June 8, 2019:
It can be difficult sometimes to distinguish in my own experience between sadness and depression.
Some event occurs, some setback, say the withering away of a friendship once full of promise. It's natural to be sad. Someone you care about is gone, there's a lonely space in your days and your heart. Yet the setback and the loneliness trigger something more, a deeper darkness potentially without limit, like a trapdoor opening onto an ugly infinity.
Are you sad? Are you depressed? Would your feelings be different if your brain chemistry worked?