This week’s installment of scary sleep disorders will probably give you nightmares. Consider yourself warned…
It has never happened to me. At least not that I know of. But I imagine it would be something like that feeling you get when the alarm clock rings during a too-deep afternoon nap and suddenly you can’t recall where you are, how you got there, and whether it’s night or day. Except it would be much worse, multiplied by a number with at least 6 digits, and instead of quickly orienting to your surroundings, the panic would persist, even escalate until somehow you relapsed back into sleep, neither understanding nor remembering the cause of your distress. And there would be a name for the experience. It would be called a night terror.
In part one of this series I mentioned that there are three states of consciousness – waking, REM sleep* and non-REM sleep – and that mixing them yielded strange phenomena. Night terrors are among these. They are a mixture of waking and slow-wave sleep (SWS), one of the subcategories of non-REM sleep.† They typically occur during an abrupt transition from SWS to wakefulness. SWS generally occurs during the first few hours of sleep and thus so do night terrors, after that more time is given over to dreaming.‡
As with many parasomnias §, night terrors are more common in children than in adults, however the problem can persist into adulthood. Figures on the prevalence of night terrors are too varied for me to bother disseminating any of them here, but I will mention that adults prone to night terrors have been reported to be higher than average in personality traits of anxiety and hysteria. It is a dramatic event. The night terror often begins with a loud “blood-curdling” scream. The sleeper is panicked and confused, their heart racing. They may thrash about, or even jump out of bed and run around**. Often, they return to sleep without fully awakening. In the morning they will have no memory of the sleep disturbance that freaked out their roommates or bedmates.
A characteristic symptom of a night terror is complete inconsolability. No amount of, “There, there, darling, you just had a nightmare…” will do any good. And, in fact, the sleeper did not have a nightmare.†† As they occur in non-REM sleep, night terrors are strikingly content-free. There is no cause of the panic, just panic.
Sleep paralysis is a rather different amalgamation of conscious states than a night terror. I had initially conflated the two disorders, having heard a description of sleep paralysis somewhere and the term “night terror” somewhere else. The name seemed a good match for the phenomenon, which sounded unequivocally terror-inducing. While a night terror is a mixture of wakefulness and slow-wave sleep, sleep paralysis is the troublesome commingling of wakefulness and REM sleep. As the dreaming sleeper begins to emerge from REM sleep, they open their eyes and take in their surroundings. Unfortunately the rest of their muscles are still paralyzed from being in the REM state. They feel pinned down and, naturally, frightened. There may be a sense of a menacing presence in the room. Sometimes the dreams of REM sleep also linger in the form of auditory and visual hallucinations.
Unlike the sufferer of night terrors, a person experiencing sleep paralysis will still remember their chilling ordeal after the sun rises. Prior to the scientific study of sleep (and the advent of polysonography) all manner of ghost stories emerged to explain the incident. Something sinister and supernatural was holding the victim down, suffocating them. Incubi, succubi, vampires, hags and various ghoulies and ghosties and things that go bump in the night where clearly responsible. Witches were casting spells, they called the sleeper’s name (auditory hallucination) as they used their magic to bind their helpless prey to his or her bed. In more modern cultures, it has been suggested that the belief in alien abductions is the latest form of the waking brain trying in vain to make sense of what the hell is happening to the sleeping body.
There’s something of a positive feedback loop happening in the interpretation of the sleep paralysis experience. The sleeper makes their first grasp at an explanation while the event is still occurring. These ideas can give more vivid form to the hallucination, increasing the sense of fear.
Not everyone perceives sleep paralysis as a sensation of being held down or chocked. Some interpret the immobility of their muscles as an out of body experience. They are floating. They are flying. This is not necessarily reported as an unpleasant experience, but one can easily see how it might also fit the stereotypical description of an alleged alien abduction. There are even those who don’t impose any mythology onto their encounters with sleep paralysis. They just chalk it up to random weirdness and hope it doesn’t happen again.
Prevalence of sleep paralysis follows a similar pattern to that of night terrors – more common in childhood, difficult to assess the exact proportion of the adult population afflicted with the parasomnia. I encourage you to do your own demographic research during your Halloween escapades. A good-sized party should provide at least a few colorful anecdotes amongst the guests. Over the past week, I read so much about night terrors and sleep paralysis that I began to wonder if one could inadvertently summon the conditions by thinking about them excessively. You should consider this too, while you drift off to sleep tonight. Sweet dreams.
* Not that I doubt your faithful weekly readership, but just in case you missed part one, I’ll restate that REM sleep is where dreaming generally occurs. During this stage the voluntary muscles of the body are also paralyzed.
† The stages of sleep are 1-4 and REM and are categorized by brainwave activity, eye movement, etc as captured by polysomnography. Slow wave sleep is stages 3/4. The order of the stages is not simply sequential as can be seen in the typical sleep hypnogram shown here.
‡ Intriguingly, people prone to night terrors sometime exhibit periods of SWS later into the night as well. It has been suggested that the disruptions to earlier periods of SWS causes it to reappear throughout the sleep cycle.
§ Parasomnias are unwanted behavioral or experiential phenomena that occur during sleep, as opposed to problems with the physical processes behind sleep (such as insomnia or narcolepsy).
** Night terrors are a close cousin of sleepwalking, another parasomnia brought on by the combination of waking and non-REM sleep.
†† Just to further complicate the issue, I’d like to point out that the word “mare” and variations of it exist in several languages with meanings usually corresponding to some form of supernatural creature. It is likely that the term “nightmare” was originally used to describe sleep paralysis rather than its current usage to denote bad dreams.
Who told you this?
Mahowald, M.W. and Schenck, C.H. 2005. “Insight From Studying Human Sleep Disorders.” Nature 437: 1279-1285.
Laberge, L. et al. 2000. “Development of Parasomnias From Childhood to Early Adolescence.” Pediatrics 106: 67-74.
Szelenberger, W. et al. 2005. “Sleepwalking and night terrors: Psychopathological and psychophysiological correlates.” International Review of Psychiatry 17: 263-270.
Crisp, A.H. 1996. “The sleepwalking/night terrors syndrome in adults.” Postgrad Medical Journal 72: 599-604.
McNally, R.J. and Clancy, S.A. 2005. “Sleep Paralysis, Sexual Abuse, and Space Alien Abduction.” Transcultural Psychiatry 42: 113-122.
Cheyne, J.A. et al. 1999. “Hypnagogic and Hypnopompic Hallucinations during Sleep Paralysis: Neurological and Cultural Construction of the Night-Mare.” Consciousness and Cognition 8: 319-337.