Demon Possessed

If we are to understand what demonized means we must surly look at New Testament descriptions of demonized men and women. As we examine them, I think you will agree that most would better be described as men and women afflicted by demons rather than owned and totally controlled by them. Afflicted in and through their bodies to be sure. Hence the need for the demons to be driven out. But the demons do not own the bodies of Christians.
In many cases there is no clear description, but in several instances there is. The Gadarene demoniac alone might come under the category of someone owned and totally controlled by demons. And yet even in his case the description is not necessarily true. Self-control and demon-controlled seem t alternate in the man. Under his own control he runs to Jesus and falls at his feet. The act looks like an act of worship. But the demon within him then cried, "What do you want with me, Jesus, Son of the Most High God?" (MK 5:6-7).
But take the case of the epileptic boy at the foot of the Mount of Transfiguration. He was afflicted with periodic fits of epilepsy. When Jesus cast the demon out the boy was healed (Mt. 17:18). You can be healed of an affliction, not of a possession. The account of the same incident in Mark is yet more graphic. Here the spirit is described as one of deaf mutism - certainly an affliction from which any of us would wish to be healed (MK 9:14-27).
Again, the Canaanite woman who came to Jesus on behalf of her demonized daughter said that her daughter was "suffering terribly" from her demonization (Mt 15:22). The expression suggests affliction, pain, torment. Moreover when Jesus grants her request we are told that her daughter, like the epileptic boy, was healed. The word healed is used of a bodily affliction, and is comparable more with a sickness a demon causes than with an ownership to which the spirit has no right, even in the unconverted.
Conrad was, I believe, afflicted by a demon. The demonic affliction took the form of an addiction to drugs. It may well have attached itself to Conrad's body at some point during his abuse of drugs, and in this sense Conrad deserved what he got. Unfortunately, though deliverance from many sins follows confession and faith, the matter is less simple when a demonic presence is involved. The abuse had provided an opportunity for demonic attachment of some kind. Not until Ken Blue, under the authority of the kingdom of God and in the power of the Spirit, served notice to the demon was the matter resolved.

John White, When The Spirit Comes With Power, p. 210-211