Depression, (not the clinical kind), is the soul calling. The soul crying out.
When the soul is hungry, you get depressed.
Depression is the soul saying,"I am not satisfied".
You are not fulfilling your soul's calling. Therefore you are feeling down.
Animals do not get depressed, for they are always doing what they are supposed to be doing.
Human beings do get depressed because if you are not doing what you are supposed to be doing- your soul will cry to you.
More sensitive people are more aware of this calling.
Depression is a wake-up call from the soul saying, "I'm not happy, do something".