That said, the Madness rules in the DMG are abjectly terrible. They are non-integrated, incoherent rules that fight the rest of the system instead of adding to them. I mean, they add to existing things on the GM's whim, are based off of WIS and CHA saves which means that melee classes are gimped while those that dabble in the arcane are stronger against them -- an inversion of the tropes. Further, the impacts are either negligible or incapacitating, and not much between. Finally, all of the "permanent" madness effects tie into the BIFTs and are totally ignorable -- there is no teeth at all to enforce them. So, what you end up with using the Madness rules are trope inversions, effects that are either incapacitating or ignorable, and then only in the short term. And the effects that are incapacitating are all tightly tied to the combat engine.