what does the bible say?
The Bible provides no criteria for determining whether a psychological disorder is linked to a demonic attack. And there is some connection between the two. However, the Bible does show that Satan is limited in what he can do, especially concerning Christians. The Bible teaches that Satan influences and attacks even believers. Job, David, and Peter are examples of this (Job 1:9-12, 2:4-6; 1 Chronicles 21:1; Matthew 16:23). However, believers are indwelt by the Holy Spirit, so they cannot be demon-possessed (1 Corinthians 6:19-20). Unbelievers, though, have no protection (Matthew 12:43-45; Luke 11:24-26). Scripture shows how Satan attacks people by giving them physical ailments, such as muteness, blindness, and other crippling physical deformities (Matthew 9:32-33, 12:22, Mark 9:20-29; Luke 13:11-16). Satan can also influence behavior. Chapter five of Mark recounts the unusual behavior (yelling and cutting himself) of a man in Gerasene who was possessed by demons (Mark 5:5), which shows that demons can cause abnormal behavior. God has not left believers vulnerable to satanic attacks but gives us all we need to defeat Satan (Ephesians 6:10-19; James 4:7).