A salient point re: the existence of different types of depression. Some cause a physical slowness (can't get out of bed), some cause anhedonia, some are the dementor type, etc.
I personally cannot get out of bed and face the world, I am suicidal at nearly all points of the day (but in a curious way; it's more I picture myself killing myself, but not in a "MUST DO THIS NOW" way. Its very odd and disconcerting). I can still experience emotions (all of them), but they are heavily skewed to the negative. I ignore the future, and focus on the past and present.
It's a shit disease.