What is the science behind chems?

Chems have always interested many as far as fallout lore goes. A mirror to real life drugs that ranges from saving a life to addiction exists in the games.

Now, completely understanding it is a video game, and not every detail is going to be accurate or even depicted, what was the science behind what these chems do to the body?

Chems seem to be miraculous, stimpacks can literally save you from broken legs and gunshot wounds within seconds. Given the state of how extreme things are as far as powering things (nuclear reactors and batteries and such), do you think the same progression applied to medical technology as well?

We picked apart things like what fusion cores actually are, how Nuka Quantum glows without being dangerous to consume, and many things like that all from clues and references throughout the wastes. Did we ever get any kind of explanation as to how these chems gave people nearly superhuman abilities at times?

And this question is straight out of left field, but a genuine one at that. Marijuana...does it exist in FO or has it been referenced before? Nearly all other chems seem to refer to real life drugs; stimpacks/adrenaline, mentats/adderal, jet/meth, med-x/morphine....all up for interpretation but marijuana seems to be missing.

I find it also rather interesting that marijuana is not quite “mirrored” like other drugs are in the Fallout Universe. This could be due to the era effect of fallout. Around the 50s, much of where Fallout gets its inspiration from, “Refer Madness” and the whole campaign against marijuana was still a huge deal. It just wasn’t accepted like it is today. Could that be something that was left out intentionally due to the time? I mean, the devs don’t shy away from hard drug or alcohol use at all. They even have whole character arcs that revolve around sobering someone up, along with skills that involve being wasted that actually benefit you for being a party animal.

It could just be reduced to the fact that most plant life died off after the bombs. So there’s that.

Anyways, TL;DR:

1) Do we know the science behind chems in Fallout? Or what they are made of?

2) Does marijuana even exist in Fallout, or a “chem” version of it?

EDIT: grammar.