Suffocation is a unique, distinctly non-intellectual pathway to fear. Just the merest hint of it causes an automatic, guaranteed physiological reaction: CO2 levels in the blood rise and pH levels in the brain's memory and emotional center, the amygdala, drop and there it is. Terror.
That's a good thing, really. A change in the air doesn't otherwise have the same stimulus effect as, say, the point of a knife on your skin or scalding heat. That is to say there isn't pain in the conventional sense; as CO2 goes up past critical levels, in the absence of fear or panic, the body will try breathing harder or faster and, eventually, you'll pass out. And if the whole situation doesn't improve while you're lying there on the floor, death.
So, terror is like pain for suffocation, like being psychically stabbed or burned, albeit with some help from body chemistry. Your body is capable of simulating suffocation in one highly bizarre and accidental circumstance known usually as sleep paralysis. It's a sensation-slash-circumstance potent enough to generate enough folklore throughout human history to fill volumes, most of it gravitating towards the victim being tortured by witches or demons. In a human history full of flayings, scaphism, and other wildly creative ways to induce misery in others, sleep paralysis remains even beyond our reach: the realm of demons.
Sleep paralysis itself feels like just-death or the crux of the dying process.
For whatever reason, the witch or demon left me alone for about 10 years. Between 2000 and 2003, they were after me every night, sometimes several times before morning, and I thought for sure that eventually I'd wake up once just in time to die for real. The distance between what sleep paralysis felt like most times and actual death felt to be about three or four heartbeats and one terrifyingly labored breath. Although that's not totally accurate.
The distance often didn't feel like anything at all. Sleep paralysis itself feels like just-death or the crux of the dying process, or what you might imagine it to feel like when you're being afraid of dying. I never actually died for very long via sleep paralysis, but I did spend many, many hours lying in dark rooms in a state of just-dead. And the other morning, bathed in a particularly sickly dawn orange light, I woke up just-dead again. The feeling lasted for an eternity, and then passed.
"Being ridden by the witch" is the southern Americana folklore term for sleep paralysis. There are many more folk legends worldwide. In Fiji, it's kana tevoro, or being eaten by a demon. It's sometimes cultivated there with shouts of kania! kania! ("eat! eat!") from persons watching the victim in an effort to prolong the experience and enable communication with the dead. In Turkey, it's the djinn (another demon) strangling you in your sleep and is only remedied by reading passages from the Qur'an. In parts of China, it's a mouse stealing your breath. In Catalan folklore—of pooping Christmas log fame—it's a giant dog or cat that enters your room and sits on your chest while you sleep. (Catalan folklore is the best.) But, usually, it's some variation of witch or demon suffocating and otherwise torturing the victim.
There's even a Swedish horror movie about the phenomenon.
Sleep paralysis is, crudely, your brain waking up before your body. You're lucid and awake upstairs, but your body mostly doesn't work. A distinguishing feature of the phenomenon is the feeling that you're breathing with a brick wall collapsed on your chest. Some movement is actually possible, but, again, it's like pushing against a pile of bricks. Nonetheless, I've succeeded in rolling myself onto the floor more times than I can count. Oddly enough, that never seemed to end the sleep paralysis and, more often, the phenomenon ended with falling back asleep fully and waking up 100 percent (brain and body) some short time later. The dreams that can occur in the gap between sleep paralysis episodes and waking up fully are absolutely beyond dreams—hallucinations, out-of-body experiences, Nightmare on Elm Street stuff.
What's weird is that over those years I never talked to a doctor about the experience. Granted, I tend to put off talking to doctors until situations are totally out of control, which was particularly true in my late-teens and early-20s. But looking back on it I have a hard time understanding why waking up dead every morning didn't prompt me to some action.
This reluctance probably has to do with sleep paralysis feeling beyond doctors. With my various maladies over the years, it's usually been possible at some point in the experience to pull away and take a cool, objective look at the situation. Less so with sleep paralysis; it happens in a state that feels, from one perspective, personal beyond medicine (as dreams often are); from a second perspective, the experience feels like something beyond correction. By both of these things, I think I mean that sleep paralysis feels like it has no objective life. The experience is defined by a complete inability to interact with the objective world, while still being forced to exist within it. That is the most personal thing I can think of and, as such, doesn't make sense in the same context as medical intervention, at least in the usual way.
That sounds pretty loopy and unscientific and if you've read anything else I've ever written for this site that might seem fishy. Well, it is that odd of a feeling.
