New cannabis and psychosis study

I was asked this morning by a Comment is Free editor to write a response to the hot-off-the-press study on cannabis use and psychosis published in The Lancet, and reported across the front pages this morning.

Without having first read the paper, no way I was prepared to comment on it. I therefore recommended that Ben Goldacre or another medical expert be asked to deal with it. At least they can speed read medical research papers and make sense of them easily. Being an ignorant physicist I struggle with this stuff.

Anyway, Goldacre has taken up the challenge, and the Guardian has made the paper available on its website. On his website, Goldacre also links to the paper, and makes a snotty remark about old school media and publication embargoes. Keep an eye on Comment is Free later today for Goldacre’s take on the new research.

Update: Goldacre’s piece is published as a “Bad Science” column in Saturday’s Grauniad. A father’s reflection on the latest news by Horatio Clare was published on Friday in Comment is Free.

As for Goldacre, the sometime physician makes a few good points about the study. I’ve now had a look at the Lancet paper, and it is as Goldacre says a meta-analysis rather than a new piece of research. But a meta-analysis of the bitty research of cannabis and mental health is called for, and the authors have, from what I can see, done a pretty good job of it.

The problem with such an analysis is the way it will inevitably be used by those not trained in the art of digesting meta-analyses. That is, in political terms it can be all things to all readers, caveats will be ignored (what’s a “caveat”?), and we’ve already seen how the Daily Mail twisted the study’s findings.

Anyway, do read Goldacre’s article; it’s probably the most intelligent comment on the study so far.