I did a review of the literature on the harmful or beneficial health effects of marijuana several years ago and didn't find any convincing (non-marginal-result,

I did a review of the literature on the harmful or beneficial health effects of marijuana several years ago and didn't find any convincing (non-marginal-result, controlled) studies that showed marijuana had long term negative effects on health. The literature I find is pretty weak. Not only are these studies weak, but there are even mixed results - some (similarly unconvincing) studies suggest marijuana has positive health effects (anticarcinogenic, etc). This study is in line with what I found. I find it plausible (and rather obvious) that marijuana use causes short-term negative effects. I'm more interested in the long term effects, though. I take it for granted that marijuana use is going to have negative cognitive effects in the short term (e.g. the next week).