Now, those are my words and they may have been a bit hyperbolic, but if so my excuse is that I'm tired of hearing it assumed marijuana is bad for you when there is no unambiguous evidence to support this proposition. I've seen numerous studies like the one you sited above but those in the past have all faded from view as subsequent studies have consistently refuted them. As a scientist, I know that it's not all that difficult to produce a study that supposedly validates whatever assumptions one wishes to prove. Scientists have no claim to moral superiority and as in any group there are those that put their knowledge to use with a bad intent. Government funding is a powerful motivator, especially when the objective is to justify political policy. I admit that I have no specific clinical studies to cite that will directly prove the assertion that you quote. My motivation here was to induce folks to provide information that would purport to disprove what I was claiming and in doing so I may have gone a little over the top in a few instances. This is more a statement reflecting my attitude and general overall impression of the accumulated research than it is a cold, hard fact, which it may well be but that's not something I'm prepared to prove right now. As far as I know, CO from combustion is the only harmful byproduct of smoking marijuana and I put this "harm" in a relatively benign context. Have you ever gotten a painful headache sitting in a freeway traffic jam? I know I have and years ago I saw a study that claimed this is caused by breathing in CO from all of the surrounding auto exhaust. I believe that this is a larger and more health impacting CO event than one would ever experience smoking marijuana, but that's just my opinion. You realize of course that I asked for proof first, and I do appreciate the link you provided although I do not find it convincing. In the future, please try not to take my words out of context.