Depression reveals itself in two major forms - Reactive and Endogenous. Reactive is when feelings run the gamut between emotional sadness triggered by a minor event to great sadness at the loss of someone close to you. The type known as Endogenous is one that continues with no seeming reason for feeling this way. Sometimes an imbalance in chemicals causes this condition.
The physical symptoms of depression include sadness, emptiness, withdrawal from others, irritability, emotional sensitivity, low motivation and self-esteem, and suicidal thoughts (to name a few).
There is yet another form of depression which is spiritual in nature. Existing as a state of mind, it can come to people when God seems far away or not listening to them. In this state of mind they have lost their zeal for God and the Bible. They seem to grow spiritually tired of doing good to others (Galatians 6:9, 2Thessalonians 3:13) and ready to give up under the weight of their feelings.
There are cases in the Bible where spiritual depression seems to have occurred. King David often found himself in this state of mind and in need of God, such as when he wrote the following in Psalm 42.
Why are you cast down, O my soul, and moan within me? Hope in God, for I shall yet praise Him for the salvation of His countenance. O my God, my soul is cast down within me; therefore I will remember You from the land of Jordan, and of the Hermons from mount Mizar. Deep calls unto deep at the noise of Your waterfalls; all Your waves and Your billows have gone over me (Psalm 42: 5 - 7, HBFV).
The spiritual depression seems too much for David to bear. There is also the example of Elijah the prophet. God through Elijah had a monumental victory over the 450 pagan priests of Baal at Mount Carmel (1Kings 19). All the false prophets were killed and Israel's heart turned back to worshipping the true God.
Jezebel, the wife of King Ahab, heard what happened at Carmel and sent word to Elijah that she would make sure he would be dead within a day. When he heard the threat, even after the awesome miracle of Carmel, Elijah decided to run for his life! Traveling to Mount Horeb he laments to God in a state of spiritual depression.
But he himself (Elijah) went a day’s journey into the wilderness, and came and sat down under a broom tree. And he prayed that he might DIE, and said, 'It is enough! Now, Lord, take my life, for I am no better than my fathers!' (1Kings 19:4)
Elijah also laments that he is the only true prophet left alive. God's "cure" for his spiritual malaise was to get him busy again doing His will. He was also told that he was NOT the only righteous man left in Israel!
There is also the well-known case of Judas Iscariot. After betraying Jesus to those who hated him he had a dramatic change of heart. The remorse and depression he experienced spiritually was so severe that it drove him to commit the ultimate expression of self-hate. He committed suicide.
A possible cure
There are a growing number of psychologists who believe that one of the main causes of depression (which would also apply to the kind that is spiritual) is negative, demanding and pessimistic thinking. This type of "stinking thinking" helps create an attitude of low self-worth and self-esteem. One 'cure' for this type of problem is postive reinforcing self-talk.