Why do some people act crazy using meth, chemical unbalance? And why so.

I smoke it and it’s pretty much like adhd medication to me now and I do know I have a decent tolerance but it doesn’t affect the way I talk and my mouth move and body language and the way I think like it does with some. Why do u think that happens to some and how long will they change back to normal, if they ever do. And also what about phyc meds and doing ice. Is it cause they stopped taking there meds to use because ik some meds make u sleepy escp anti and bipolar.