Thanks for the links Wing-Zero.
Both of those studies come from the same data set based on surveys, given by the government, National Health and Nutrition Examination Survey. People tend to lie on surveys. Surveys can also be written in such a manner as to produce the "right answer". Without knowing the actual questions, I can't say for sure how well done this survey was. Both of those studies also admit that 77% of pot smokers are cigarette smokers. Don't you think that kinda affects the data? We know what cigarettes do.
The government has been trying to demonize pot for years, I'm sure this is another example. They claim that through some magic of math they "controlled" out the 77% of cigarette smokers. I say, they kept them in intentionally to screw up the data and make pot look bad. In the Yale study, the National Cancer Institute was involve. The cancer industry has a need to demonize pot too. Real studies and real life testimonies actually say the opposite. There is likely something in THC that not only helps to cure cancer but also prevent it. But, the NCI can't have that, there is too much money to be had in the cancer industry.
Yale Study: http://www.yaledailynews.com/articles/v ... ?badlink=1
If you can find any legitimate research on pot, let me know. I'll warn you, it is very difficult to find legit cancer studies in the US. Unless a big pharma co, or the government is actively involved, it is close to impossible for a school to study marijuana. They can get heroin, crack, coke, etc. easily to study...but pot...no way. The government is scared of us finding out that they're lying about it, IMO.
Oh, and most of the studies the government has conducted, that I've read, are flawed. You can tell the flaws when you read their methodology.