Sleep Paralysis: Why It Happens and How to Stop It

What Is Sleep Paralysis?

Sleep paralysis is a state of temporary muscle paralysis that occurs at the boundary between sleep and wakefulness — either when falling asleep (hypnagogic) or upon waking up (hypnopompic). Consciousness is fully present, but the body cannot move. The core mechanism is REM atonia: during REM sleep, the brain paralyzes skeletal muscles to prevent you from acting out your dreams. Neurophysiological research shows that this inhibition is mediated by glutamatergic neurons in the subcoeruleus nucleus (SLD), which activate GABA/glycinergic neurons in the ventromedial medulla to suppress spinal motor neurons (Luppi et al., Frontiers in Neurology, 2015). Normally, this paralysis lifts when REM ends. Sleep paralysis occurs when the REM atonia persists into wakefulness — the motor inhibition outlasts the sleep state that caused it.

A systematic review by Sharpless and Barber (2011), pooling data from 36,533 participants across 35 studies, found that approximately 7.6% of the general population experience at least one episode of sleep paralysis in their lifetime. Among students, the rate was 28.3%; among psychiatric patients, 31.9%. Sleep paralysis is far more common than most people realize.

Episodes typically resolve on their own within seconds to a few minutes. Accompanying symptoms can include difficulty breathing, a feeling of chest pressure, and vivid hallucinations. Attempts to force movement or cry out often feel impossible and can heighten panic, making the episode feel longer than it is.

Why Sleep Paralysis Happens

The direct cause of sleep paralysis is a failed transition between REM sleep and wakefulness. Neurophysiologically, REM atonia is driven by the subcoeruleus nucleus (SLD nucleus), which inhibits spinal motor neurons through GABA and glycine neurotransmitters. When this inhibitory signal persists after REM ends, sleep paralysis occurs.

Several factors make this timing error more likely:

• Sleep deprivation — When sleep-deprived, the brain compensates with REM rebound during recovery sleep, which destabilizes the REM-wake transition.
• Irregular sleep schedule — Disrupting the circadian rhythm destabilizes REM sleep timing. Shift workers and those experiencing jet lag report elevated rates.
• Supine sleeping position — Studies show the majority of sleep paralysis episodes occur in the supine position, at a rate 3–4 times higher than other positions.
• Stress and anxiety — High psychological stress disrupts sleep architecture and increases REM instability.
• Narcolepsy — Sleep paralysis is one of the four classic features of narcolepsy, in which the REM regulation mechanism itself is impaired.

Genetic predisposition also plays a role. A twin and molecular genetics study by Denis et al. (Journal of Sleep Research, 2015), analyzing 862 participants, estimated a genetic contribution of approximately 53% to sleep paralysis susceptibility and identified associations with variants in the PER2 circadian gene. Additional research has identified associations with genetic variants linked to REM sleep architecture.

The Hallucination Component: The Science Behind the 'Demon'

A significant proportion of sleep paralysis sufferers report vivid hallucinations. These fall into three main types: intruder hallucinations (a sense that someone is in the room), vestibular-motor hallucinations (floating, flying, or out-of-body sensations), and incubus hallucinations (a heavy pressure on the chest combined with breathing difficulty). It is the incubus hallucination, in particular, that underlies the universal cross-cultural experience of a 'demon sitting on the chest.'

Cheyne, Rueffer, and Newby-Clark (1999) analyzed the neurological and cultural construction of sleep paralysis hallucinations, proposing that they result from the combination of active REM dream-generation circuits and intense amygdala hyperactivation during wakefulness. The amygdala — the brain's threat-detection center — receives a powerful threat signal from the paralysis itself, which generates the image of a dangerous intruder.

This explains why sleep paralysis experiences are strikingly consistent across cultures and throughout history. Medieval Europeans described incubi sitting on sleepers' chests; Japanese tradition calls it kanashibari (bound in metal); West African folklore describes the Old Hag; and countless other cultural frameworks name the same neurological phenomenon. Research by Hinton et al. (Transcultural Psychiatry, 2005) among Cambodian refugees confirmed this pattern — 67% of PTSD patients experienced sleep paralysis, and hallucination content universally followed the threatening-presence template. Because the amygdala's threat-processing mechanism is universal, the resulting hallucination has a universal shape — a threatening presence bearing down on the sleeper.

The good news is that the hallucinations, terrifying as they feel, are completely harmless. They are perceptions generated by the brain's dream circuitry — not reality.

