This title discusses nightmares, explaining what is known, suspected, and still mysterious about them, as well as why they might even have a positive effect on lives.We've nearly all been there at least once - awakened with a pounding heart and the memory of frightening scenes that seemed so real, but were conjured up and existed only in the sleeping mind. Nightmares affect people across countries and cultures, with some 10 percent of the world's population reporting recurrent nightmares. Parents have reported, and science has recorded, nightmares in children as young as 18 months old. Up to 40 percent of children aged 2 to 12 experience nightmares, as do some 35 percent of veterans and 50 percent of adults with chronic illness. With this book, the author shows how nightmares evolved and were useful to ancestral populations, and why nightmares may carry beneficial functional effects for people who suffer from the pulse-racing dreams.The author details the up to date findings on the biology of a nightmare and what, specifically, happens in the brain during the event. He also explains the history and development of nightmares and likely causes, including traumatic events, psychological and physical disorders, and commonly consumed medications.Many examples of nightmares are presented and explained. The content of nightmares is given unusually detailed attention and the latest science on nightmares is succinctly reviewed. Tables in every chapter summarise existing findings and conclusions on nightmares, and strategies for dealing with nightmares are described. In this novel view, the author shows why nightmares can be a helpful adaptive system. The special theme of "spirit possession" which frequently occurs in nightmares is discussed and related to similar themes in horror movies and horror fiction.