Overview of Hypnagogic Hallucinations

Symptoms, Causes, Diagnosis, and Treatment of the Condition

A woman sleeping in her bedroom may fall asleep and experience hypnagogic hallucinations due to narcolepsy
Credit: Tetra Images / Getty Images

It can be pretty scary to hallucinate something while you are trying to fall asleep. These dream-like sensations may occur more commonly in certain scenarios. What is the definition of a hypnagogic hallucination? Learn more about the symptoms, causes, diagnosis, and treatment of these sensations and their connection to sleep with this overview.

Symptoms of Hypnagogic Hallucinations

A hypnagogic hallucination is a vivid, dream-like sensation that an individual hears, sees, feels or even smells and that occurs near the onset of sleep. As the individual falls asleep, for example, he experiences intense hypnagogic hallucinations and imagines that there are other people in his room. These episodes are usually brief and may also occur as someone transitions from slumber to wakefulness (a variant called hypnopompia). 

"Illusions occur while awake, and are classified as a sensory misrepresentation of an external stimulus, while hallucinations occur in the absence of any external stimuli," according to the American Sleep Association.

The ASA notes that these hallucinations are common, with at least 10 percent of the population experiencing such sensations. Teens, young adults and girls, and women are most likely to have these hallucinations.

Causes

It is possible for these episodes to occur sporadically and this may not be significant. Sometimes, hypnagogic hallucinations can indicate a problem. If they occur frequently, they may be upsetting and the disturbed sleep may lead to insomnia. There are a handful of potential causes that should be ruled out, including:

  • Medications
  • Alcohol near bedtime
  • Illegal drug use
  • Untreated anxiety

Other causes of sleep fragmentation, including sleep deprivation, irregular sleep patterns, or other sleep disorders may also be considered. In particular, hypnagogic hallucinations are one of the four cardinal symptoms of the sleep disorder narcolepsy.

Oftentimes hypnagogic hallucinations and sleep paralysis go hand in hand. During sleep paralysis, a person is immobile, unable to move, despite being conscious. This state occurs when people are transitioning between sleep and wakefulness and can cause an individual to be fearful.

It may be difficult for the person to realize the paralysis is fleeting. During a sleep paralysis episode, a person may struggle to breathe or feel muscle tightness. Sleep paralysis most often occurs when a person is waking up from sleep (hypnopompia) rather than when a person is drifting off to sleep (hypnagogia). 

Diagnosis

If you think you are suffering from hypnagogic hallucinations, or your loved ones think you are, talk to your doctor about the potential causes of these episodes. You may need to be referred to a board-certified sleep specialist or observed for further evaluation. Testing may require a diagnostic polysomnogram and multiple sleep latency testing (MSLT), with a stay at a sleep center.

If these hallucinations don't appear to be causing major disruptions to your life or sleep, no further action may need to be taken. However, it may be wise for you and your loved ones to familiarize yourselves with these hallucinations, so that you all feel a greater sense of control over them when they do occur.

Narcolepsy is a neurological disorder that occurs when the brain fails to effectively regulate sleep-wake cycles. It may be associated with recurrent hypnagogic hallucinations. Narcolepsy can lead to a person feeling excessively sleepy during the day. It may cause an irresistible urge to fall asleep during typical waking hours. Accordingly, narcolepsy is commonly associated with "excessive uncontrollable daytime sleepiness."

It may be associated with other symptoms, including cataplexy. Cataplexy is weakness associated with an emotion. For example, laughing, feeling scared, or telling a joke may prompt a sudden, transient weakness. This weakness may manifest as knees buckling, head drooping forward, weakness in hands, or even slurring of speech. It is also rare, affecting about 1 in 2,000 people. This means that there are fewer than 200,000 cases present in the U.S. population. Narcolepsy is a permanent condition and may require treatment with prescription medications for years.

Treatment

Infrequent hypnagogic hallucinations do not require treatment and simple reassurance may be enough. If a cause can be identified, eliminating it may be the most effective solution. The treatment of hypnagogic hallucinations may depend on behavioral changes and the use of medications that stabilize sleep. It is important to keep a regular sleep-wake schedule with a consistent wake time and bedtime. There should be an adequate amount of time spend in bed to meet your sleep needs. Sleep deprivation should be avoided. In the case of narcolepsy, medications that enhance sleep stability such as sodium oxybate (Xyrem) may be prescribed.

A Word From Verywell

Hypnagogic hallucinations may occasionally occur with no consequence. If recurrent and bothersome, and associated with other symptoms suggestive of narcolepsy, further evaluation by a board-certified sleep physician is recommended. Treatment may provide effective relief and make the transition to sleep easier.

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Article Sources
  • American Academy of Sleep Medicine. International classification of sleep disorders, 3rd ed. Darien, IL: American Academy of Sleep Medicine, 2014.

  • Kryger, MH et al. "Principles and Practice of Sleep Medicine." ExpertConsult, 6th edition, 2016.

  • Waters, F et al. "What is the Link Between Hallucinations, Dreams, and Hypnagogic-Hypnopompic Experiences?" Schizophr Bull. 2016 Sep;42(5):1098-109. doi: 10.1093/schbul/sbw076. Epub 2016 Jun 29.