Mental Health is Razputin Aquato's current health. If it reaches zero he loses a Projection Layer and respawns at the last checkpoint he activated if he has any layers left. If he has no more layers he gets kicked out into the real world, or if he was already in the real world he is transported to a different location, even though he was not in a mental world losing all of his projection layers will still cause him to be teleported to a different location.
Razputin starts out with 12 units of mental health, marked by three brain icons displayed above the projection layer display. The maximum amount of health Razputin can have can be increased by completing certain tasks in mental worlds, which will increase it by 4, marked as adding an extra brain icon on the health display. Smashing Jarred Brains and collecting them will also increase his maximum health, though not as much as completing mental worlds, as it only increases it by one unit, marked as a quarter of a brain icon. The maximum amount of health Razputin can possibly have is 72 units or eighteen brain icons on the display.
Razputin can restore his mental health by collecting Positive Mental Health powerups scattered by destroying objects in Psychonauts, restoring two units of Razputin's health (marked by a half of a brain icon being restored) if he is not at full health. He can also restore health by using items such as Dream Fluff purchased from Ford Cruller which restores all of his health, or Bird Roast Dinner or Squirrel Roast Dinner created by scorching a bird or squirrel with Pyrokinesis respectively. Dream Fluff automatically activates if Razputin runs out of Mental Health if he has any Dream Fluff.