Is demonic possession possible?

If demons exist, there is no reason to think they could not possess someone.

If you are a Christian, then you can read how Jesus expelled demons with a simple command (Mark 1:23-26; 9:14-29; Luke 11:14-26), and how the apostles continued the practice with the power and in the name of Jesus (Matthew 10:1; Acts 19:11-16). Also in Romans 6:18. it states: "just as a believer, whom Jesus Christ has delivered from sin, can still be bound by sin in his life, so he can still be bound by a demon in his life."