Oh my dear lord, you guys are relentless in your stupidity. Please tell me what, as it pertains to my previous statements, in this article should make me weep? For the last time, I am generally positive towards weed, I am merely stressing that it is unequivocally scientifically proven that THC, the active ingredient in weed, has both short and long term side effects. Curiously enough you yourself provided me with a source to quote, and i quote from the above posted article: "
In the near term, smoking marijuana irritates the airways and can cause coughing, and public health advocates stress that it causes impairment that reduces attention, lowers motivation and heightens the risk of accidents. Over days or weeks, chronic use can 
lead to problems with learning and memory. But whether smoking marijuana sets off the type of pulmonary changes that lead to lasting damage like chronic obstructive pulmonary disease, a leading cause of death among Americans, was not entirely clear."
The fact that smoking moderate amounts of weed, which is not the fact for all weed smokers, does not seem to cause pulmonary damage is news to me, but as i stated above, weed still have well proven side effects. Another thing to remember while putting this study in perspective, is that many smokers smoke a lot more than one joint a day, and that the study concludes that "Dr. Kertesz noted that with heavier marijuana use, described as 10 joint-years of exposure or more, lung function did begin to decline".
 I  will therefore conclude, using an article you posted, that weed indeed does have side effects, and that smoking weed indeed can cause pulmonary damage. Thank you for helping to prove my point, I guess I have been to lazy to find my own sources, but with people in here being so helpful in finding sources, I guess i got lucky.