I am an occasional drug user
I am 68 years old. In excellent physical condition, and very fit looking, still have abs. The younger doctors at Kaiser say continue with whatever you are doing, and the old doctors dislike me because I don't need to take the drugs they do.
A good book to read is "Licit & Illicit Drugs by Consumer Reports, published in 1972, It was an attempt to provide a rational analysis of drug use and users.
It is hard to get any good scientific studies done on any drug that is a generic or considered a non-virtuous drug, often the two go together as no money can be made on generics. Meth certainly falls into this category. IF ANYONE KNOWS OF ANY GOOD STUDIES ON METH. LET ME KNOW, in English or German.
I've never abused drugs, and occasionally use meth, take one booty bump, the most efficient way to take it, and that's it. I can keep it forever until I want to use it again. I volunteer at a halfway house so see a lot of abuse of everything, alcohol being the most frequently abused. A biotech engineer friend, I'm electrical, says the industry is working on a modification of methamphetamine to make it a libido enhancer. When I was a paper boy in rural Iowa, most of the older people took a little white pill every day, complaining that their day just didn't go right it they didn't take it. Most of them lived well into there 80's even 90's. The US Air Force uses amphetamines and allow pilots to fly multimillion dollar planes, and were used in Iraq, that is why, though controlled as they should be, are allowed in the US.