Although physical depression can be the result of not taking care of your body with fresh fruits,vegetables, dairy products, sunshine and etc but we need to remember that most of the times depression is an spiritual bondage and oppression from demonic forces. There is a spirit of heaviness and depression and is job is to oppress you so you will not be able to function as a person who is called by God to do His will. Depression can disable and suck the life out of you. God has given you authority over the powers of darkness and you can cast this demon out of your life by speaking out loud. Say this:” I reject spirit of depression, I refuse to yield to you devil, I refuse to be sad and depressed, Joy of the Lord is my strength, get out of my life and my house in the Name of Jesus.” and continue to declare who you are in Christ.