Why Art Thou Cast Down?

If the Bible is a source of wisdom and knowledge which covers all life situations, then where does it talk about depression?

We have found three ways in which the Bible describes depression:

1. A spirit of heaviness ( Isaiah 61:3 )
2. Discouragement ( Isaiah 42:4 )
3. Cast Down ( Psalms 42:5-6, 11; 43:5 )