Do you know what the symptoms are of those who abuse for a while. I'm curious. How is the brain damage manifested behaviorally?
More physical damage than brain damage, I would think. Not really a psychoactive drug. It's speed. It increases your heart rate something fierce. Makes you want to stay up all night and party. You can drink gallons of beer, and not even think of sleeping. Any mental effect would come from plain ol' lack of sleep.
It's kind of like nicotine, in that it's so addictive because there's no hallucinations and "seems benign". Then they wake up 10 yrs down the road looking 30 yrs older and wondering why their life is a shambles. Saw it happen to a couple friends, many years ago.