Science sort of agrees. Sleep paralysis is considered a parasomnia, e.g. a sleep disorder that involves doing something generally weird. Other examples include sleepwalking, sleep sex, and sleep eating. Sleep dying stands out even among these, though they're all connected by the condition of "partial arousal" or waking up only partway (which takes many forms among the different stages of sleep). Sleepwalking, for example, is the opposite of sleep paralysis. The person's brain stays asleep while their body is awake or unparalyzed. (By the by, how weird is it that your brain can just flip a switch and shut off your ability to move?) Sleepwalking, perhaps because it has a much higher potential for consequences is much, much more studied, while its inverse remains the realm of folklore and blog posts.
A 2012 study in the journal Consciousness and Cognition attempts to tie centuries of "remarkably consistent" folklore surrounding sleep paralysis folklore to sleep neurophysiology. That is, there's more to the connection than just sleep paralysis phenomenon causing enough terror to lead its victims to conjure the supernatural. The unique sensation of "being ridden by the witch" traces nicely enough to real-world brain stuff. For one, sleep paralysis induces a "hypervigilant" state in the brain. This is a fairly specific condition in which a person goes into an extreme alert mode where all of their senses become super-sensitive. The result is wildly exaggerated real-world stimuli. It's a diagnostic criterion for PTSD and, as the resulting anxiety ramps up, delusions and hallucinations set in. According to the paper, this is the witch, the other person with you in the room sucking the breath out of your chest.
Actually, hypervigilance accounts for only the witch, not the breath-sucking. That sensation traces to a second factor. This factor is, in biospeak, due to hyperpolarization of motoneurons. In other words, it becomes more difficult to transmit a signal down a pathway of motor neurons (the ones that control muscle movement) because of an increase in the electrical potential between different neurons. It takes more spark to get the brain's message where it needs to go, like your diaphragm muscles.
This is what happens normally when you're in the REM (rapid eye movement) stage of sleep. After all, breathing is usually an unconscious reflex anyway; you don't need to fire messages from your conscious brain to your diaphragm to make respiration work. It just happens. Sensors around your heart detect changes in blood pH due to increase and decreases in carbon dioxide (see above), and fire messages to your brain's respiratory center in the Medulla oblongata, which fires the appropriate messages back down to your lungs. It's all pretty neat.
Anyhow, that's the unbearable crushing on your chest. Your body has naturally shut its motoneurons down because you're supposed to be asleep anyway and it doesn't want you acting out dreams. But in sleep paralysis it's only half-asleep, a collision of the REM sleep stages (body paralyzed, brain unconscious, dreams) and wakefulness, two stages bridged by NREM sleep (non-rapid eye movement, no dreams). NREM, partially characterized by the body not being paralyzed, itself has different stages, the first one of which involves the transition from waking thought to unconsciousness. In sleep paralysis, it's an overlap of these stages; the body is still paralyzed as in REM sleep but the brain is kicking out alpha waves, the signal that wakefulness has arrived. In consciousness, alpha waves are associated with resting or relaxing, while beta waves are associated with focus and, crucially, the body's stress responses. The first neurophysiological study of sleep paralysis, done by Takeuchi et al only 20 years ago, found that even beta waves were intruding into sleep. This isn't a thing that happens ever in normal sleep. Beta waves mean full-on awake.
Risk factors for sleep paralysis mostly involve brain chemicals and sleep habits: depression, anxiety, traumatic events/PTSD, and sleep disruption. At the time of my own sleep paralysis episodes, I was working graveyard shifts at a hotel while going to school during the day. For me, sleep happened usually between six and ten at night or for an hour around five in the morning on the floor of an office accompanied by a pillow and blanket I kept stashed in a file cabinet. It was pretty uncomfortable and, generally speaking, I was a psychiatric trainwreck made worse because of switching on and off medications all of the damn time. Maybe that's part of why I never raced to the doctor: I was a wasteland anyhow and, at the time, waking up dead seemed pretty reasonable.
It's totally amazing and cathartic (in a way) when sleep paralysis lifts. Usually, there's another stage of normal sleep afterward and, eventually, normal unparalyzed wakefulness. It's the most powerful whoosh of relief you can imagine—like taking your hand out of a fire—followed by several hours of scraped-out total exhaustion. It's a good feeling, a suffocating firestorm to purify or whatever. I would never recommend it.
A previous version of this story appeared on Motherboard in 2013.