Meth itself doesn't make me paranoid, its the Sleep Deprevation that makes me paranoid. If I do it for 24hrs or less I don't have a problem, but if I'm going on 2,3,4 days the shadow people start to really fuck with me.
I also think that the quality of product that you do plays a part in things. Low quality stuff tends to fuck with people too much (such as paranoia, harsh come-down, violence, harsh taste, and just a shitty high IMO). I've seen it too many times, people getting sketched out too easy, turning scandalous (lying, stealing, deciete), and getting violent on cheap, dirty meth. Another negative of cheap meth is that you have to do alot to get really spun.
But on the other hand, the same people can do high quality meth (Glass/chards/ice/whatever your slang is) and be completely different people. Good meth tends to have a more pleasent total experience from soo little product. Great high, good and sometimes non-existant come-downs, and just knowing your not smoking/shooting/snorting/eating all the nasty cuts that cooks & greedy dealers put in their drugs is comforting. I have become somewhat of a meth snob lately because I won't do the cheap stuff anymore, it's just chards for me! If it doesn't melt & burn clear, have that yummy taste (if you are a glass user you know what I'm talkin about), or burns quickly in a glass pipe, I don't want it. Doing cheap dope after doing glass is a joke.
Sorry for the long post, but being under the influence of the above mentioned drug made me state my opinion on doin meth and my observations of how people react to different grades of meth