Suggestions for Best Sanity System?

Starting a new campaign in which the concept of sanity is an important part of game play, but I don't see any DnD rules for it.

I recall that Call of Cthulhu had sanity rules, which were something like hit points for sanity.

I was also considering adapting the exhaustion rules for mental health a.k.a. sanity.

Has anyone had a good experience using sanity in their DnD games? If so, what did you use?