Beyond your garden variety nightmare, lie a breed of especially horrifying dream related experiences. Why, you could lose sleep just thinking about them! Here's a look at three such states:
Sleep Paralysis: Sometimes called the "Old Hag" this strange occurrence is not particularly rare, and can happen when the brain has been simultaneously aroused into a waking mode yet still not having shut off the atonia (paralysis) and hypnagogic imagery associated with REM. Often menacing, very real seeming entities are sensed being in the same room. A frightening experience, but made less so, if one is aware of the phenomenon.
Night Terrors: These oddly terrifying dreams are often accompanied with screaming or thrashing about. They generally occur during the first hour or two of slumber and are thought to spring from a deeper non-REM state of sleep, that is not usually aligned with dreams, making them somewhat of a mystery to science. More common in children, they often stop having them by the time they hit puberty. In the case of adults undergoing night terrors, they are usually associated with people who have a high level of stress in their lives.
SUNDS: Sudden Unexplained Nocturnal Death Syndrome is an extremely rare condition that has been reported mainly in Southeast Asia. Generally affecting young adult males, their deaths are the result of heart attacks that could be the result of an extreme reaction to the muscle atonia or breathing difficulties that occur during a sleep paralysis episode. Usually the victims are found lying on their backs, with a fixed expression of terror on their face and little evidence of struggle or movement.