alt Hacker NewsA good question, but we don't know what anti-depressants do or how they do it, same with anti-psychotics, mood stabilizers, psychedelics, etc. I think we can say we have good theories for creatine.
We do know that it does do something at certain doses.
There are lots of studies. It's possible to find satisfactory information. Creatine has been studied for a very long time.
First hand experience for many is a noticeable improvement, especially during busy/sleep minimizing times, to the point where it can sometimes be a substitute for caffiene without the crash.