NHS Choices states that sleep paralysis likely occurs when hormones released by the brain that cause one to fall sleep do not wear off upon the individual's awakening. Certain chemical hormones are necessary for a person to be asleep. If a person awakes, but the brain is still releasing these hormones, the person may find himself in a state of paralysis -- mentally awake, but unable to move.Continue Reading
WebMD explains that during rapid eye movement sleep, the part of sleep where people experience dreams, a person's eyes move around wildly, but the rest of the body remains still. If a person becomes conscious before a REM cycle finishes, he may still be unable to move or speak and experience sleep paralysis.
According to WebMD, there are two types of sleep paralysis: hypnagogic sleep paralysis and hypnopompic sleep paralysis. Hypnagogic sleep paralysis occurs while falling asleep, whereas hypnopompic sleep paralysis occurs while awakening. Both types can be frightening for the individual, and hallucinations during sleep paralysis have been reported.
Alien abductions and being visited by shadowy figures have been reported by people who scientists believe are suffering from sleep paralysis, notes WebMD. This is due to the mixed state of consciousness that is occurring, in which a person is conscious and dreaming at the same time.Learn more about Conditions & Diseases