Hmm... no, I'm pretty sure the psychotic meth people are psychotic due to their long term addictive use. And using really potent versions, and smoking it to get it right into the bloodstream, over time their pleasure centers are just plain burnt out and paranoia sets in.
My friend was a careful user, very smart, studying bio, and still wound up addicted. But he may have been grounded enough and focused enough not to take so much he went over the line to that level.
The History section on Wikipedia is very interesting. For a long long time they didn't even know its adverse effects and it was available over-the-counter.