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Hypnagogia: What Happens at the Edge of Sleep

Hypnagogic hallucinations are sights, sounds or sensations as you drift off. They're common and usually not a concern. What causes them and when to see a GP.

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Hypnagogia: What Happens at the Edge of Sleep

Hypnagogic hallucinations are sights, sounds or body sensations that appear as you drift off to sleep: a flash of shapes, a face, your name called out, a feeling of falling. They're common. Cleveland Clinic says they're usually not a cause for concern, and for most people they aren't linked to any health condition. Estimates of how many people get them vary. The American Academy of Sleep Medicine (AASM) says sleep-related hallucinations have been reported by as many as a third of people, and Cleveland Clinic says up to 70% of people have at least one.

The state they come from is called hypnagogia, the short stretch between being awake and being asleep. Below is what happens in it, what the hallucinations are like, when they're worth a GP visit, and what researchers have done with this in-between state.

What is hypnagogia?

Hypnagogia is the transition from wakefulness to sleep. Sleep researchers link it to stage 1 non-REM sleep (N1), the changeover from waking to sleep. The National Institute of Neurological Disorders and Stroke says that in this stage your breathing, heartbeat and eye movements slow, your muscles relax with occasional twitches, and your brain waves begin to slow. The Sleep Foundation says N1 usually lasts one to seven minutes. For what happens next, see what happens in each stage of sleep.

The mirror image, on the way out of sleep, is hypnopompia. Hallucinations as you wake up are called hypnopompic.

What do hypnagogic hallucinations feel like?

They're usually brief and fleeting, though occasionally they last longer. Cleveland Clinic lists these forms:

  • Visual. About 86% of hypnagogic hallucinations are visual. Most are changing geometric patterns, shapes and flashes of light, a bit like looking into a kaleidoscope. Some are images of animals, people or faces.
  • Body sensations. Between 25% and 44% involve the body: feeling distorted, weightless, flying or falling, or sensing that someone else is in the room.
  • Sounds. Between 8% and 34% are auditory. They can be words or your name, people talking, or everyday and animal sounds. The Sleep Foundation, which gives the same figures, adds music.

These shares are of hallucinations, not of people.

They aren't the same as dreams. Dreams usually have a storyline, while hypnagogic hallucinations tend to be brief images or sounds. You're still awake, if only just, so it can take a moment to work out what's real. The Sleep Foundation says people generally recognise them as hallucinations rather than taking them as real.

Hypnagogic vs hypnopompic hallucinations

HypnagogicHypnopompic
WhenAs you fall asleepAs you wake up
What they're likeMostly brief visual images; also sounds and body sensationsMostly visual too, according to the AASM, which also describes a rarer kind after a sudden waking, still images of people or animals that can last many minutes and tend to vanish when you turn on a light
Usually a concern?No, according to Cleveland ClinicNo, according to Cleveland Clinic

Those rarer waking images can feel real enough that people jump out of bed, and the AASM notes this can lead to injury.

What causes them?

Researchers aren't sure. Cleveland Clinic says they seem neurologically similar to both dreams and daytime hallucinations. An older idea was that they're bits of REM (dreaming) sleep breaking into waking, but the Sleep Foundation says current research doesn't back that up. A 2016 review compared sleep-related experiences with waking hallucinations in conditions such as Parkinson's disease and schizophrenia. It found considerable overlap in how people describe them and in the brain systems involved. The key differences are that sleep-related ones are immersive and largely cut off from the room around you, while waking hallucinations are separate events laid over normal perception, and that sleep-related ones involve only some of the same brain networks.

What's known is what makes them more likely. The Sleep Foundation lists stress, sleep deprivation and some medicines as triggers. Cleveland Clinic says they're more common in people with narcolepsy, insomnia, excessive daytime sleepiness or a mental health condition, and in people taking tricyclic antidepressants. The AASM adds current drug use, past alcohol use, anxiety, mood disorders and insomnia.

Sources differ on anxiety. Cleveland Clinic says it typically doesn't cause them, while the AASM lists anxiety among the factors that can. Either way, frequent or disturbing ones can make you anxious about going to sleep.

Are they normal or a sign of something?

For most people they aren't a sign of anything. Because they're so common, the Sleep Foundation says having them doesn't necessarily mean anything is wrong, and they usually don't have a major effect on a person's life.

They're also different from the hallucinations of conditions like schizophrenia, Alzheimer's disease or Parkinson's disease. Cleveland Clinic points out that people with those conditions have hallucinations during the day, when they're wide awake, alongside other significant symptoms.

Narcolepsy often comes up alongside these hallucinations, but it's a rare condition.

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See a GP if:

  • you also feel very sleepy in the day, fall asleep suddenly, or your muscles go weak when you laugh or feel a strong emotion (possible signs of narcolepsy)
  • you have hallucinations when you're fully awake, during the day or night
  • they started after you began a new medicine (tell your GP or pharmacist, and don't stop a prescribed medicine on your own)
  • they make you anxious about going to sleep, or often disturb your sleep

For ongoing sleep problems, CBT-I (cognitive behavioural therapy for insomnia) is the recommended first treatment. Ask your GP.

