Hypnagogia is the transition period between wakefulness and sleep. Sometimes people may see, hear and feel things that don’t exist during the hypnagogia phase – these are called hypnagogic hallucinations. Similar to lucid dreaming and sleep paralysis, scientific researchers think that hypnagogic hallucinations are related to REM sleep, the stage of sleep most associated with dreaming.
We’ve discussed some of the symptoms, causes, and mechanisms of hypnagogic hallucinations so you can better understand why and how they might occur.
What Are Hypnagogic Hallucinations?
The term hypnagogic was coined by the French physician Alfred Maury in 1848. Consisting of the Greek words “hypno”, meaning to sleep, and “agogos” meaning induced, the hypnagogic state describes the state of consciousness during the onset of sleep. The term hypnopompic was coined soon afterward and describes the onset of wakefulness.
Hallucinations are defined as sensory experiences that happen in absence of stimulation by the relevant sensory organs. These include:
- Visual hallucinations: seeing things, such as people, colors, and shapes, that aren’t present
- Auditory hallucinations: hearing voices and sounds that have no physical origin
- Tactile/physical: feeling physical sensations on the body surface when nothing is stimulating the skin or feeling motion in the body when it is still
- Olfactory: smelling things that have no physical origin
- Gustatory: having a taste in the mouth that has no physical source
Hallucinations sometimes appear in hypnagogic and hypnopompic states. These hallucinations are separate from the types of hallucinations that happen in dreams. Hallucinations in a hypnagogic state may seem more real than hallucinations in dreams. As such, they can be more disturbing for people.
Hypnagogic hallucinations may appear spontaneously with no apparent cause. Scientific data suggests that hypnagogic hallucinations are relatively common. In the UK, an estimated third of the population experience hypnagogic hallucinations. A sample study from the US showed 25% of participants experienced hypnagogic hallucinations, and these hallucinations were more common in women and younger age groups.
What Causes Hypnagogic Hallucinations?
Biology of Hypnagogic Hallucinations
Hypnagogic hallucinations may happen for a variety of different reasons. However, it’s likely that REM sleep plays an important role.
During sleep, the brain moves through a series of different stages. The sleep stage associated with dreaming is called rapid eye movement (REM) sleep.
Research has shown there is similar brain activity between REM sleep and hypnagogic hallucinations.
Many scientists believe that hypnagogic hallucinations can be caused by REM sleep intruding into wakefulness.
In support of this theory, research has shown there is similar brain activity between REM and hypnagogic hallucinations. For example, during both REM and hypnagogic hallucinations – an area of the brain called the thalamus is more strongly activated, and there is an increase of the chemical messenger acetylcholine.
Risk factors linked to hypnagogic hallucinations are:
- Substances, including cannabis and alcohol
- Sleep disorders – hypnagogic hallucinations are key symptoms of narcolepsy
- Nervous system diseases – sleep disruption and hallucinations can be symptoms of behavior and mood disorders
- Stress and anxiety
Disorders Associated with Narcolepsy
Hypnagogic hallucinations may present as a symptom of an underlying pathological disorder. As such, if hypnagogic hallucinations appear alongside other symptoms – it’s essential to seek specialist medical attention from a doctor.
Hypnagogic hallucinations may be a result of a sleep disorder. The sleep disorder most commonly associated with hypnagogic hallucinations is narcolepsy.
For most people, the sleep cycle begins with non-REM (NREM) sleep, then REM sleep follows. However, in people with narcolepsy, REM sleep can happen instantaneously in both sleeping and waking states. This effect means narcoleptic patients may uncontrollably fall asleep into REM during the day.
As well as hallucinations, people with narcolepsy commonly experience sleep paralysis (see below) and excessive daytime sleepiness.
Other Disorders Associated with Hallucinations
Common pathological disorders associated with hallucinations include schizophrenia, Parkinson’s disease (PD), and Charles Bonnet syndrome (CBS).
