I believe in visitation dreams (because I have experienced one), but I think it takes an enormous amount of energy to reach out to earthly bound people. They say our dmt levels are higher when we are dreaming. That's the reason, I believe, that certain loved ones can cross over in our dream state to give us messages and let us know that they are okay. I haven't seen any convincing evidence of ghosts, but like seeking peace said: It's either a separate realm or non existence. The idea of ghosts just haunting places seems unpleasant. Who you gonna call when that happens? haha