Healing includes deliverance from the influence of evil spirits.

First:

What I will be sharing has been gleaned from over twenty years of study and experience. I have found it most helpful.

No one, it seems, fully understands why some are healed and some are not. Still, experience has taught that there are barriers to healing that can be removed if we are willing to deal with them. Following are five very important things that have proven to be hindrances to healing, the baptism in the Holy Spirit and other of God's blessings that, when dealt with, have made the difference. The antithesis to this is to take a prescription.  It does not cost anything.  I has no bad side-affects, and you can't overdose it.  It is to say, "Thank you, Jesus".  You are not thanking Him for your trial, you are thanking Him as an expression of your faith that he will meet your need.

UNBELIEF
"Jesus left there and went to his hometown, accompanied by his disciples. When the Sabbath came, he began to teach in the synagogue, and many who heard him were amazed. "Where did this man get these things?" they asked. "What's this wisdom that has been given him, that he even does miracles! Isn't this the carpenter? Isn't this Mary's son and the brother of James, Joseph, Judas and Simon? Aren't his sisters here with us?" And they took offense at him. Jesus said to them, "Only in his hometown, among his relatives and in his own house is a prophet without honor." He could not do any miracles there, except lay his hands on a few sick people and heal them. (Mark 6:1-5) (NIV)

Here we see that the power of unbelief is greater than even Jesus' power to heal and is therefore a barrier. Even though some saw miracles performed, they still did not believe. (Also see Matthew 15:21-28) Belief is demonstrated when we go to Jesus and ask Him for our needs. And then, believing, we start thanking Him for what we believe by faith we have received or will receive.

HOLDING UNFORGIVENESS
Not forgiving is possibly the greatest barrier to healing, because the next barrier cannot be removed until this one is removed, as we will see.

Forgive us our debts, as we also have forgiven our debtors. And lead us not into temptation, but deliver us from the evil one. For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins." (Matthew 6:12-15) (NIV)

Mark 11:25-26-25 And when ye stand praying, forgive, if ye have ought against any: that your Father also which is in heaven may forgive you your trespasses. 26 But if ye do not forgive, neither will your Father which is in heaven forgive your trespasses. (KJV)

[ Jesus said: "If ye forgive men their trespasses, your heavenly Father will also  forgive you: but if ye forgive not men their trespasses, neither will your Father forgive your trespasses" (Mt. 6:14-15). This is a solemn warning that is commonly overlooked, even by zealous Christians. The real problem with the sin of unforgiveness is that it is an on-going condition of a person's heart. Let's look at some of the reasons for a person having an unforgiving spirit. Unforgiveness can result from self-love. When we love our selves more than others including our enemies, and someone else sins against us, then in essence that self-love says, 'How dare you to sin against me!' God commands us to love our neighbors and even our enemies. Love is greater than faith. Love is greater than hope. And even if you have the gift of prophecy, one of the greatest spiritual gifts, and do not have love you are nothing (1 Cor. 13:2). Love bears all things (1 Cor. 13:7). Unforgiveness is proof of a lack of genuine love in your heart. One sad thing about harboring the sin of unforgiveness in your heart is---you're the loser, now and for all eternity. Concerning now, the apostle Paul wrote that we should forgive, "lest Satan should get an advantage of us" (2 Cor. 2:11). And concerning eternity, it will involve at least the loss of rewards. Peter said, "Lord, how oft shall my brother sin against me, and I forgive Him? till seven times? Jesus saith unto him, I say not unto thee, Until seven times: but, Until seventy times seven" (Mt. 18:21-22). And Paul said, "Be ye kind one to another, tender-hearted, forgiving one another, even as God for Christ's sake hath forgiven you" (Eph. 4:32). "Forbearing one another, and forgiving one another, if any man have a quarrel against any: even as Christ forgave you, so also do ye" (Col. 3:13).]

Again, much can be said about this obstacle to healing, but the crux of the matter is that God commands it -- and will help us do it. But the decision to do so is ours. It is an act of our will in obedience to God. Here is a simple prayer you can say when you are ready to forgive:

Lord, I have a confession to make: There are certain people I have resented and I call upon you now to help me forgive them. 
Lord Jesus, I do now, in obedience to your word, and by an act of my will, forgive the following people for anything they have ever done to hurt or disappoint me: [Now ask the Holy Spirit to bring to our mind  the name of every person, living or dead, that  we may need to forgive.] -- In Jesus' name, Amen.  I also forgive myself. Thank you, Jesus.
Now, Lord,  I ask you to help me change any negative feelings I have held about  others and heal me of anything that has been a consequence of my disobedience to Your Word by holding unforgiveness towards someone.   

We can help them, in turn, to forgive us if we apologize to them for holding any hard feeling and asking them to forgive us.  Whether or not they forgive us is up to them.  It is helpful to ask God to bless them.