Schizophrenia is primarily a thought disorder. Schizophrenic hallucinations are most commonly auditory, and other symptoms include confused thought, delusions (false beliefs), and difficulties with problem-solving.
PD is primarily a movement disorder, and hallucinations are most commonly visual and auditory. Other symptoms include reduced movement, stiffness, and involuntary shaking.
CBS is an eye disease where visual hallucinations commonly occur as a result of vision loss. CBS hallucinations are usually simple and consist of shapes, lines, and colors.
Symptoms of Hypnagogic Hallucinations
Visual hallucinations make up most hypnagogic hallucinations, with an estimated 86% of all reported hypnagogic hallucinations being visual. Common hypnagogic visual hallucinations include kaleidoscopic geometric patterns, shapes, and flashes of light.
Physical sensations are the second most common hypnagogic hallucinations, occurring in 25-44% of cases. Common hallucinatory sensations include feelings of weightlessness, flying, or sensing the presence of somebody else.
Auditory hallucinations associated with hypnagogia include environment-related sounds, animal sounds, and people talking.
Lucid Dreaming & Sleep Paralysis
Lucid dreaming and sleep paralysis are separate from hypnagogic hallucinations but are both phenomena that commonly happen in the hypnagogic and hypnopompic states (between wakefulness and sleep).
Lucid dreaming is the awareness that one is dreaming while in an ongoing sleep. Research shows that people’s brain patterns when lucid dreaming is similar to REM sleep.
Lucid dreaming can have several benefits. Some people report it helps decrease anxiety and improves creativity and problem-solving skills. People also use lucid dreaming as a way to help control nightmares.
In REM sleep, the muscles temporarily lose function. However, sometimes REM muscle function loss can happen between sleeping and waking states while people are still conscious. This phenomenon is called sleep paralysis.
Sleep paralysis can sometimes be scary. Some common feelings that often happen alongside sleep paralysis are being pressed down on or non-existent figures being present in the room.
Having disrupted sleep and a lack of sleep increases the likelihood of sleep paralysis.
How are Hypnagogic Hallucinations Treated?
If somebody is experiencing frequent hypnagogic hallucinations, they may choose to go to a sleep specialist to determine whether the hallucinations are happening due to a sleep disorder, such as narcolepsy.
Sleep specialists will use a test called polysomnography to diagnose sleep disorders. Polysomnography measures people’s brain waves, eye and leg movements, and blood oxygen during sleep.
Consulting with a doctor can determine whether hypnagogic hallucinations are occurring as part of an underlying condition.
As hypnagogic hallucinations can present as a symptom for nervous system disorders, like schizophrenia, PD, or CBS, consulting with a doctor can determine whether the hallucinations are occurring as part of an underlying condition. The diagnosis will help doctors to prescribe appropriate medications and therapy treatments.
Infrequent hypnagogic hallucinations rarely have adverse outcomes. As such, stand-alone or occasional hypnagogic hallucinations don’t require treatment.
Having a regular sleeping pattern and adequate sleep will likely decrease the chance of hypnagogic hallucinations occurring. The National Sleep Foundation guidelines suggest that adults need between 7-9 hours of sleep per night.
Summary on Hypnagogic Hallucinations
Hypnagogic hallucinations may happen due to a pathological condition and can also happen spontaneously without a clear cause, although it’s likely REM sleep plays a role.
If you are experiencing regular hypnagogic hallucinations, it’s important to determine whether this could be linked to an underlying condition, such as schizophrenia. Speaking to a sleep specialist can also help determine whether these hallucinations are because of a sleep disorder such as narcolepsy.
Generally speaking, hypnagogic hallucinations don’t have adverse effects, and infrequent hypnagogic hallucinations are relatively common. However, if you want to decrease the risk of hypnagogic hallucinations occurring, ensuring good sleep hygiene and reducing cannabis and alcohol intake will help.