I agree with the chemical explanation. When you're in that dark place, you're incapable of feeling the least bit of pleasure, and you just have this agonizing sadness.
I've found the worst depression to be the type where you're depressed but still have your head above water, so to speak. You have the energy your normally have, but you carry this weight of depression around and it drives you crazy. You're angry at yourself and others and you can't figure out how to get out of this prison. The other type of depression is easier to deal with, the one where it's overwhelming and you have no energy or desire to do anything but to crawl into bed and let the sadness wrap around you like a protective blanket. Because that at least is a comfort, in a strange way.
As for suicide, my thoughts on it have changed. I used to think it was a brave act. I consider myself a bit of an artist, and the Romantic appeal of it fascinated me. But the selfishness of it unsettles me. If you know someone cares for you, whether it be a friend, family member, whoever, it's unfair to hurt them. I can see doing it if you truly have no one who would give a damn, or feel you don't, and I can see doing it if you have a terminal illness. But other then that, it's too morally objectionable for my tastes.
I've struggled with suicide temptation fairly often, but I've been fortunate in that I've never formulated a plan. I credit that to knowing I have people who care about me, and also, that my depression tends to zap my willpower, making any planing unfeasible. Plus, fear of death and whatever comes after death. It's odd. Even when I don't have anything that gives me pleasure and sleep a lot, I still don't want things to just end permanently. I like the idea that life always has the potential to get better. Maybe I AM an optimist, ha ha.
Anyway, I'm inclined to think that you have to be hardwired a certain way to not only find suicide appealing, but to go through with it. Many people experience terrible sadness and hopelessness for long periods of time, and never kill themselves. I wonder what exactly is the dividing line between them and those who do choose to end their lives?
Fascinating subject.
