Watch those marijuana studies

The fine folks at Slate helpfully weigh in on a recent study that purports to show a link between smoking marijuana and gum disease. Apparently - and this may come as a shock - there were problems with the study's design:

First of all, the absence of information about daily dental hygiene and—much more significantly—other drug use is a serious flaw in the study's design. Cocaine and methamphetamine use are both highly associated with periodontal disease.

Of course, there's been a small flood of "weed is bad for you" stories lately... the fine folks over at the Slog, for instance, recently took a closer look at that study that seemed to show that quitting marijuana would cause bad withdrawal symptoms. The problem with that study:

Everyone [in the study] smoked both pot and cigarettes. The good of this: the effect of withdrawal could be compared between pot and tobacco in the same individuals. The bad: it’s already known that pot and tobacco interact. Perhaps the severe withdrawal seen after stopping pot in this study has more do with the effect smoking pot had on how nicotine was processed in the brain.

There's clearly a lot more to be said about this type of study, but I am waiting for smarter people to post about the topic...