Whenever you lose sanity, the marker on your sanity track advances to the right. If it reaches the skull at the end, you are consumed by madness and eliminated.

The track has Insanity Threshold () spaces that will activate your insanity and level up a skill. Some of them also give you permanent bonus dice. When an investigator loses more sanity (from dice rolls, Discovery, or Mythos cards) than required to hit the next , the marker stops at the and all excess sanity loss is ignored.

- Gaining bonus dice

4 of the spaces display a green Bonus die under them. Once each of these is reached, the investigator adds +1 Bonus die to ALL rolls they make for the rest of the game.

- Activating insanities

Each investigator gets an insanity card at the start of play. Every time their marker on the sanity track reaches a , that insanity activates. Perform the symptoms on the card. If multiple investigators reach a at the same time, they activate clockwise from the current player.

- Leveling up skills

When the marker reaches a , after activating their insanity, the investigator levels up 1 of their skills. Choose 1 skill and move its marker 1 space to the right.