I have only experienced regular smokers' trouble such as coughing, wheezing, aggravated asthma, and congestion as a result, but that always stopped within a short while of ceasing to smoke cannabis.

I don't know of anyone here on the boards who's had lung cancer as a result. But I do know two gentleman, one of whom just died about a week ago at 63 in the hospital in my hometown, who were longtime, heavy, heavy cannabis smokers and developed a form of large-cell lung cancer (a slightly different variety than typical cigarette smokers' cancers). Neither of these guys had ever used cigs, but they were absolute chimneys when it came to weed. Heavy, multiple daily use over decades. The gentleman who is still alive, who's 52, is lucky that his cancer was caught a good bit earlier and has a better chance of surviving his cancer. Both are/were at various times dealers and had access to enough weed to be able to smoke it in the same volume as most heavy cigarette users.

Can anyone say that their cancers were for sure caused by cannabis? No, no one ever can. But considering that neither of them were cigarette users and that the big difference between their pulmonary history and that of nonsmokers was heavy lifelong weed use, it's a relatively easy conclusion to make. You have to take into account that they might also have been sensitive or likely to have gotten lung cancer anyway, just like someone like Christopher Reeve's wife Dana, who got it without explanation.

I'm going to see if I can encourage their pulmonary docs to send their information and histories to Dr. Donald Tashkin at UCLA and see if he had any other case reports like theirs among his research. We expect that he does, but he may also see something there in the pathology/morphology details that will explain their cancers better. Tashkin himself knows and mentions in his low-link-between-MJ-and-lung-cancer studies that there does seem to be evidence that longtime MJ use can put into motion some DNA changes. He's in the process of studying that now.