Basic Trope: Someone learns something that is from their perspective and the context of the story, very horrible that was something secret or hidden and they end up going insane because of it.
Straight: Alice sees something, reads something, or is told something either purposely or accidentally and it makes her go off the deep end.
Downplayed: Bob learns something that, while it doesn't make him go insane, it deeply disturbs him and he may never be quite the same because of it.
Averted: Jill is not at all bothered by whatever information she uncovers in spite of how earthshaking it is.
Inverted: The truth that is revealed to Kevin not only doesn't make him go crazy, it makes him become more sane or cures his insanity.