It's a meta-amphetamine variant of methamphetamine. Pre-War meat companies were experimenting with a protein extract, but the slightest contamination of the product made it act as a potent amphetamine as it was being digested. Instead of abandoning it altogether, they decided to give it to their cows. Somehow, when all the radiation mutated them into brahmin, the extract basically bonded with the cattle and became a natural byproduct of their digestive processes. As a result, all brahmin shit contains Jet.
In other words, it's basically a "super" meth that provides a significantly more intense high than regular meth. But the high also fades much, much more quickly than regular meth.
So if you want to know what Jet does to people . . . It's a more addictive form of meth that gets you into the addiction cycle much harder and faster than normal meth. So I guess just look at what meth addiction does to people and think, "It does that, but faster."
And since, again, literally all brahmin shit contains the stuff it must be a bitch and a half to fight Jet use. You'd basically have to replace all your cattle with non-mutated cows to get rid of the stuff.
