Does smoking weed really result in brain abnormalities? Maybe not.

554px-Cannabis_leaf_2.svgA study purporting to find that marijuana use (even casual marijuana use) may be associated with brain abnormalities has been getting a lot of press lately. You can check out some of the coverage at CNN Health, the Huffington Post, and Fox News. And you can check out the original paper in the Journal of Neuroscience, Cannabis use is quantitatively associated with nucleus accumbens and amygdala abnormalities in young adult recreational users by Gilman et al., here.

Shortly after the study came out, Lior Pachter posted an analysis of some major problems with the study on his blog. I’m posting a link to his post because I think it’s a great example of something science bloggers do very well: they share important information about the quality of recent studies in real time. This is essential stuff you just don’t typically see in media coverage.

I’d also like to note that the statistical issues he points out are very basic ones. Adjusting p-values for multiple testing is something that I think most researchers understand they have to do even after an introductory stats class. So I’m having a difficult time understanding how this manuscript sailed through peer review in its present form. The Journal of Neuroscience is not some fly-by-night journal! I hope that journal editors will see what happened here and realize that if a manuscript contains statistics, it’s probably a good idea to choose at least one reviewer with knowledge of statistics. Failure to control for multiple testing appropriately is something I see over and over again in the articles I review. There is definitely a need for the statistics police in the peer review process.

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