Alicia Roth, PhD, provides a Q&A perspective on the science between 2 terrifying, sleep-related events.
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It’s a horrific feeling: you wake up in the middle of the night and are fully aware of your surroundings – but you can’t move. You’re paralyzed. And as the seconds tick by, you become more and more frightened until you fall back asleep or slowly gain movement again.
Or maybe you wake up and perceive there’s a presence in the room, something meant to harm you or threaten you, filling you with terror before, again, you drift back to sleep.
These instances – sleep paralysis and sleep hallucinations (also referred to as “sleep demons”) – can be incredibly scary things to experience. And, yet, aside from the fright, they’re harmless. They’re simply the results of disrupted sleep.
Still, that doesn’t help quell the fear when they happen. We talked to sleep disorder specialist Alicia Roth, PhD, about what causes these conditions and what you should know if you ever experience them.
The first component of this is sleep paralysis, a condition when a person wakes up but is temporarily unable to move. When it happens, it can feel absolutely terrifying but, Dr. Roth assures us, it is a completely benign condition.
“This happens when there’s a malfunction between REM (rapid eye movement) sleep and wakefulness,” says Dr. Roth. These occurrences, she says, affect about 10% of the population.
Not to be confused with deep sleep, REM sleep is a point in your sleep cycle when your brain is very active. So active, Dr. Roth says, “If we looked at your brain activity on a polysomnography (PSG) during REM sleep, it would look a lot like it does when you’re awake.”
“There are a lot of different things passing through your mind during REM sleep, some of which you remember as dreams,” she continues. “And one of the ways our bodies protect us during this period of REM sleep is to paralyze us so that we don’t act these things out in our sleep.”
For those who experience sleep paralysis, the problem comes when there’s a disruption in that transition between REM sleep and waking. “You’re consciously waking up, but that protective paralysis from REM sleep hasn’t fully subsided yet,” Dr. Roth explains.
For this reason, most people who experience sleep paralysis do so towards morning. But, Dr. Roth notes, it’s possible to experience it at any time.
Or something like them, something scary.
Just as sleep paralysis occurs when there’s a disruption in your sleep cycle, so, too, is it possible to have your sleep cycle interrupted in a way that you experience vivid dream-like hallucinations or your dream-state brain interprets something real as something altogether different. For instance, you might mistake your cat sleeping at the foot of the bed as some sort of goblin.
While many experience them when waking up (called hypnopompic hallucinations), it’s all possible to experience them while in the act of falling asleep (hypnagogic hallucinations). “Again, REM sleep is a very active time,” Dr. Roth notes, “and your brain is bringing that dream state to wakefulness.”
“These hallucinations aren’t dreams, though,” she clarifies. “You’re conscious but it’s another overlap between sleep and wakefulness.”
They’re also not necessarily always visual, she adds. “Most people experience them visually but they can be tactile, kinetic, olfactory or auditory.”
These hallucinations don’t necessarily manifest as demons, Dr. Roth says. Sometimes it can be a visual cue, as previously mentioned, or it could be something else. “Some people describe it as something scary or unsettling, knowing something is in the room with them. It’s more like a kinetic hallucination,” she says.
As for where the common reference to these hallucinations as “demons” comes from, Dr. Roth says that has more to do with the history of each culture and the ways in which these events have been interpreted through the (many, many) years.
“Going back even to what we’d consider ancient times, every culture has a version of this,” she says. “They each have this version of the idea of some scary entity sitting on your chest, something terrifying.”
Those experiences than get filtered, over time, through those cultural lenses as well as each person’s individual experiences. “Culture is really important when it comes to how each person perceives these hallucinations,” she adds.
While sleep paralysis and sleep hallucinations are two different events that occur separately, they can occur together. “A lot of people who report hallucinations say they experience sleep paralysis, as well,” Dr. Roth says. “It’s hard to predict when or why it happens.”
It’s certainly a recipe for a truly terrifying experience, a literal waking nightmare. You feel like you’re trapped and at the mercy of whatever scary monster is about to hurt you. But as horrifying as it feels at the time, again, you’re ultimately at no risk of harm, says Dr. Roth.
While we know the biological causes of these terrifying occurrences, but what causes these disruptions in sleep? According to Dr. Roth, there are a few factors that fuel these nighttime terrors.
A neurological disorder that can affect the brain’s control of sleep and wakefulness, narcolepsy can include periods of excessive daytime sleepiness and even instances in which a person has no control over falling asleep, even in the middle of the day or activity.
Sleep paralysis can often by a symptom of narcolepsy, Dr. Roth says. “When people are diagnosed with narcolepsy, they’re told to expect to have those paralysis episodes.”
Stress and other factors may not be a direct cause of these events but, Dr. Roth says, they can certainly play a factor in disrupting your sleep and making you more susceptible to having these experiences.
"When I work with patients, many of them are going through other sleep issues like insomnia or they’re not sleeping well in general,” she says. “They’re stressed or anxious about other things going on in life and that throws everything off.”
Again, Dr. Roth reminds us that these events are not indications of anything more serious. “In the moment, you’re not able to process it properly,” she says. “But it doesn’t necessarily mean that you have a mental health disorder or that there’s some degenerative disease process happening.”
She notes the recent increase in nightmares and stress dreams and ties them to the ongoing COVID-19 pandemic. “Think about what we’re all going through. Even if you aren’t a frontline worker, even if you’re not ill, your life has still been turned upside-down.”
If sleep paralysis and hallucinations are occurring for you, she says you should assess what big changes have been going on in your life. “Is there something you’re not dealing with well but is showing up in your sleep?” she asks.
Making sure you’re getting enough sleep, making sure you’re sufficiently rested and have health sleep habits are other aspects to consider.
“If you’re having these hypnagogic hallucinations as you transition from being awake to sleep, consider what you’re consuming before bedtime,” she says. “You need to turn off the news by 9 p.m. and you need to get away from social media by a certain time.”
While it might not seem like anything’s wrong in the moment, she says, what you prime your brain with before you fall asleep can have a dramatic impact on how you actually sleep and if there’s any disruption.
The less anxious input you have, the better your chances of getting through the night with your sleep uninterrupted.