Hypnagogic Hallucinations: What's Normal and Why

Seeing faces in the dark, hearing your name called or feeling yourself fall just as you drift off can be unsettling. And it gets worse when you look it up and find the word hallucination attached to it. But these flashes at the edge of sleep are among the most ordinary things the brain does, and in one large survey four people in five said they'd had them.^[1] They're called hypnagogic hallucinations, and for nearly everyone they're harmless. Here's what they are, why they happen, the few cases that are worth a doctor's visit, and how some people put them to use.

What are hypnagogic hallucinations?#

Hypnagogic hallucinations are images, sounds or bodily sensations that come as you're falling asleep, while part of you is still awake.^[2] The ones that come as you wake up are called hypnopompic hallucinations, and they're usually the end of a dream carrying on for the first seconds or minutes after you open your eyes. Both belong to the in-between state called hypnagogia, or the hypnagogic state, which is the first few minutes of the lightest stage of sleep.

It's an odd state from the inside, because you're no longer quite awake but not asleep either. People woken from it often insist they were awake the whole time. Sleep researchers describe it as half lucid, a state where you start to lose touch with the room but can still watch your own mind wander.^[3] And it explains why hypnagogic hallucinations feel so real, since you're conscious enough to notice them while your brain has already started to dream.

Hypnagogic hallucinations are also much more common than the hypnopompic kind. In a phone survey of almost 5,000 people in the UK, 37% had had hypnagogic hallucinations and 12.5% hypnopompic ones. Both were more common in people who slept badly or were sleepy during the day.^[4]

What do hypnagogic hallucinations look like?#

So what will you see, hear or feel? Most hypnagogic hallucinations are something you see, and visual experiences make up 86% of hypnagogia, and they're usually shifting patterns, shapes and flashes of light, though faces, animals and whole scenes come too, often lifelike, detailed and in colour. Sounds are rarer (8% to 34%, depending on the study), and they tend to be a word or your name, people talking, a phone or a doorbell. Then there are sensations in the body, reported in 25% to 44% of cases, from floating or falling to the feeling that someone else is in the room.

The falling feeling often ends in a jolt, a sudden twitch of the whole body that wakes you up just as you were going under. It's called a hypnic jerk, most of us have had one, and it's nothing to worry about. The presence in the room is another matter, because it overlaps with sleep paralysis, when you wake up unable to move. If that's what happened to you, the guide to the sleep paralysis demon explains it. Most hypnagogic hallucinations come with no paralysis at all, and you can open your eyes, move, and watch the image vanish.

Why do hypnagogic hallucinations happen?#

Once the fright has passed, most people want to know where the images came from, and part of the answer is surprisingly ordinary (your brain is going back over your day). When people played the video game Tetris for hours and were then asked what they saw as they dozed off, many described the same thing, little blocks falling and turning on a screen. Three patients with amnesia, who couldn't remember playing the game at all, saw similar images.^[5]

So the content comes from whatever your brain has been busy with, whether or not you remember it. How often you get them depends mostly on how you sleep, because they're more frequent when you have insomnia, when you're sleepy during the day, and when you're anxious or depressed.

Are hypnagogic hallucinations a sign of schizophrenia?#

Am I going mad? Is this how it starts? That's the fear behind a lot of late-night searches, and the answer is almost always no. In a survey of more than 13,000 people in the UK, Germany and Italy, a quarter had hypnagogic hallucinations, and in more than half of cases they had nothing to do with any illness.^[6] The hallucinations that did point to psychosis were the ones people had during the day, fully awake, and those were rare (3.2% of people saw things and 0.6% heard voices).

The two kinds of hallucination also feel different from the inside. Hallucinations at the edge of sleep rarely change what you believe about yourself or the world, and most of them stay in bed with you and have little effect on your day. If you've seen a figure as you drifted off and woke up worried about your mind, you can let that worry go, because the timing is the reassuring part.

Matteo Maretto, Unsplash

There's no switch to turn hypnagogic hallucinations off, but since they come more often with poor sleep, sleeping better is the best way to have fewer of them. Regular hours, enough of them and no coffee late in the day (sorry) do more than any trick (sleep hygiene habits has the ones that matter most). When one comes, open your eyes, sit up or switch on a small light, and it will fade.

When to see a doctor about hypnagogic hallucinations#

For most of us the answer is never, because nothing is wrong. But hypnagogic hallucinations are also one of the symptoms of narcolepsy, a long-term sleep disorder. The signs to watch for are severe sleepiness during the day that doesn't get better even when you've slept enough, and sudden muscle weakness brought on by strong emotions like laughter, fear or excitement.^[7] Sleep paralysis and broken nights are common with it, too.

Narcolepsy is rare, though, and hypnagogic hallucinations are far too common for it to explain more than a sliver of them. In the UK survey, narcolepsy affected 0.04% of people while 37% had the hallucinations. Do see a doctor if you have the signs above, if you hallucinate during the day while fully awake, or if the hallucinations are frequent and frightening enough to keep you from sleeping. A doctor may ask you to keep a sleep journal for a week or two, noting when you sleep and what happens. That's much easier if you already have the habit of recording your nights when you wake.

How to use the hypnagogic state#

Not everyone wants to get rid of these images, and writers and inventors have been curious about them for a long time. Edgar Allan Poe wrote about "fancies" that came to him only at the edge of sleep, and he noticed that he was aware of them while they came.^[8]

Thomas Edison is said to have napped holding balls in his hands, so that when he dozed off they'd fall and clatter and wake him with an idea. Researchers tested exactly that. They gave people a maths task with a hidden shortcut, then a 20-minute break to relax with their eyes closed, holding an object that would drop if they fell asleep. Those who drifted into the lightest stage of sleep (often for only a minute) found the shortcut far more often afterwards than those who stayed awake. But those who went deeper lost the benefit completely.

The falling object isn't a perfect alarm, as the same researchers found. Of the 63 times it dropped, only 26 came after the person had actually reached light sleep, so treat it as a rough guide rather than a timer. What people saw in those moments had the loose, sudden logic of a dream, and one participant woke with a start mid-climb.

If you'd like to try it, it only takes a quiet afternoon and something that makes a noise when it falls.

1. Wait until you feel naturally sleepy, after lunch or just before bed.
2. Sit or recline comfortably with your eyes closed, holding a bottle, a set of keys or a spoon above a plate.
3. Let yourself drift, and watch the images without chasing them or trying to hold on.
4. When the object drops, say or write down what was in your mind straight away, before it fades.

The same edge of sleep is where some lucid dreamers try to slip into a dream while staying aware, the idea behind the wake-induced techniques. And if you wonder where that leads, what lucid dreams are explains it. If you'd rather take a question to bed with you, dream incubation and using dreams for creativity go further.

Tonight, if a face or a voice turns up as you drift off, you don't have to push it away or lie there wondering what it means. Watch it for a moment and let it go when it goes, because it's only your brain tidying up after the day, and you'll be asleep before it's finished.