Poetry as a mental illness.
Interesting proposition.

Poets do not see like others.
Poets do not feel like others.
Often, they do not live like others.
Ergo: Poets are not like others.

Assuming others are normal
(assuming that normal exists)
then poets are not normal.

Does that make poetry a mental illness?

I haven't a clue and the mad-hatter
is throwing a party for which
I cannot be late. Forget normal.
Come along. We shall take tea
and play croquet with
flamingoes and hedgehogs,
while speaking in puzzles and rhymes.

That feels normal enough to me.
   ~mce