Horror movies, by their nature, are designed to inspire terror and disgust in the viewer. Although this experience can be tolerated and even desired by adults, a child's mind is not as strong and not as able to separate fiction and reality. In fact, a child's mind (still not fully developed) can be seriously and adversely affected by the viewing of graphic or mentally disturbing horror movies; these disturbances can lead, in some cases, even to outbreaks of violence.
Horror movies often delve into the most guttural psychological fears that humans experience. Fears such as the fear of being devoured (e.g., "Jaws" or "The Texas Chainsaw Massacre"), the fear of being hunted (e.g., "The Island of Doctor Moreau" or "Halloween"). or the fear of losing control (e.g., "The Shining" or "The Exorcist") are all rooted deep in our psychology and our human experience. Whereas most adults have the capacity to separate fears generated from movies and television from fears incurred by actual trauma, a child's mind is not fully developed or fully equipped with an adult's defence mechanisms and sense of perspective. Some children and even some adults can suffer residual anxiety from watching horror movies. Examples of this include a fear of water or swimming after watching a horror movie about sharks or increased religious fervour after being terrified by a movie about the Devil (e.g., "Rosemary's Baby").
Children are often kept up when watching potentially frightening movies, but in some extreme cases sleeplessness can last for weeks or even reoccur months after watching a movie. This situation can be compounded by residual anxiety and can even generate lifelong phobias such as fear of sleeping in the dark, fear of sleeping in quiet, or even a fear of sleeping with others.
One immediate possible impact of watching horror movies for some children is fainting. This happens when the mind does not distinguish between trauma watched for entertainment and trauma actually experienced. Some children experience everything the victim in a movie is going through as if they were going through it themselves. This can lead to screaming, crying, chills, shortness of breath, and even fainting. A child who experiences physical symptoms such as these should be taken out of viewing range or earshot of a movie immediately and helped to think about other things.