That answers one question.
As to the rest, in my line of work I have seen the effects of this drug and I know that it does have at least most of those side effects : fatigue, memory problems, decreased motor capabilities, slurred speech, dizzyness. And it seems obvious that you would have lung problems, I mean you are lighting something on fire and breathing it in, that is not good for your lungs. As to the long -term medical problems, I haven't seen them firsthand but I have seen the others so it seems logical to believe that it could have other negative effects.
One other thing, think about which side would benefit more from lying to you. Cuz face it, they cant both be right, either its not harmful or it is.