When you make and drink potions, the effects occur. Or at least in theory it should work like that. Effects are chosen randomly, but ingredients go into consideration. "I'm going insane" is the one where you hallucinate ingedients and items on the ground. Really needed a hud to tell you about your current effects... BUT I GUESS IT'S MORE FUN TO FIND OUT BY YOURSELF!
A lot of ingredients will make potions stronger and crushing them in the mortar will increate their quality (Better effects)