wiener'."

A life that is potentially risky but fun, versus a state-controlled diet and wall-to-wall puritanism. Beer and pizza, or tofu and boredom. This blogger knows which he'd choose.

Anyway, one supposes that the implication of current policy is that drugs that are currently prohibited are so much more dangerous than anything else that we must be forcibly protected from them with the threat of prison. But it's not necessarily the case.

Looking at the relative fatality rates, amphetamines are only very marginally more dangerous than driving. Owing to HIV, sex is more likely to kill someone than ecstasy is. A year's average cocaine use is less risky than a full-body CT scan, which can very occasionally cause cancer. (The lifetime chance of a regular male smoker getting lung cancer, on the other hand, is higher than that of taking the bullet if playing Russian roulette with a six-shooter.)

It's essentially impossible to overdose with cannabis at all, and the drug's risks are not mortal ones. So, much of the prohibitionist argument focuses on its alleged effects on mental health – as has been the case in the past week or so first with John Rentoul's wrong-in-every-paragraph column in the Independent on Sunday and then this piece of wibbling in parliament by Charles Walker MP.

(They also both somehow managed to miss the point that the easiest way to control the strength of the drug and to restrict access to children is via legal regulation. Street dealers don't ask for photo ID, and nor do they have much of an idea of what it is they're selling.)

Walker's argument, such as it is, is based on a few anecdotes and a debunked link between a particular gene and the influence of cannabis on incidence of schizophrenia. Rentoul's initially rested on one single anecdote, of the experiences of his colleague Patrick Cockburn with his son Henry, although he did provide a link to an actual scientific study in a follow-up blog post in which he managed only to dig himself into an even deeper hole.

The paper in the British Journal of Psychiatry to which Rentoul refers claims to have found a definite causal relationship. Smoking cannabis, they claim, increases the risk of psychotic disorders, although not on its own:

"Cannabis use appears to beneither a sufficient nor a necessary cause for psychosis. Itis a component cause, part of a complex constellation of factorsleading to psychosis."

However, the experiments it reviews were predominantly cohort studies, and it is difficult to definitively prove a causal relationship without conducting a randomised controlled trial, and particularly with the low level of elevated risk involved – this blog post by UCL pharmacologist Prof. David Colquhoun brilliantly explains why, in the context of red meat and colorectal cancer.

Other studies came to a different conclusion. Mikkel Arendt of Aarhus University in Risskov, Denmark found that episodes of psychosis following cannabis use were indicative of predisposition to mental-health problems, and the subjects of his research "would have developed schizophrenia whether or not they used cannabis". Meanwhile, the use of cannabis has increased over the past few decades while the prevalence of schizophrenia has not, which it ought to have done if it were actually caused by cannabis use.

The scientific evidence is ultimately inconclusive. It could be that cannabis causes schizophrenia, just as it could be that those already predisposed to schizophrenia are more likely to use cannabis – just as 80% of sufferers smoke tobacco for its calming effects.

Should cannabis then be banned just as a precaution? Ignore for a moment the assumption this entails, that it is the job of the state to decide an acceptable level of risk for the individual, and consider the actual strength of the putative effect.

The paper referenced by Rentoul showed a doubled risk of schizophrenia. A meta-study in the Lancet suggested an increased relative risk of 40%, or by 200% in the case of the heaviest users. (Compare: the increased risk of lung cancer for regular cigarette smokers is 2000%)

But double next to nothing and you're still left with very little. If the relationship really is causal, then the absolute increase in risk would be from around 1 case per 100,000 people to, at most, 2 per 100,000. So even if decriminalisation led to a doubling of the number of cannabis users in the UK from around three million to six million, there would only be an additional 30 cases of schizophrenia in the entire country.

Sure, this would be thoroughly horrible for those suffering from the illness, but it's hardly the apocalyptic scenario of voices in every head that prohibitionists would have us believe. As a policy tool, criminalising three million people to prevent 30 from becoming ill is a sledgehammer to crack a handful of nuts. Not only is prohibition hypocritical and counterproductive, it is a totally disproportionate response.

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Update 14 June 2011: This post originally stated that the number of additional cases of schizophrenia would be 15. This has now been corrected.