Depression

According to urban wisdom (i.e. a bunch of people I know have commented on this), intelligent people are more prone to depression. Why? Who knows, really. Maybe they have the wherewithal to see things more realistically, instead of believing in the happy haze that assures us that everything works out for the best, the good guys always win, and that happily ever after really happens.

What I want to know is, if they're so intelligent, why don't they a) see that changing the way they think and essentially becoming mentally healthy is in their interest; or b) end it all quickly and painlessly, so as not to prolong exposure to the unchangeable shitpile that is life?

Maybe it's the intelligent people of above average intelligence, but below extreme intelligence/perseverance/self-discipline.

Or maybe it's something other people say to make depressed people feel better about themselves and hopefully snap them out of their funk. Though if they were really intelligent, surely they'd have enough insight to see through such a pathetic ruse?

And I could go on.