They could be very mentally unstable.
Well, there is this thing called
Personality Disorder, it's not specific, but it's close. Mine specifically is rapid emotion changes. Like at one point your sad then one point your happy. Then at one point your mad, then one you feel like laughing, ext.
PS: I find this sort of funny. I haven't even posted once in the last three pages. Like several others started arguing with others. Sort of funny...