Holding on to anger can lead to depression.
Genesis 4:55 but for Cain and for his offering He had no regard So Cain became very angry and his countenance fell.
One source, but not the only source, of depression is an anger that is of the flesh and not of God. Notice the relationship between Cain being very angry and sadness / depression. Cain became very angry and his countenance fell.
Are you holding on to the wrong kind of anger today? It can be a difficult thing to lay aside. Go to God in weakness and ask for His help. Then after prayer be dilligent to put the anger to death. One example may be a person that you need to forgive. The bitterness you store towards them sours you and can depress you. Forgive them. Do it to please the Lord and also for your own mental health. It also models good behavior before your children.
Scripture quotations taken from the "NASB" ( www.lockman.org )