In my experience, (Score 4, Informative)

people with depression, even deep depression, can smile, laugh, and be outgoing right up until the moment they commit suicide.

It's part of the syndrome that they want to act like a natural, happy person, even if they're on a brink - no matter what. Many won't admit they're ill until fatal results happen.

Insurance companies shouldn't have anything to do with diagnosis, they aren't qualified (not being doctors), and they have a conflict of interest, making money by denying illness. Frankly I think making money by denying health care to people is nearly as unethical as just shooting them up front.