Satan’s powers on flesh
Not all physical or mental illness is caused by demons. The gospels make a clear distinction between illnesses with a demonic base and those without. Nevertheless, some illnesses and distresses do have a demonic foundation. Satan can control a person’s body but the battle is mostly won in the mind (Philippians 4:8; 2 Corinthians 10:5; “sound mind” – 2 Timothy 1:7).
In some cases demons are said to be the cause of physical distress: Deafness and muteness (Matthew 9:32-33; Mark 9:25; Matthew 12:22; Luke 11:14). Blindness (Matthew 12:22). Convulsions/seizures (Mark 9:20). Crippling (Luke 13: 16). Violent action (Luke 8:26-29), Back problems (Luke 13:11). Superhuman strength (Mark 5:4).
In other cases demons are said to be the cause of mental or psychic disorders: Torment (Mark 5:5). Mental disorder (John 10:20), Depression (1 Samuel 16:14-16,23). Physical harm to oneself (Mark 5:5). Suicide (Mark 9:22). Satan and his demons also inspire a spirit of fear (Romans 8:15; 2 Timothy 1:7). This might include a fear of death (Hebrews 2:14-15), fear of man (Proverbs 29:25), worries and anxieties (Philippians 4:6; 1 Peter 5:7), and night terrors (Psalm 91:5).