This story is a bit frustrating and contradictory.
It states, and was widely reprinted in a number of pro-marijuana Websites, that a study from the Annals of the American Thoracic Society says that long-term marijuana smoking has no adverse effect on lung health. (However, this is where these stories drive me crazy — what the study actually said is that long-term marijuana smoking has no adverse effect on lung function. Important distinction.)
What these means is that even after 20 years, it appears for most pot smokers, the lungs still operate at the same capacity, etc., as before the smoker started using pot. That’s drastically different from cigarettes, which seriously impair lung function after a few years (Basically, smokers finding themselves easily out of breath.)
This article, which was written by someone from NORML, contradicts itself slightly by stating that long-term pot smokers “self-report” increased symptoms of bronchitis … and this is the contradiction. Bronchitis, especially chronic bronchitis, leads to more serious COPD … so taking this statement at face value, chronic pot smoking does in fact have a negative effect on lung health.
This article on the same study from ThinkProgress is a little more balanced, I think. It acknowledges that pot smokers seem to have increased bronchitis symptoms, but it blames the rolling paper for that.
There’s studies out there finding zero link between pot smoking and COPD and pot smoking and lung cancer. I don’t have a problem believing the studies on lung cancer, but I personally believe, despite the fact I can’t cite studies to back this up, that long-term chronic pot smoking is simply not good for your lungs. It might take a lot of pot for a long time to seriously damage your lungs — a lot — but it’s still smoke and constant smoke in your lungs are not going to do them any favours. Again, this is just another in a long series of exasperating articles on pot smoking and lung health.
All that being said, I absolutely believe pot should be legal. There’s no logical reason why it is illegal while tobacco and alcohol and legal. And whatever damage pot does to people physically pales by comparison to the damage that pot laws do to people’s lives.