I had just lain down in bed, and after a few rounds of changing positions I ended up face down. Almost immediately I felt my body go more and more numb. I tried to “pull” myself out of it, but I was already too deep into the paralysis. Then it was almost as if someone sat down on my back, pressing me deeper into the mattress . . . the weight on my back got heavier and heavier, and I was still not able to move. [Then] the thing on my back got off and laid down next to me. . . . I could feel it lying beside me, breathing. I got so scared and thought that this couldn’t be anything other than real . . . because I had been awake all along. It felt like an eternity before I managed to turn my head towards it. Then I laid eyes on an abnormally tall man in a black suit. He was greenishly pale, sick-looking, with a shock-ridden look in the eyes. I tried to scream, but was unable to move my lips or make any sounds at all. He kept staring at me with his eyes almost popping out when all of a sudden he started shouting out random numbers, like FIVE-ELEVEN-EIGHT-ONE-THREE-TWO-FOUR-ONE-NINE-TWENTY, then laughed hysterically. . . . I started feeling able to move again, and as I came back to a normal state the image of the man became more and more blurry until he was gone and I was able to get up.
Another correspondent, J.D., also described the hallucinations associated with sleep paralysis, including the feeling of pressure on her chest:
Sometimes I would see things like huge centipedes or caterpillars crawling all over my ceiling. Once I thought my cat was on the shelf in my room. She seemed to be rolling around and turning into a rat. The worst was when I would hallucinate that a spider was on my chest. I couldn’t move. I would try to scream. I am TERRIFIED of spiders.
On one occasion, she had a hallucination resembling an out-of-body experience:
I hallucinated that my body floated up to the ceiling towards the end of my bed, and then all of a sudden my body quickly dropped through the floor to the first level of the house and then dropped through that floor and into the basement. I could see everything in each room. The floors did not seem to break when I went through them. I just passed through them.
There was little physiological understanding of sleeping, dreaming, or sleep disorders until 1953, when Eugene Aserinsky and Nathaniel Kleitman at the University of Chicago discovered REM sleep—a distinctive stage of sleep with characteristic rapid eye movements, as well as characteristic EEG changes. They also found that if their subjects were woken during REM sleep, they would always report that they had been dreaming. It seemed, then, that dreaming was correlated with REM sleep.62 In REM sleep the body is paralyzed, except for shallow breathing and eye movements. Most people enter the REM stage ninety minutes or so after falling asleep, but people with narcolepsy (or those with sleep deprivation) may fall into REM at the very onset of sleep, plunging suddenly into dreaming and sleep paralysis; they may also wake at the “wrong” time, so that the dreamlike visions and the loss of muscle control characteristic of REM sleep persist into the waking state. Even though the person is wide awake, he may be assaulted by dream- or nightmare-like hallucinations, made even more terrifying by an inability to move or speak.
But one does not have to have narcolepsy to experience sleep paralysis with hallucinations—indeed, J. A. Cheyne and his colleagues at the University of Waterloo have shown that somewhere between a third and half of the general population has had at least occasional episodes of this, and even a single episode may be unforgettable.
Cheyne et al. explored and categorized a huge range of sleep-paralysis-related phenomena, based on reports from three hundred student subjects as well as a large and varied population who responded to an internet questionnaire. They concluded that isolated sleep paralysis (that is, sleep paralysis without narcolepsy), being relatively common, “constitutes a unique natural laboratory for the study of hallucinoid experiences” but stressed that such hallucinations cannot be compared to ordinary hypnagogic or hypnopompic experiences. The hallucinations accompanying isolated sleep paralysis, they wrote, are “substantially more vivid, elaborate, multimodal and terrifying,” and therefore more likely to have a radical impact on anyone who experiences them. These hallucinations may be visceral, auditory, or tactile as well as visual and are accompanied by a feeling of suffocation or pressure on the chest, the sense of a malignant presence, and an overall sense of absolute helplessness and abject terror. These, of course, are the cardinal qualities of the nightmare, in its original sense.
