1 Peter 5:7-8 “Cast all your anxiety upon the Lord, because He cares for you. Be alert with a sober mind. Your enemy, the Devil, prowls around like a roaring lion for someone to devour.”
There is strong Biblical evidence that a Christian cannot be demon-possessed. But the question remains about how much influence demons have over a Christian. Most theologians describe demonic influence on Christians as “demonic oppression” to distinguish it from possession. Oppression causes spiritual and physical trouble.