I do not believe they are for the following reasons:
1. The Bible nowhere calls it a sin
2. Many of the great characters of the Bible experienced both
discouragement and depression
3. Neither David, Paul, Jeremiah nor others were rebuked for being
discouraged
4. Discouragement and depression could be the weakness in which
God is made strong in us
5. Charles Spurgeon, himself a well known sufferer if depression,
once said, "Discouragement is the lot of the preacher. God will not share
his glory."[1]
Though discouragement might lead a person to behave in a sinful
way it is not necessarily so and it is not the discouragement that is the
actual cause of the sin. As with any testing, a person has the ability to use
that test to draw them closer to God or push them further away from God.
Depression may be the tool used if the Lord to greatly use a man.[2]
Marvin McKenzie
In the field