A ghost is a consciousness whose body has dropped but not the mind. And the mind demands a body, because all desires and passions of the mind can be fulfilled only through a body. Its mind wants to touch some lovely body. If you are weak and without any will, some ghost can push his way inside you, because it does not have a body and its desires are burning.
Robert Allen Monroe,popularly known as Bob Monroe, is a author of famous 1971 book " Journeys Out of the Body " and is credited with popularizing the term "out-of-body experience" . Bob Monroe was a New York radio broadcasting executive who later became famous for his research into altered consciousness. Following is a informative vintage interview with Bob Monroe circa 1979.