Faculty of 1000

Post-publication peer review

Posts Tagged ‘cannabis’

The drugs don’t work

Posted by rpg on 2 March, 2010

A copy of ‘People & Science’, the publication of the British Science Association appeared on my desk this morning. (Aside: what is it with these people? Founded in 1831, they used to be known as the British Association for the Advancement of Science, or the BA, and set out to combat the perceived elitism of the Ri. Fair enough, but they had a massive re-branding exercise last year and now have a logo that looks like a bilberry splat. Failing to learn from the experience of CRUK, they also object to the abbreviation BSA, which depending on preference is either related to blocking agents or motorcycles. At least BAAS got them on the front page of Google, even if it does sound like sheep shouting.)

Anyway, the article flagged for my attention is one by Sir John Krebs, son of the famous German biochemist Hans (of Krebs cycle fame) and a frighteningly distinguished scientist himself. Krebs, who chaired the 2007 working party of the Nuffield Council on Bioethics to produce a report on the ethics of Public Health, writes about the infamous ‘Nutt-sacking’. For those of you not up to date on the machinations of the UK Government, Professor David Nutt was chair of the independent Advisory Council on the Misuse of Drugs (ACMD), until he was sacked for, um, advising the government.

It’s not quite like that of course: the UK Government asked for advice on the classification, and thence the penalty for possession or trading, of cannabis. Based on evidence of potential and actual harm to individuals and society, the ACMD said that cannabis should remain a ‘Class C’ drug; that is possession should carry a maxium two year gaol sentence (compare with Class A drugs like LSD or heroin, carrying a seven year sentence for possession; and amphetamines, which carry a five year sentence). The UK Government ignored this expert advice and reclassified cannabis as ‘B’ (somebody should tell them about the Netherlands). The Prime Minister, even before the ACMD review, had already said that cannabis should be reclassified as ‘B’, and the then AMCD Chair, Sir Michael Rawlins asked the Prime Minister to butt out and wait for the review. When the review came around nobody should be at all surprised that the Labour Government ignored the advice (in the interests of populist policy and Nanny State-ness, no doubt). They had, after all, previously telegraphed that they had no intention of accepting the ACMD’s advice on the classification of ecstasy. As Lord Krebs says, ‘it would appear that the personal opion of the Home Secretary trumped the considered analysis of the statutory expert committee’. So, perhaps, the government should not have been surprised that Professor Nutt then publicly criticized them for ignoring advice.

They sacked him anyway. You can read some measured analysis from Bill Hanage, an epidemiologist at Imperial College, at the LabLit blog. Bill also lambasts politicians of all colours for failing to grasp that evidential science doesn’t give a hoot for policy.

Lord Krebs in ‘People & Science’ this month tells us that—however much we scientists might like to believe otherwise—independent scientific advice is, on the whole, valued in Westminster. Politicians of all parties are keen to emphasize their commitment to evidence-based policy, and in areas from infectious disease, to GMOs, to climate change, this commitment is usually fulfilled. There are over 70 expert committees providing advice and most Departments (but not, notably, the Treasury) have their own Chief Scientific Adviser. Lord Kreb’s own advice on the need to gather more evidence before deciding whether or not to cull badgers was accepted (but it would appear that didn’t make any difference in the long run—they eventually bowed to uninformed pressure from the farmers, presumably while P&S was in press); and the BSE crisis was handled on the basis of scientific evidence. He does, however, point out that it would have been better to assemble proper evidence before splashing half a billion quid on the Sure Start programme, but I guess you can’t win them all.

The latest example of politicians actually listening to scientists came just last week, when MPs from the House of Commons Science and Technology Committee said homeopathy ‘remedies’ are a waste of money, and should not be available on the NHS.

However, whether ministers will take heed of evidence that contradicts favoured policies, or apparent vote-winners, is still a matter of debate. The draft Principles on Scientific Advice published by the science minister Lord Drayson apparently emphasize the importance of independence, openness and respect for scientific evidence. But how are disputes going to be handled? And when Westminster ignores scientific advice, what recourse do we have? And surely, shouldn’t we be able to criticize elected representatives without fear of losing our jobs?

PS Prof. David Nutt is talking at the Science Media Centre on Thursday 18th March. I’d love to go but I’m going to Geek Pop The Science Sessions instead. More on that later.

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No definite link between cannabis use and suicide: our review

Posted by stevepog on 7 December, 2009

We’ve published an interesting review (aren’t they all though?) on a study that discussed the lack of association between marijuana and suicide risk, in what our reviewer Wayne Hall from the University of Queensland, Australia, described as “the largest and best controlled prospective study of the relationship to date“.

It’s a tough topic to tackle, especially in a time when celebrity deaths, marijuana usage and suicide are so closely linked by tabloid media (Marilyn Monroe being the newest revelation) and when fears that teenage brains getting destroyed by cannabis are high on the news agenda. But on the other hand, when a highly-respected scientist such as Professor David Nutt gets vilified by the government for his outspoken views on drugs policy, the media generally showed support for the sacked Professor while still being skeptical of his evidence-based comments (such as cannabis use being safer than horse riding).

Hall looked at the paper, Cannabis and suicide: longitudinal study, by Allebeck and Price at al. from Cardiff University UK, published in the British Journal of Psychiatry, which went beyond previous small cross-sectional studies to look at whether the cannabis/suicide attempt relationship took into account pre-existing suicide risk between young people who become regular cannabis users and their peers who do not.

In the study, more than 50,000 Swedish men aged 18-20 were followed up for 33 years using death registers to identify those who had died from suicide.

Hall says:

As in previous studies, self-reported cannabis use at conscription was positively related to suicide (odds ratio [OR]=1.62, 95% confidence interval [CI] 0.65-2.07) but this association was no longer significant when plausible potential confounders, such as problematic behavior during childhood, intelligence, alcohol abuse, parental psychiatric disorder, other drug use, and psychiatric diagnosis at conscription were statistically controlled for by logistic regression (OR=0.88, 95% CI 0.65-1.20).
The selection of confounders to control for did not affect the finding that the OR was no longer significant after adjustment for confounders. This study strongly suggests that the modest association observed between regular cannabis use and suicide in cross sectional studies reflects the fact that young people who are at marginally higher risk of suicide are more likely to become regular cannabis users than their peers.

And it’s the last point that is most pressing: those at a slightly higher suicide risk are more likely to become regular pot smokers, not the other way round. If you look at the citation rates on Google Scholar for “cannabis and suicide”, many academics seem to support the view that the two are  strongly linked.

Allebeck and Price’s earlier paper, published in 1990 at this study’s 15-year mark, even stated “the proportion of suicides increased sharply with the level of cannabis consumption“: their new study clarified that the “association was eliminated after adjustment for confounding” and the link was better explained by markers of psychological and behavioural problems.

No doubt long-term studies such as this will lend more weight to the Nutt debate and, if they are given adequate publicity, hopefully help to cut down on biased anti-drug journalism.

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