Often it is misattributed to abuse or chemical imbalances.   

The truth is that abuse provides an opportunity for demons to come into a person's life.   

Chemical imbalances are a result of demonic influence in a person's life.   

Once a demon has established residence in a person's life, there will be signs of Mental Illness in one way or another to a lesser or greater extent.   

Ignorance of or denial of demonic origins of mental and physical abnormalities prevents the healing of these diseases.   Psychologists try to manage Mental Illness while MD's try to manage physical ailments.   

Jesus told us that we must be Born Again to become New Spirit beings enabling us to have power over demonic influences.   

Jesus answered and said unto him, Truly, truly, I say unto you, Except a man be born again, he cannot see the kingdom of heaven. Joh 3:3 Human beings are born with the Sin Nature - a corrupt spirit.     That corrupt spirit is dead to the Lord Gen 2:17.      By being Born Again of the Holy Spirit we can begin to see (understand and appreciate) the Kingdom Of God.      We are born of water - flesh - through our mothers.     We can only be born of Spirit by the Holy Spirit as a result of our reaction to hearing the Word Of The Lord - the Gospel.      By being born of the Holy Spirit through faith in the Word we become New Spirit beings - Sons Of The Holy Spirit.      By being filled with the Holy Spirit and immersed in the Word Of The Lord we enter the Kingdom Of Heaven in the sense that we think from a heavenly perspective and act out of heavenly inspiration.

Being born again, not of corruptible seed, but of incorruptible, by the word of the Lord, living and abiding for ever. 1Pe 1:23 The seed that births us into the Kingdom Of God is the Word Of The Lord - writtern and incarnate.     Both the Incarnate Word and the Written Word abide forever.      By hearing, believing and receiving the Word Of The Lord we are Born Again into the Spirit Realm by our Holy Spirit Father.      Our Lord Jesus Christ is the eternally alive Mighty God and Saviour in Spirit Soul And Body and in Him we too live and abide forever.

The Lord Jesus Christ came to enable us to have Abundant Life which requires us to be Free Indeed.   That freedom involves deliverance from and power over demonic influences.   

And when he had called unto him his twelve disciples, he gave them power against unclean spirits, to cast them out, and to heal all manner of sickness and all manner of disease. Mat 10:1 Jesus gives us the power of His Holy Spirit for us to heal and deliver by His authority.

And they were all amazed, and spoke among themselves, saying, What a word is this!     for with authority and power he commands the unclean spirits, and they come out. Luk 4:36 The authority comes from the Word.     The power comes from the Holy Spirit.     When the Word and the Holy Spirit are exercised, no power can stand against us.

Not understanding that the Saviour came to deliver us from the source of all our problems is a major failure of Christianity.   Satan was able to dumb us down to seeing Christ's work as just saving us from hell after we die.   

Even today many Christians condemn the Prosperity Gospel as if Abundant Life is possible in poverty.   

Most people who have wealth but not health would give up their wealth for health.   

Beloved, I wish above all things that you may prosper and be in health, even as your soul prospers. 3Jn 1:2 Is this just John`s wish or is it the Father`s also?      If just John`s then is he wishing something against the will of the Lord?      No, this is from the heart of the Holy Spirit who loves us and has given us the keys of the kingdom and made us joint heirs with Jesus Christ.

Jesus made people whole which means that He address all of their needs.   
Abundant Life is being prosperous in Spirit Soul And Body.   Our mind is a part of our soul.   

For the Lord has not given us the spirit of fear; but of power, and of love, and of a sound mind. 2Ti 1:7 Fear is a spirit.     It comes from the enemy who steals our peace whenever opportunity arises.      Power is a Spirit.     It is the Holy Spirit.      Love is a Spirit.     It is the Holy Spirit.      A Sound Mind is a Spirit.     It is the Holy Spirit.      Power, love and a Sound Mind are given to us by the Holy Spirit in us.      Never submit to fear, but always submit to the Holy Spirit.     Jam 4:7

Way too many people are raised ignorant of God, are taught to despise Christ and Christians and so attempt to live their lives under the auspices of Satan and his children.   

It is amazing that anyone approximates normality when raised in such conditions.   

Jesus said, "NO!   Except you repent you will all likewise perish."