There is a few things to add. There is still a lot of research to be done. I'll take a few example from the article you posted and other studies.
The main study in the article was this:
http://www.ncbi.nlm.nih.gov/pubmed/25521349
They concluded: "
In a large cross-section of U.S. adults, cumulative lifetime marijuana use, up to 20 joint-years, is not associated with adverse changes in spirometric measures of lung health. Although greater than 20 joint-years of cumulative marijuana exposure was associated with a twofold increased odds of a FEV1/FVC less than 70%, this was the result of an increase in FVC, rather than a disproportional decrease in FEV1 as is typically associated with obstructive lung diseases."
Might seem like gibberish, but basicly obstructive lung disease is usually characterised by a FEV1/FVC ratio less than 0.7, or 70%. They claim that it was because an increase in FVC, but even then it's questionable. The study also don't mention the amount of people participating, and it was probably genpop. When I used to smoke, I smoked 2-4 joints a day easily. Which leads to this:
"
This association, however, was nonlinear: at higher exposure levels, we found a leveling off or even a reversal in this association, especially for FEV1. Although our sample contained insufficient numbers of heavy users to confirm a detrimental effect of very heavy marijuana use on pulmonary function, our findings suggest this possibility."
In this other study linked in the article, it says:
http://norml.org/news/2013/07/11/st...d-with-far-fewer-adverse-effects-than-tobacco
"
His review finds that although smoking cannabis may be associated with symptoms of chronic bronchitis, studies do not substantiate claims that it is positively associated with the development of lung cancer, chronic obstructive pulmonary disease (COPD), emphysema, or bullous lung disease."
Again, symptoms of chronic bronchitis. He also noted:
"
That “evidence is mixed” when it comes to the carcinogenic properties of heavy, long-term use. He also notes that heavy smoking has been linked to a reduction in the amount of tiny hairs in the bronchial tubes, called cilia, which filter the air going to the lungs, as well as a loss in the antibacterial functions of the white blood cells present on the lungs’ alveoli — the tiny tree-like balloon structures that form the boundary between the airway and the blood stream."
In these studies:
http://www.ncbi.nlm.nih.gov/pubmed/24384575
http://www.ncbi.nlm.nih.gov/pubmed/21859273
http://www.ncbi.nlm.nih.gov/pubmed/26836917
There seem to be a clear link between smoking weed and inflammatory airways/bronchitis. Even some worse associations.
It also has a lot to do with HOW you smoke and how much you smoke. Here in Europe, we use tobacco and hasish (condensed oiled form) together in one joint. Apparently that's even worse than doing each thing seperately:
http://www.ncbi.nlm.nih.gov/pubmed/23664286
So, a lot of things to take into consideration. No doubt vaping is as good as it gets, and
no doubt that it's a lot better than smoking tobacco. Dosage again is important. If you smoked 20 joints pr day as most cigarette smokers do tobacco , you would probably not feel to well.