Frozen About a third of people with severe sleep paralysis say they hallucinate while they're frozen, sometimes picturing a shadowy figure looming over them. It's a state of being awake but completely frozen, unable to move or speak. It usually strikes just after waking up, but can also occur just before falling asleep. Other sufferers have nightmarish hallucinations. They see dark, hooded figures looming over them as they lie helpless in bed.
Some women report feelings of being raped.
Others see bright lights and swear they were abducted by aliens. Neurology offers them a better idea of how common it is and what the risk factors might be. According to a new study, roughly 6 percent of all people have had at least one episode of sleep paralysis, while slightly less than 1 percent have at least one episode a week. Sleep expert Dr. Maurice Ohayon and colleagues came up with those figures by asking 8,100 people in Germany and Italy about their sleep habits. Ohayon, a researcher the University of Montreal, says he would expect the prevalence rate to be about the same in other countries, too.