The fear of ghosts in many human cultures is based on beliefs that some ghosts may be malevolent towards people and dangerous (within the range of all possible attitudes, including mischievous, benign, indifferent, etc.). It is related to fear of the dark. A persistent fear of ghosts is sometimes called phasmophobia, a type of specific phobia. It derives from the greek words "phasma" meaning "apparition" and "phobos" meaning "fear". It is often brought about by experiences in early childhood and causes sufferers to experience panic attacks.