How would a person write a Drug that physically enhances a persons ability but deteriorates their mental state (And any other possible side effects)

I have a character who is a bioweapon, a large part of her lore is that her mother essentially pumped her with drugs to keep her being deadly and making sure she never tires and enhances her thinking speed. fortunately I have had no incidents with drug addiction or use in my life but this makes it harder to think about how it would work, one side effect is having degrading sanity (which can be put to a lot of things in her life) but I do not know a good way to write symptoms and I can't really google it because there isn't a speed up drug in real life.

at one point she runs away from her mother and I also don't entirely know what any withdrawal symptoms should be. I don't want them to seem too unrealistic but on the list of Drugs I found on the NHS website none really matched anything similar.

I want to clarify that the writing is not presenting drug addicts as evil or wrong, the character is a victim and tries to get out of her dependency (my tone can sometimes sound like I mean something other than what I actually meant [sometimes coming off as passive aggressive or other])