Mood
Put simply, a colonist's mood is the sum total of the effects of their thoughts and traits. If a colonist's mood dips below the mental break threshold, then they will have a mental breakdown.
Colonists have a base mood of 50%, and a base mental break threshold of 10%; a colonist's traits may permanently alter their mood, or even their mental break threshold.
Mental Breakdowns
A mental breakdown occurs when a colonist's negative thoughts outweigh their positive thoughts enough to push their overall mood below the threshold.
This will result in the colonist entering one of three states:
Given Up And Leaving
A colonist who gives up will head for the edge of the map, never to be seen again should they reach it. These colonists can be reeducated and return to the colony, but only if they are apprehended before leaving.
Dazed And Wandering
Colonists who become dazed will simply wander the map until they starve to death, or are killed by hostile forces. Dazed colonists can also be reeducated.
Psychotic Rampage
When a colonist goes on a psychotic rampage, they become a danger to themselves and anyone nearby. They will attack the nearest living creature until they are either subdued or killed. Due to the risk of death or permanent injury for both the psychotic colonist and any that happen to be nearby, a psychotic colonist is a very real threat, and should be dealt with as swiftly as possible.
Once they are subdued, psychotic colonists do not require reeducation, but it may be necessary to provide counselling, depending on the cause of their mental break, in order to prevent it happening again immediately after they regain consciousness.