UNCONFESSED SIN
Any sin that has not been confessed, repented of, renounced and been forgiven by God also can be a barrier to healing. This especially applies to healing of the mind, emotions, and memories. Since many physical ailments are often psychosomatic, it may be necessary to first heal the cause and then the physical healing will follow. Scripture says that God will not listen to the prayers of those who continue to hold this iniquity in their heart. (Also any disobedience to God or sin that is not dealt with is an open door for an evil spirit.)

If I had cherished sin in my heart, the Lord would not have listened. (Psalm 66:18) (NIV)

If healing has not occurred, we should ask the Holy Spirit to reveal to us what might be the barrier. Then we must be honest with ourselves about anything He reveals to us and act accordingly. Generally, this can be resolved between us and God. Still, there may be times when we have sinned against others. In these cases, we need to make restitution and ask their forgiveness.

RENUNCIATION OF THE OCCULT
Any involvement in the occult is an abomination to God. Even a trivial interest in these areas can have severe and prolonged consequences. It is important to understand that we can renounce occult involvement for ourselves and also our ancestors who may have been in any of these practices. Such involvement can affect descendants to the third and fourth generation.

"The LORD is slow to anger, abounding in love and forgiving sin and rebellion. Yet he does not leave the guilty unpunished; he punishes the children for the sin of the fathers to the third and fourth generation." (Num 14:18) (NIV)

"There shall not be found among you anyone who makes his son or his daughter pass through the fire, one who uses divination, one who practices witchcraft, or one who interprets omens, or a sorcerer, or one who casts a spell, or a medium, or a spiritist, or one who calls up the dead. For whoever does these things is detestable to the LORD; and because of these detestable things the LORD your God will drive them out before you." (Deut 18:10-12) (NIV)

For  a complete list of things that may need to be dealt with go to this page

Although there is much to be said about this subject, making the following confession has proven to be effective:

Hear is a declaration by Derek Prince

A declaration to Satan based on Psalm 118:17
I shall not die but live and declare the works of the Lord.
My body is the temple of the Holy Spirit, redeemed, cleansed and sanctified by the blood of Jesus. My members and the parts of my body are instruments of righteousness for His service and for His glory. The devil has no place in me, no power over me, no unsettled claims against me. It has all been settled by the blood of Jesus. I overcome Satan by the blood of Jesus and by the word of my testimony and I love not my life unto the death. Amen!

"Dear Lord, I have a confession to make. Through ignorance, or willfulness, I have sought supernatural experiences apart from You. I have disobeyed your Word and I ask you to deliver me, as I renounce all these things. Cleanse me in body, mind, soul, and spirit, I pray. 
 I for myself and my ancestors renounce, forsake and turn away from  all contact with witchcraft, magic, ouija boards and other occult games;
· I renounce for myself and my ancestors  all kinds of fortune telling, palm reading, tea leaves reading, crystal balls, tarot and other card laying.
· I renounce for myself and my ancestors all astrology, birth signs and horoscopes.
·I renounce for myself and my ancestors the heresy of reincarnation and all healing groups involved in metaphysics and spiritualism.
· I renounce for myself and my ancestors all hypnosis under any excuse or authority.
· I renounce for myself and my ancestors all music that in any way is contrary to the Word of God.
·  I renounce for myself and my ancestors all transcendental meditation, and all other eastern cults and idol worship.
· I renounce for myself and my ancestors all martial arts, including judo, kung fu, and karate that in any way convey supernatural power that is not from God.
· I renounce for myself and my ancestors all water witching [or dowsing], levitation, table-tipping, psychometry [divination through objects], automatic writing, and handwriting analysis.
· I renounce for myself and my ancestors all literature I have ever read and studies in any of these fields. I promise I will destroy all such material in my possession.
· I renounce for myself and my ancestors astral projection, soul and out-of-body travel and other demonic skills.
· I renounce, for myself and my ancestors  in the Name of the Lord Jesus Christ, all psychic power that I may have inherited and break any demonic hold or curse on my family line back to ten or more generations on both sides of the family.
· I renounce for myself and my ancestors and forsake every psychic and occult contact that I am unaware of, as well as those I may have forgotten.
· I renounce for myself and my ancestors every cult that denies atonement through the blood of Jesus Christ and every philosophy that denies His deity.
I promise to destroy any occult paraphernalia that I posses since they are an abomination.  (See footnote)
· Now, Satan, I cast down any strongholds that these activities may have established, and close any door I may have opened to you through these contacts.

DEMONIC INFLUENCE
Since physical affliction can be caused by an evil spirit -- whether we are aware of any presence or not -- so this possibility should not be overlooked. If deliverance - the expelling of an evil spirit --  is needed, nothing else will suffice. If this is not the cause, there are no adverse consequences from acting on the possibility anyway.

