J.M.W. Turner, The Burning of the Houses of Parliament,1834. Turner is thought to have had bipolar disorder.
Euthymia
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.
More from ABC News here.
An earlier reference on this blog to Turner here.