Daily Mail gets confused on cannabis (again)

The Daily Mail today continues its long history of fuzzy headed cannabis news reports with a piece today entitled Cannabis warnings improve police-youth relations, Yard argues. Unfortunately what appears to be a potentially promising title (assuming we think that improved police-youth relations are a GOOD THING) immediately stumbles into statistical nonsense almost before it is out of the blocks.

We are told that it is a 'fact' that 'the "softly softly" approach is contributing to a huge rise in cannabis use.'; the data presented to support this 'fact' is that there was a 12% rise in cannabis arrests in 2005.



Let's be absolutely clear about this: arrests are NOT a measure of levels of use. There is no direct causal relationship; an increase in arrests is most likely to be the result of changes in policing policy or the intensity of policing efforts. It could be suggested that the 2004 reclassification has meant people are more open in their cannabis use and, not really understanding the new law, are being arrested more often as a result. But the Mail's analysis isn't that sophisticated, instead opting to present and entirely spurious link between arrests and prevalence as fact. Which it isn't.

A more reliable way of measuring levels of cannabis use is to ask a suitably large number of people if they use cannabis and then tot up the results - a so-called 'survey of drug use'. There are lots of these in the UK, the biggest official ones being the British Crime Survey, and one done annually by the Department of Health. They are not without methodological flaws and are generally acknowledged to underestimate the totals, but they do at least show year on year trends fairly well. If Ben Taylor of the Daily Mail had consulted the figures he would have discovered that cannabis use has actually levelled off or even (if you believe the BCS) fallen marginally since 2004. So not quite the 'huge rise' he reports.

Its not the first time the Mail have gotten all in a spin on cannabis and ended up with news story that is some distance from representing reality. Last year, under the headline 'The deadly downgrade' (blogged here) they reported that 'drug deaths spiralled after Labour downgraded cannabis' on the basis that drug deaths had increased marginally between 2003 and 2004. This whole story looks pretty ridiculous when you consider that:
- none of the deaths were cannabis related (they were almost all opiate related)
- the drug death data covered a period before reclassification occurred
- cannabis use fell marginally after 2004 anyway

There was also a another piece of hopeless news coverage (also blogged) about a campaigning Vicar (who amusingly penned the Sinitta disco smash 'So Macho' back in the 80s) who is uncritically reported blaming all sorts of terrible things on the reclassification of cannabis (not the drug itself - the actual policy change) from murder to mass insanity.

This latest report, like the various others before it, seems to be an attempt to have a go at UK drug policy and in doing so make the Government look bad. Fair enough I suppose if that's your political/editorial position, but if so then the really baffling thing about the Daily Mail's ongoing rubbish reporting and bad science in its coverage of the cannabis issue is that there's just no need for it. There is so much wrong with UK drug policy that they could be running all manner of withering coverage without having to misrepresent and twist statistics. The drug strategy has been a disaster on almost every indicator you could choose from, so it seems downright odd that the Mail repeatedly chooses to direct its ire at one of the very few bits of Government drug policy that the police can legitimately argue has been vaguely successful.