"How God anointed Jesus of Nazareth with the Holy Spirit and with power, who went about doing good and healing all who were oppressed by the devil, for God was with Him." (Acts 10:38) (NIV)

Proclaim with the authority what we have in the name of Jesus Christ of Nazareth the statements below marked in bold below. In stubborn cases it may be effective to repeat it more than once until the release is felt. Including the appropriate scriptures may make a difference. It has been proven to be an effective weapon against the attacks that can come upon Christians at any time. This is not a prayer. It is a proclamation! We are speaking directly to Satan's kingdom of darkness, so we speak with authority. Here is a more exhaustive list of thing that may, in some cases, need to be renounced. Occult Check list

A recommended declaration for breaking a curse by Derek Prince based on Psalm 118.17 found on his cassette tape "Overcoming the Barriers to Healing" tape number B-4150

I shall not die but live and declare the works of the Lord  My body is the temple of the Holy Spirit, redeemed, cleansed, and sanctified by the blood of Jesus.  My members and the parts of my body are instruments of righteousness yielded to God for His service and for His glory. The devil has no place in me, no power over me, no unsettled claims against me.  All has been settled by the blood of Jesus.  I overcome Satan by the blood of the lamb and the word of my testimony and I love not my life unto the death. My body is for the Lord, and the Lord is for my body.  Amen

                               Can a Christian have a demon?

The COVENANT OF THE BLOOD

Declare with emphasis the words highlighted in bold. Remember we are not praying, but we are declaring to Satan what the blood of Jesus does for us. Also, quoting the Scripture can be effective. This is recommend as a way to expel an evil spirit.

· Satan: I testify to you personally what the Word says the SHED BLOOD does for me!

[Revelation 12:11a] They overcame him [Satan] by the Blood of the Lamb [Jesus Christ] and the word of their testimony.

 [That is, the believers on earth testified to what the Word of God says about the Blood of Jesus.]

Through the SHED BLOOD OF JESUS, I am redeemed out of the hands of Satan! [Psalm 107:2]

Let the redeemed of the Lord say so, whom He has redeemed from the hand of the enemy. In whom we have redemption through His Blood, the forgiveness of sins, according to the richness of His grace. [Ephesians 1:7]

Through the SHED BLOOD OF JESUS, all my sins are forgiven!

Giving thanks to the Father, which has made us meet to be partakers of the inheritance of the saints in light: Who has delivered us from the power of darkness, and has translated us into the kingdom of his dear Son: In whom we have redemption through his blood, even the forgiveness of sins. [Col. 1:12-14]

 The through the SHED BLOOD OF JESUS, all my sins are forgiven!

The SHED BLOOD OF JESUS is cleansing me now from all sin!

But if we walk in the light, as He is in the light, we have fellowship one with another, and the blood of Jesus Christ, His Son, cleanses us from all sin. [1 John 1:7]

 I am justified, made righteous, just-as-if-I'd never sinned, through the SHED BLOOD OF JESUS!

Much more then, now justified by His blood, we shall be saved from wrath through Him. [Romans 5:9]

Through the SHED BLOOD OF JESUS, I am sanctified, set apart to God!

Wherefore Jesus also, that He might sanctify the people with his own blood, suffered without the gate. [Hebrews 13:12]

My body is a temple of the Holy Spirit, redeemed, cleansed, sanctified, through the SHED BLOOD OF JESUS!

 What? Know you not that your body is the temple of the holy Spirit, which is in you, which you have of God, and you are not your own? For you are bought with a price: therefore glorify God in your body, and in your spirit, which are God's. [1 Corinthians 6:19-20 ]

I belong to Jesus Christ, God's Son, spirit, soul, and body! His SHED BLOOD protects me from all evil!

 Behold, I give to you power to tread on serpents and scorpions, and over all the power of the enemy: and nothing shall by any means hurt you. [Luke 10:19]

· Because of the SHED BLOOD OF JESUS, Satan, you have no more power over me and therefore no place in me! I renounce you and your hosts completely, and declare you to be my enemies!

 Mark 16:17, Jesus said, "These signs shall follow the believer. In my name they shall cast out devils."

I am a believer! In the name of Jesus of Nazareth, I exercise my God-given authority to expel all evil spirits. I command them to leave me now, according to the Word of God, and in the name of Jesus!
 Specifically name any spirit that you have reason to believe might need to be expelled. Ask the Holy Spirit for guidance and respond to what He tells you. And finally,

I forbid any enemy spirits to return and I close any doors I may have opened to them. Amen!

Curses also may need to be dealt with.  See:http://www.bible.com/answers/acurses.html

There is a resource I would highly recommend if there is one near you called "Healing Rooms if there is one near you.  You can find out at:  http://healingrooms.com