Cannabis: Time for some science

I've mentioned before that I like the cut of Ben Goldacre's jib. He is a medical doctor who writes the "Bad Science" column in the Guardian on Saturdays. He recently won the Royal Statistical Society's inaugural award for statistical excellence in journalism. He has a blog, also called "Bad Science".

Last time I sang his praises, it was for debunking the President of The Gambia's claims to cure Aids/HIV in a day. That was a bit of an open goal.

This week, Ben Goldacre takes aim at recent claims about cannabis:

1. The Daily Mail headline: "Smoking just one cannabis joint raises danger of mental illness by 40%". In fact, when you strip down this claim, as Ben Goldacre does, it boils down to: "about 800 yearly cases of schizophrenia are attributable to cannabis." A serious problem, but somewhat different from one joint causing an increase in mental illness of 40%.

2. The recent debate has tended to make the assumption "that reclassifying cannabis will stop six million people smoking it and eradicate these 800 extra cases of psychosis.":

If anything, for all drugs, increased prohibition may create market conditions where more concentrated and dangerous forms are more commercially viable. We're talking about communities, and markets, with people in them, after all: not molecules and neuroreceptors.

Ah nostalgia! That reminds me of a LibDem conference debate, several years ago, when we voted to have a Royal Commission on the topic, but were portrayed as wanting to force two week old babies to smoke cannabis (or something like that).

3. Modern cannabis "is 25 times stronger" than in the 70s. This was a claim started in the Independent on 18th March in an article entitled: "Cannabis - An Apology". Ben Goldacre's "Bad Science" article entitled "Reefer Badness" pulls this claim apart:

To get their scare figure, The Independent have compared the worst cannabis from the past with the best cannabis of today. But you could have cooked the books in exactly the same way 30 years ago if you’d wanted: in 1975 the weakest herbal cannabis analysed was 0.2%; in 1978 the strongest herbal cannabis was 12%. Oh my god: in just 3 years herbal cannabis has become 60 times stronger.