Are there any mechanics for tracking sanity or performing sanity checks?

Question

I am playing DnD since 3e and recently my fellas and I bought the 5e books. I already DM them in some eldritch-horror style campaigns.

Back in the days of 3 and 3.5, characters used to have sanity points and a system that allowed them to roll a d% to see if they pass or fail a sanity check. This would result in players potentially losing sanity points.

With 5e, I cannot understand how someone can go mad, crazy, etc since there is no sanity point system.

So do I just roleplay their way into madness without keeping track of who's actually close to being mad, crazy, etc or am I missing something?

Thank you in advance for your replies.

Answer 1

There are optional rules that add sanity as an ability score. They can be found in the DMG on pages 264-5. The rules for madness start on page 258 and define short-term, long-term and indefinite madnesses you can impose on the players. The rules for fear and horror on page 266 might also interest you.

Answer 2

Another option using standard Conditions and Mechanics

If you don't want to use the Optional Sanity score in the DMG as suggested by Szega and Kviiri, you still have access to some options in the PHB that you could tailor to your game.

Frightened

Fear is a big portion of the horror setting, and you could utilize Wisdom checks for the Frightened condition. It doesn't have any variance in level of fright, but that's where you could introduce Exhaustion mechanics.

Exhaustion

For any given number of hours/days/weeks that someone remains Frightened, they could suffer another level of exhaustion due to their state of Fright. This provides a means to add a mechanic beyond the Frightened Condition, and also allow for spells like Greater Restoration to help them get over it and mitigate their plight of fright.

Answer 3

Variant sanity rules in the DMG

Dungeon Master's Guide has optional rules for sanity checks, on pages 265 and 266. The rule is that Sanity is a new ability score (along with Strength, Dexterity, etc) and actions taxing the character's sanity are resolved by a Sanity saving throw.

A failed Sanity saving throw results in a semi-permanent loss of a single point of Sanity and suffering a mental illness described in DMG chapter 8.

Answer 4

The Out of the Abyss module (spoiler below)

made frequent use of a system for madness rolls and saves, since the characters face a lot of demons. By that point, though, the various insanities contracted are too easily cured through Greater Restoration or other magics.

That's probably the closest you'll get from official sources, although for a campaign that features real threats to the sanity of the characters, I think you'd still need to homebrew something a lot more detailed.