You could maybe say this if you accept that: A) personality and emotions are standard human brain function and B) extreme and atypical examples of A) generally stem from genetic predisposition, hormone imbalance or underdevelopment of the certain cognitive functions due to environment (past or present).

>So mental illness is just "personality and emotions?"

Didn't say that. "Behavior," taken as a whole--from simple to complex life--paints with a really broad brush. Emotion and personality are very individualized. They count, of course, and this would be the (jurisdiction) of psychology. (Doesn't this patch belong to psychology? Don't psychologists deal with personality and emotions?