It depends whether you mean clinical depression or sadness/melancholy.
And if you are looking for a scientific/medical explanation, a Buddhist explanation, a combination or something else.
There is a vast amount of literature on clinical depression in medicine. Its a very well understood condition.
“No lists of things to be done. The day providential to itself. The hour. There is no later. This is later. All things of grace and beauty such that one holds them to one's heart have a common provenance in pain. Their birth in grief and ashes.”
- Cormac McCarthy, The Road
Learn this from the waters:
in mountain clefts and chasms,
loud gush the streamlets,
but great rivers flow silently.
- Sutta Nipata 3.725
(Buddhist aid in Myanmar) • •
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