Depression is a very strange thing.
I somewhat believe that everyone has some level of depression no matter their personality, genes, or life experiences.
For me, depression is like a festering thought, the "I wished I had never known such a thing existed" - kind of thought.
I mean, it's definitely a good thing to know that depression exists.
That way people could self consciously prevent themselves from committing actions associated with depression. But that would mean people would have to manually put effort into assessing their thoughts and actions before committing them and doing that on a daily basis would be taxing, and it is.
Oftentimes, I think that depression has placebo-like effects. If a person were to repeatedly think to themselves that they were depressed, they would actually get depressed.
To simplify, here's a quote, "it's not really there until you say it's there, but it's always there even if you do not know it's there."