Not entirely within context, but a “Mental Health” stat could be nice. It could act much like the the hidden health stat does now, with the risk of gaining penalties and diseases if it’s too low, and it could even adversely effect physical health if it get’s out of hand (body is a plaything of the mind, and all that). The obvious way to have this stat incremented/decremented is through morale.
Anyway, more directly to the OP, not everyone would care too greatly about lacking any contact with others, and at the same time there are others which crave attention to unhealthy degrees. So at the least, we should have a traits which reflect those things as such. Can’t really comment on how serious prolonged isolation could be, and thus how it should be reflected in game, so I’ll leave it at that.