I wonder if there's more high-functioning heroine addicts or meth addicts. You might assume meth off the bat, but there are some very prolific heroine junkies through history.
I think functional junkies last longer. I knew a couple fellow programmers back when, who crossed the line between recreational and need-it-to-function. They could crank out code like mad, for a while. But they eventually were fired for general unreliability and weirdness. Not sure what ever happened to them.
They're all Fine People, until receptors have been extinguished to the point of causing crippling depression without drugs.
It's not that the brain doesn't work , it still works OK if you put drugs in , but because the body no longer maintains basal levels of your brain chemistry in the same way, the person can no longer function sober.
As for, where is the cross over point.. drug use has a toll.. side-effects of medicine, (mostly from impurities).. but that aside, there's a limit of how long your body can carry on its other autonomic functions under the shifted balance.
So, eventually it's not necessarily the drug that kills you, it's the other problems which were side-effects of the drug.
As for Meth vs Heroin.. Meth is 10x as strong as heroin and lasts about 1/3 as long.
So, it causes an even larger chemical swing.. Meth is obviously the most quickly destructive as it gets you to that cross over point faster..
