<unk> is a word used for indicating a normal non-depressed, reasonably positive mood. It is distinguished from euphoria, which refers to an extreme of happiness, and dysthymia, which refers to a depressed mood.
The term is also sometimes used referring to the neutral mood (absence of a depressive or manic cycle) that some people with bipolar disorder experience with varying frequency.
Euthymia 
Dysthymia
Cyclothymia
Atypical depression
Panic disorder
Bipolar disorder
Disruptive mood dysregulation disorder
Tic disorder