Drawn from the account of the demoniac of Gadara in Mark 5, the first six symptoms are extreme. The man in that passage was controlled by a legion of demons and had been chained in a cemetery because of his erratic and violent behavior. Other signs of demonic activity may be subtler, but they are no less dangerous and shouldn’t be ignored.
1. Incapacity for normal living (see Mark 5:1-5). The actions of legion made him unsuitable for normal social interaction with friends and family. An unusual desire for solitude, accompanied by a deep loneliness, will often set in. The person will often become very passive with no desire to change.
2. Extreme behavior (see Mark 5:4). An explosive temper and extreme uncontrollable anger could be signs of demonic activity. These are dangerous behaviors that control the individual and affect surrounding loved ones.
3. Personality changes (see Mark 5:9,12). Changes in personality, extreme or mild, may be evidence of demonic activity. And though all cases of multiple personality may not be demonic, in most cases demon activity is involved.
4. Restlessness and insomnia (see Mark 5:5). The demoniac cried in the tombs “night and day.” He couldn’t sleep. Insomnia can be a sign of a physical or spiritual problem. God has gifted His children with sleep (see Ps. 127:2). So when you can’t sleep night after night and there is no medical reason, the devil may be tormenting you.
5. A terrible inner anguish (see Mark 5:5). Grief and anguish are normal emotions. Yet persistent unresolved anguish that won’t leave after normal therapies of counseling, encouragement and prayer could well be demonic.
6. Self-inflicted injury and suicide. In Mark 5:5, the demonized man was cutting himself. And in Mark 9:14-29, a man’s son was both deaf and mute because of a demon, and the evil spirit would often throw the boy into fire and water to destroy him. Demons can cause people to injure themselves and even incite suicide.
7. Unexplained illness. When medical testing produces no physical cause for an illness, then we should look to the mind and spirit for answers. Sometimes illnesses are psychological, and good counseling can result in a cure. Other times the battle is with demons. Luke 13:11-16 tells the story of a “daughter of Abraham” who was afflicted by a “spirit of infirmity.” Although she was a child of God, she was tormented by illnesses caused by this class of demons.
8. Addictive behavior. Addiction to alcohol, drugs, sex, food, gambling and other things opens the door to demonic influence and control. I’m not saying demons cause all of these problems. But anything that causes one to be out of control opens that person to infernal control.
9. Abnormal sexual behavior. The spirit of harlotry is mentioned several times in Ezekiel 16:20-51. This spirit infected the nation of Israel with the sins of Sodom and even motivated the people to sacrifice their own children. Homosexuality, adultery, fornication and even infanticide were all inspired by the spirit of harlotry (see Hos. 4:12). And nations and families are sold into spiritual bondage by the witchcraft of this spirit (see Nah. 3:4). When we play around with sexual sin, we open ourselves to this demonic spirit. We must battle this principality that dominates our nation.
10. Defeat, failure and depression in the Christian life. It is Satan’s purpose to rob us of the victorious life that is ours in Christ (see 2 Cor. 2:10-14). This symptom is often manifested by an inability to praise and worship, which is a weapon of warfare. In Psalm 106:47, David asks God for salvation so he could “triumph in [God’s] praise.”
11. Occult involvement and behavior. Occult involvement is clearly a symptom of demonic control. Deuteronomy 18:9-12 catalogs the works of the occult, including child sacrifice, fortune-telling, sorcery and calling up the dead.
12. Speech difficulties. In Matthew 9:32-33, Jesus rebuked a demon, and the mute man was able to speak. Speech difficulties may be physical, emotional or mental, but in some cases they are demonic. Extreme language and cursing also may be prompted by the enemy.
13. Doctrinal error. First Timothy 4:1 warns that in the last days deceiving spirits will teach the doctrines of demons. Today religious cults and charlatans abound. The reason these deceivers draw many people is the power of the demonic that teaches them.
14. Religious legalism. In Galatians 3, the church at Galatia had forsaken a faith ministry that resulted in the miraculous for a law ministry of rules and regulations. Paul classified this error as witchcraft. Some deeply religious people are under the bondage of tradition, man-made rules and outward appearances. Demons thrive in this kind of environment, especially demons of control. Whenever something is substituted for faith in the finished work of Christ, it is a doctrine of demons.
Bill Wiese 
Paul McGuire 
