Why do I think psychics are probably demon-possessed? Its because of an episode in the book of Acts, chapter 16:16-19. Luke writes...
16 One day, as we were going to the place of prayer, we met a slave-girl who had a spirit of divination and brought her owners a great deal of money by fortune-telling. 17 While she followed Paul and us, she would cry out, ‘These men are slaves of the Most High God, who proclaim to you a way of salvation.’ 18 She kept doing this for many days. But Paul, very much annoyed, turned and said to the spirit, ‘I order you in the name of Jesus Christ to come out of her.’ And it came out that very hour.Notice a few things here:
19 But when her owners saw that their hope of making money was gone, they seized Paul and Silas and dragged them into the market-place before the authorities.
1) This girl had a spirit - There aren't a lot of different options for what this could be. A spirit is either the Holy Spirit, an angel, or a demon. Context tells us that this isn't the Holy Spirit, and there's no place in the Bible that an holy angel ever takes possession of a human being. This girl is demon-possessed.
2) The spirit allowed her to tell people's fortunes - When we think about fortune tellers, spirit mediums, psychics or whatever, unless they are phony, they are receiving information from somewhere. This girl was receiving it from a demon, and obviously some of what she predicted actually happened if she was able to continually make money doing it.
3) When the spirit left she couldn't perform this ability any more.
4) She appeared to be offering a service that helps people, even though she was granted her ability by the father of lies.
5) The spirit had accurate knowledge of who God is - You might think from this woman's proclamation that she was a prophet of God or servant of God. She was trying to discredit their message by associating herself with it. Often psychics will speak about Jesus as if they know him. They can have right knowledge of God without loving him and submitting to him as Lord.
My advice is this: stay away from psychics, pet psychics, spirit mediums, and anyone who does not point specifically to Jesus Christ. For "even Satan disguises himself as an angel of light" (II Corinthians 11:14). Ask: Does this person aim to glorify Jesus with her/his ministry? Does this person openly and frequently acknowledge Jesus is Lord (See I Cor.12:3)? A psychic or false teacher will appear attractive, wise, and may even speak of Jesus and heaven. Unless they say that Jesus is Savior, God, and Lord, they're most likely either phony or demon-possessed.
PS. Psychics and spirit mediums are most likely not intentionally doing harm, but rather have been taken captive by Satan to do his will. It would be appropriate for a person to repent of his/her admiration for a psychic's abilities and begin praying that the psychic would be saved through faith in Jesus Christ.