I would define oppression as being what Paul was contending with when the woman with the demon was following him around, the demon in the woman had to be rebuked. This demon was a burden and distraction to Paul's ministry.
So I believe that a person can be oppressed in this way by a demonic presence that needs to be rebuked. That does Not mean that that presence is IN them. As it would be in the case of possession.
This has been a big question for years. Is there a defining moment when a person is completely controlled or just under the influence.
In meekness
instructing those that oppose themselves; if God peradventure will give them repentance to the acknowledging of the truth; And
that they may recover themselves out of the snare of the devil, who are taken captive by him at his will.
(2Ti 2:25-26)
The women that followed Paul around for 3 days was not crazy, as she knew who Paul was and made a conscience choice to follow Paul. One thing to take note, is that Paul waited 3 days before dealing with the spirit that was attached to her. I fully believe Paul had to hear from the Holy Spirit first, as that women was hearing truth also. We deal with a devil in a persons life when instructed. Otherwise we give truth so that they may use that to recover themselves, submit to God, and the devil has to run.
Talking with someone in deliverance ministry who was a guest at my house, told me that sometimes it takes the power of the anointing and command to get devils to leave a person so that they may think clearly. This would be the part to rebuke and tell the devil to leave in the name of Jesus. In other words, He said just giving person the truth is not enough as that truth is subverted into something else through the evil spirit and into the persons mind.
The Lord gave me this definition of what possessed is. It can effect believers, and non believers.
Any person that is unable to "SEE" truth through their own hearing, because of unclean spirits enforced stronghold in their life. A person that will need my grace and power to remove that stronghold, that truth can be seen.
While I agree with you about some habits, say someone who is an habitual eater, they are in bondage to that habit which may very well have started as a comfort crutch.
But I would not say that person is serving satan. Nor, would I say that it is demonic.
Anything that is not in perfect harmony with the will of God, is devil influenced through the pull on a persons own lust. Jesus came to destroy the work of the devil, which is the reason he came.
We get a thought that sickness, or just some eating disorder could be just the person and circumstances, and not devils. The spirit realm controls the natural realm. We see something simple like Peter wanting to fight for Jesus a idea of the enemy, and Jesus caught that. Fighting for Jesus seemed like a good thing though, but the devil's Kingdom opposes God's. Anything introduced into a persons life that will destroy their witness, or hinder them from serving God fully, has devils influencing that situation.
Satan has to seek who he devours, that means he just can't come in a run things. He has to find area's of a persons life they will give in. We use to say the devil is always looking for our buttons we have exposed.
Every human being on the planet has a right to tell the devil no. Devils are just disobedient angels and man is not subject to them. This is why it's serious to make yourself subject to a created slave who disobeyed God, and not subject to God.