Q - Are some people really demon possessed?

A - Yes, however there's a differences in demon possession and being influenced by evil.

there are many people that are being influenced by evil (we all are to some degree) and then there are those that are demon possessed.

Most people that are demon possessed seem to have two personalities, sometimes they are very nice and likeable when they are themselves, and other times they seem like another person, they may be mean or evil in many ways when the demon is in control of them, they can hurt people and do almost anything, but the normal person would never do these things. Now this would be a bad case demon possession with a high level demon.

People that totally ignoring and rejecting anything to do with God and claims to be spiritual are likely to be demon possessed.

There are also lower level demon possession where they just torment the person by making them believe they are a bad person or they can't trust anyone, they can make a person feel bad about themselves and worthless and yes they can and do deceive those people and this is a lot more common than you might think.

Anyone that is into the new age stuff is at a high risk, because people that go ghost hunting and talk to spirits are at a high risk of demon possession. Hundreds of normal people each year are demon possessed when they use the Ouija board.

TV shows like ghost hunters and most hunted teach people to go to cemeteries and talk to spirits and ask them to interact with them; this puts people at a high risk.