Depression is more than "I feel sad", it's a disease that causes physical changes in you and doesn't go away. We still only have really a basic understanding of what the alterations in mental make-up do to you psychologically. The man fought a long time and went through some dark shyt, just because you leave that alley and the needle behind doesn't mean it ever leaves you. You can be anybody anywhere at any time and have this issue, it's not an America or western cultural thing, just like schizophrenia has a fairly consistent 1% affliction rate globally, so does clinical depression. The man fought a battle against himself and in the end he couldn't fight anymore.
Tell your loved ones that they mean something to you, reach out, don't let people in your life feel alone.