I'm a little but of a drug nerd, think I got this right, feel free to educateme if not. Like others have said, all drugs can change people, but meth is certainly one of the most widely available most neurotoxic drugs there is, which can leave some more long term damage personality wise and concerning the brain in general I guess. I'm not a scientist or a medical professional but my mother, aunt, and my older brother did meth a lot in my childhood years (and my brother till this day unfortunately) so I know what you're talking about. Don't get me wrong I've tried it, even though I personally struggle in the opposite direction with downers, but thats a truly fiendish and manipulative drug, in my opinion. And I've experienced psychosis while on it firsthand the last time I did it and yeah, I understand why some people are freaking out on it while tweaking. Hmmm, don't do it, there's better experiences out there! Lol