The web is oozing sweet, sad messages about listening to your depressed person, being there, sticking by them... But even though that all sounds good and true, it could make the self-hating depressed person feel even shittier. Now with you glued sympathetically to his side, he's not just a turd on toast, but a pitiful, unworthy, pain-in-the-ass, turd on toast, bringing you down with him.
When I cracked up several years ago, I remember the burden of sympathy made me feel even more guilty and worthless. And I really, really, really didn't want to be beholden on top of everything else. I wanted to be invisible.
Also, knowing how lucky I was made it all more humiliating. There were people out there who were making a brave go of it with a lot less than I had... and yet I was the wimpery, self-pitying asshole curled up in the dark...
Counting one's blessings and knowing people are worried about you can magnify the self loathing and just make you feel crappier.
I'm not saying we should all ignore depressed people, but just as sympathy would not cure a bladder infection, it won't cure mental illness/depression.
It may leave the survivor feeling less guilty, and in hind sight it may make the sufferer grateful that you stood by, and those are good things. Plus we've all got to do whatever makes it easier to live with ourselves and others.
But we can't assume that those who succumb to depression lacked for sympathetic comrades, or a clear accounting of their blessings.
It's not that simple. Depression is an illness and needs a cure.
Better living through better chemistry.