Doesn't it? Replace the word "mind" with "body" and it seems like the very definition of disease.
By that argument, if you're grieving the loss of a loved one, deciding whether to marry, struggling to write a novel, or even fixing a bug in a computer program, you have a disease. All those presumably have some biochemical correlate.
"Everything in the mind is biologically mediated"
Proof of that?
No proof, but I meant an implicit "even if you assume that" at the start of the comment.