You kinda contradicted yourself slightly there with the Coffee requiring more processing because you literally compared Cannabis being naturally occurring to Coffee being naturally occurring.

The lines of "natural" are very blurred right now, but whatever way you look at it, Cannabis, Opium, tobacco and the caffeine in coffee are all naturally occurring. Opium really doesn't require much processing as it has been used for thousands of years - way before chemical processing and refining existed. You can also take a tobacco leaf, hang it, dry it and smoke it straight away and it's pretty clear how harmful tobacco can be.

Some naturally growing plants are extremely toxic just to eat raw straight from the plant, which is as natural as you can get. So really, my point stands: just because something is natural, it doesn't mean it's healthy.

With that said I'm not against the consumption of Cannabis. My step father smokes it because it helps with the pain from his osteoarthritis but doesn't hhave a long lasting crappy feeling like the other stuff the doctor gave him. As for myself, I used to smoke it every day. But there have been too few studies and too few controlled trials to vouch 100% on the efficacy of the treatment of mental illness. Epilepsy we know is very well treated by Cannabis which is why a new drug containing Cannabis has been doing well in trials here in the UK for treating epilepsy.