When she awoke one morning at 3.a.m., Hannah Foster suffered through a living nightmare more terrifying than a horror novel. She was paralyzed, unable to move even a finger, and felt as if a great weight was suffocating her. Panicked, she tried to scream but could not utter a sound. Foster, a 25-year-old from Brighton, in the U.K., who was interviewed by the Daily Mail, had been hit with a common affliction called sleep paralysis (SP).
The condition affects anywhere from 15 to 40 percent of the population at least once in a lifetime, according to an estimate from sleep disorder specialist, Nidhi Undevia, M.D., medical director of Loyola Center for Sleep Disorders in Chicago.
"In some cases, hallucinations may occur," says Dr. Undevia. "One patient reported seeing elephants, another saw a monster at the foot of his bed. Others may sense that someone else is in the bedroom with them or hear strange noises." People are in a dream-like state when SP hits, half awake, half asleep, says Dr. Undevia. "Often touching the person or talking to them breaks the hallucination and the person wakes up. The episodes may occur at the beginning of the night or in the middle. People become terribly frightened and need reassurance."
Episodes of SP occur during non-REM sleep, the phase of sleep not as deep as the rapid eye movement phase. Oddly, the paralysis or atonia -- the medical term -- in which the victim can't move a muscle, is common, says Dr. Undevia. SP may last a second or two or for several minutes. Some people experience repeated episodes in a single night, several times a week, or many over a lengthy period of time, says Dr. Undevia.
Among the causes of SP are sleep deprivation, interrupted sleep caused bysleep apnea or other factors or narcolepsy, according to Dr. Undevia. There may also be a stress factor, although studies have not been conclusive on that point. In Foster's case, she continued to experience SP every couple of months, including situations in which hallucinations occurred.
"The second time, I knew what was happening -- but as well as the paralysis, I also saw a terrifying black figure … (that) looked a bit like a demon," she told the Daily Mail.
Foster believes that the stress of leaving her position at a university and starting a new job caused her episodes. She has not been cured of her condition, but now has a means to cope. "Each time it happens, I tell myself not to panic, that it's not real," she said. "But even though I know rationally what's going on, it can still be pretty frightening."
But there's hope for all who suffer from SP, according to Dr. Undevia. "Treating the underlying causes usually resolves the problem," she said.