I have also been depressed for a significant fraction of my life, a period that spanned over two decades. In my case it was primarily caused by what was called

I have also been depressed for a significant fraction of my life, a period that spanned over two decades. In my case it was primarily caused by what was called "anxiety" until recently and is now generally called a "stress disorder," but for most of that period the stress disorder was entirely cryptic; I had no idea that I was a particularly 'anxious' or fearful person. I can tell you that my condition eventually responded dramatically to medication, and that I would not be able to live the life I live now if it were not for that medication; furthermore, that because of the medication and my experience during the years I have been on it, I can look forwards to continuing to reduce my dependence on that medication. Depression is indeed a normal response to ongoing helplessness and despair. I probably share your experience of depression in this regard, because the 'depression' that I had been treated for for years was suddenly completely irrelevant the moment my brain finally responded to medication. However, there are several things that this account leaves out. You can't scoff and say that depression is just an normal response any more than people can scoff and say the reason you don't want to take a shower is because you're lazy. For one, as you know, depression can be very self-perpetuating. People come to believe things that keep them depressed, ruminating on their depressed state over and over again. People always see verification and never contradiction of their worldview, even though the entire world has somehow failed to just lay down and die over the course of many thousands of years, which is what it would do if that understanding of reality was valid. And people very definitely do encounter depression that does not have a proximate external cause to justify the response; many of those Afghanis, for instance, will suffer from the bleakest of depressions for many years after the wars in Afghanistan are ended. All of these things constitute a medical condition. If you don't like the word "illness" because of how it makes you feel, I can sympathize. But that doesn't invalidate the fact that depression is something that frequently does become a genuine medical problem and frequently does require a solution beyond the reach of the person suffering from it.