If you're struggling, talk to your GP. UK: Samaritans 116 123. US: 988.

This is general information, not medical advice. NSDR is not a treatment for any condition.

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Hallucinations and sleep paralysis

The AASM says sleep hallucinations and sleep paralysis can happen at the same time. If you were aware but couldn't move or speak during the experience, that's sleep paralysis, which the NHS describes as being unable to move or speak as you fall asleep or wake up. Our guide to sleep paralysis covers why it happens and what helps.

The jolt as you fall asleep (hypnic jerks)

A hypnic jerk, or sleep start, is a sudden, brief, strong jerk of the body or part of it as you fall asleep, sometimes with a feeling of falling. The AASM says sleep starts have been reported in 60% to 70% of people, are very common, and need no treatment in most people. Lots of caffeine or other stimulants, intense exercise beforehand, sleep loss and emotional stress can make them more frequent. See a sleep doctor if the jerks, or worry about them, keep you from getting enough sleep.

Can you use the hypnagogic state?

Researchers have tried. The results are early, and none of them is a technique you can rely on yet.

Problem-solving. In a 2021 Paris study, 103 healthy participants (average age about 23) worked on number puzzles that had a hidden shortcut. They then rested for 20 minutes, reclined in a dark room with their eyes closed, holding a bottle. Those who spent at least 15 seconds in N1 were about three times as likely to spot the shortcut afterwards (83% against 30% for those who stayed awake, which was 20 of 24 people against 15 of 49). The effect disappeared in people who went on into deeper sleep. The groups were formed by what happened during the rest, not assigned in advance. Holding the bottle was inspired by an anecdote about Thomas Edison, who supposedly napped while holding spheres in his hands. The authors say a test without the bottle is needed before anyone can say the trick itself helps. It's one lab task and a small group who reached N1, so read it as a promising finding, not a technique.

Steering the imagery. Researchers at MIT and Harvard built Dormio, a wearable that plays a spoken cue at sleep onset so the cued topic can turn up in hypnagogic dreams (Haar Horowitz et al. 2020). For now it's a research tool for studying dreams.

Replaying the game. In a 2000 study of 27 adults (aged 18 to 62), people who played Tetris reported images of the game as they fell asleep. So did three of the five people with amnesia from brain damage, who couldn't recall playing. That suggests this imagery may not depend on being able to remember the experience.

Yoga nidra. Yoga nidra ("yogic sleep") aims for deep relaxation that, unlike sleep, keeps some awareness of your surroundings. Swami Satyananda Saraswati shaped the modern practice from the 1960s. In a 2022 EEG study, 30 newcomers learned yoga nidra. After two weeks of practice, the sessions of the 26 who were analysed were scored as awake throughout, with patches of slow waves, often called "local sleep". So in beginners, yoga nidra was scored as wakefulness, not as N1, the stage most closely tied to hypnagogia, though with local slow-wave activity. For more, see what yoga nidra is.

Yoga nidra is the older yoga practice of guided, lying-down rest. NSDR is a close modern relative with less traditional language. See how they compare. The research is early. Four small trials have tested NSDR itself, with mixed results. A 2026 review of 73 yoga nidra studies found significant benefits for stress and anxiety, but its authors say the low study quality means those effects likely reflect inflated estimates.

How to make hypnagogic hallucinations less likely

They may not need any treatment, and the AASM says they tend to decrease with time. Both the AASM and Cleveland Clinic say they may become less frequent if you:

The Sleep Foundation adds general sleep habits: a dark, cool bedroom, less screen time before bed, and something to wind down stress, such as meditation. If it's hypnic jerks that bother you, avoiding caffeine and other stimulants is the AASM's suggestion.

FAQ

Can you have hypnagogic hallucinations during the day?

Yes, if you're falling asleep, because they happen as you drift off. Hallucinations while you're fully awake are different. The Sleep Foundation says daytime hallucinations need medical attention, and the AASM says sleep hallucinations during the day can be a sign of narcolepsy.

Can medication cause hypnagogic hallucinations?

Yes, some medicines are linked to them. Cleveland Clinic says they're more common in people taking tricyclic antidepressants, and the AASM lists medication use among possible causes. If they began with a new medicine, talk to your GP or pharmacist, who may adjust it. Don't stop a prescribed medicine on your own.

Is hypnagogia dangerous?

No, not for most people. Cleveland Clinic says hypnagogic hallucinations are relatively common and likely not something to worry about. One practical risk comes from the rarer vivid images on waking, which can make people leap out of bed. Worry is the other cost, which is why distressing or frequent episodes are worth raising with a GP.

What is hypnopompia?

Hypnopompia is the transition from sleep to waking, as hypnagogia is the transition into sleep. Hallucinations in it are called hypnopompic, and like hypnagogic ones they usually aren't a cause for concern.

Sources