I've heard of many docs say that some of their patients do pot, and its beneficial to their health. Of course doctors aren't going to say "yes pot is great for you.". But I suppose it is something to consider. I did pot for a number of years when I was younger, and my PFTs never lowered, I had hardly any exacerbations as well. I'm not saying pot is great for your health, but it never had an effect on me in my younger days. My PFTs while doing pot hovered between 100% to the low 90s. Its only recently that my PFTs have gone down, and that's due to a multitude of reasons other then pot.