What Causes Sleep-Related Hallucinations?

Simple Visual Hallucinations Commonly Occur with Sleep Transitions

A woman hallucinates after waking from sleep
A woman hallucinates after waking from sleep. Getty Images

Have you ever awakened from sleep and thought you were still dreaming? It is very common to have experienced hallucinations while falling asleep or after waking. Though mostly visual, there are a number of possible ways to experience these hallucinations, including with sleep deprivation. What causes sleep-related hallucinations? Learn about these phenomena and why they might occur.

Simple Hallucinations May Commonly Occur with Sleep Transitions

When people report hallucinations, they often describe visual experiences: seeing something that isn’t there or misinterpreting something in the environment (referred to as an illusion).

As an example, you might see bugs crawling on the ceiling or misinterpret the lamp as a shadowy figure standing in the room.

Though visual experiences predominate, some hallucinations may involve hearing things. These auditory hallucinations may range from voices to loud sounds or other stimuli. It is also possible to feel something with tactile hallucinations or even have a sense of movement with a kinetic hallucination.

Hallucinations that occur while falling asleep are called hypnagogic hallucinations. These most often occur due to the sudden onset of rapid eye movement (REM) sleep near sleep onset. When waking from REM sleep, which is more prevalent towards morning, hypnopompic hallucinations may occur.

No matter the type, hallucinations are surprisingly common. It is estimated that 25 to 37 percent of people have experienced hypnagogic hallucinations. Hypnopompic hallucinations affect 7 to 13 percent of people.

Hallucinations surrounding sleep seem to occur more among young people, especially in adolescence and young adulthood. They are also more frequently reported by women.

Hallucinations may be associated with other symptoms. They commonly coexist with sleep paralysis. The afflicted person may be startled and jump out of bed.

It may be seen with other sleep-related behaviors, including sleepwalking and sleep talking. Hallucinations can also occur independently during the daytime.

Complex Hallucinations May Represent Different Phenomena

More complex visual hallucinations that occur at night may represent a distinct experience. After a sudden awakening, without the recall of an associated dream, an affected person may hallucinate a complex and vivid visual scene. This may include people or animals that are distorted in size or shape. Though relatively immobile, it may seem real and be frightening. It may persist for many minutes. Though awake when it occurs, it may follow from non-REM sleep. The hallucination disappears as lights are turned on. These complex hallucinations seem to have unique causes and may be due to different medical conditions.

Causes of Sleep-Related Hallucinations

As noted above, hallucinations associated with sleep transitions occur at least occasionally in a high proportion of the general population.

It may simply represent the persistence of dream imagery into wakefulness. This results in an overlap state. It may be worsened due to sleep deprivation. This may be a normal phenomenon in sleep-wake transitions, but it can also be seen in some with other conditions.

These hallucinations occur commonly in narcolepsy. This condition is associated with fragmented sleep, excessive daytime sleepiness, sleep paralysis, and often cataplexy.

Complex hallucinations are somewhat rare and may suggest the presence of a neurologic or visual disorder. These may occur in Parkinson’s disease or dementia with Lewy bodies. When vision is lost, especially in blindness, the occipital lobe of the brain may create aberrant images. In effect, the brain begins to create visual ideas because of a lack of signal input from the eyes.

In addition, hallucinations can be associated with substance abuse, psychiatric illness, and other sleep disorders. Current or past alcohol or drug use may provoke hallucinations. Anxiety and other mood disorders, as well as schizophrenia, may evoke hallucinations. Insomnia, especially difficulty falling asleep, and insufficient sleep to meet needs may also provoke hallucinations. It is estimated that 80 percent of people will experience visual hallucinations if sleep deprived enough.

If persistent and bothersome, it is important to rule out other potential causes of hallucinations. Medical conditions like seizures and migraines should be excluded. The effects of medications or substance use should be considered. Psychiatric problems should be identified and treated. Other sleep disorders, including nightmares and exploding head syndrome as well as sleep paralysis, should be excluded.

When hallucinations surrounding sleep are problematic, speak with a sleep specialist about ways to relieve these symptoms. In some cases, simply understanding the phenomena is enough to ease the mind back to sleep.


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