Risk Factors for Sleep Paralysis

Anyone can experience sleep paralysis, but the following factors increase the likelihood of recurrence:

• Irregular sleep schedule — Shift work, night shifts, and frequent time zone changes reduce REM sleep stability. Irregular sleep timing is one of the strongest predictors of sleep paralysis.
• Chronic sleep deprivation — Consistently sleeping less than recommended hours amplifies REM rebound, increasing sleep paralysis frequency.
• Stress and anxiety disorders — Sleep anxiety increases sleep fragmentation and REM instability, raising the incidence of sleep paralysis.
• PTSD and psychiatric conditions — PTSD and panic disorder are associated with significantly elevated rates of sleep paralysis. Research indicates sleep paralysis rates of 27.8–67% in individuals with PTSD (Sharpless & Barber, 2011).
• Supine sleep position — Sleeping flat on your back is consistently reported to increase both the frequency and intensity of episodes.
• Family history — Sleep paralysis has a heritable component; a family history of episodes increases individual risk.

How to Reduce Sleep Paralysis Episodes

There is no single cure for sleep paralysis, but research supports the following approaches for reducing episode frequency:

1. Maintain a Consistent Sleep Schedule

The brain relies on routine to regulate REM sleep. Sleeping and waking at the same time every day is the most fundamental strategy for stabilizing REM sleep and reducing sleep paralysis risk. Review our sleep hygiene checklist for a comprehensive approach to improving your sleep routine.

2. Change Your Sleep Position

Avoiding the supine position is one of the most actionable changes you can make. A large study by Cheyne (Journal of Sleep Research, 2002) involving 6,730 participants found that sleep paralysis episodes occur 3–4 times more frequently in the supine position, and more episodes were reported in the supine position than in all other positions combined. Learn more about optimal sleep positions. Side sleeping is recommended; placing a pillow behind your back can help prevent unconscious rolling into the supine position.

3. Address Sleep Deprivation

Chronic sleep deprivation is one of the strongest triggers for sleep paralysis. Ensuring adequate sleep duration is critical. To understand how much sleep you actually need, read our guide on how many hours of sleep you need.

4. Manage Stress and Anxiety

High stress and anxiety disrupt sleep architecture. A pre-bed relaxation routine — including progressive muscle relaxation or breathing exercises — may help reduce episode frequency. If sleep anxiety is a contributing factor, see our article on how to break the cycle of sleep anxiety.

5. What to Do During an Episode

Panicking during an episode tends to prolong the perceived duration. Instead, try: (1) remind yourself that this is sleep paralysis and it will end soon; (2) focus on initiating a very small movement in your fingers or toes rather than trying to move your whole body; (3) rapid eye movements or deliberately closing and opening your eyes may help break the paralysis; (4) use controlled breathing to reduce the panic response.

When to See a Doctor

In most cases, sleep paralysis improves with lifestyle changes alone, without medical treatment. However, consult a doctor or sleep specialist if:

• Episodes recur more than once a week and interfere with daily functioning, including daytime concentration or work performance.
• Sleep paralysis is accompanied by excessive daytime sleepiness.
• Cataplexy — sudden loss of muscle tone triggered by strong emotions like laughter — or sleep attacks (sudden, irresistible sleep onset) are also present. These are hallmarks of narcolepsy, which requires dedicated evaluation.
• Episodes cause significant psychological distress or sleep phobia, leading to sleep avoidance.

A physician can evaluate for narcolepsy using the Multiple Sleep Latency Test (MSLT). For confirmed recurrent isolated sleep paralysis (RISP), medications that suppress REM sleep — such as tricyclic antidepressants or SSRIs — may be used depending on the underlying cause. A clinician's guide by Sharpless (Neuropsychiatric Disease and Treatment, 2016) outlines a short-term CBT-based treatment (5 sessions) combining sleep hygiene, relaxation techniques, and cognitive restructuring as effective for reducing both episode frequency and fear responses. Many patients find that understanding the benign nature of sleep paralysis significantly reduces both the fear response and episode frequency.

References

• Sharpless, B. A., & Barber, J. P. (2011). Lifetime prevalence rates of sleep paralysis: A systematic review. Sleep Medicine Reviews, 15(5), 311–315.
• Cheyne, J. A., Rueffer, S. D., & Newby-Clark, I. R. (1999). Hypnagogic and hypnopompic hallucinations during sleep paralysis: Neurological and cultural construction of the night-mare. Consciousness and Cognition, 8(3), 319–337.
• Cheyne, J. A. (2002). Situational factors affecting sleep paralysis and associated hallucinations: Position and timing effects. Journal of Sleep Research, 11(2), 169–177.
• Denis, D., French, C. C., Rowe, R., Zavos, H. M. S., Nolan, P. M., Parsons, M. J., & Gregory, A. M. (2015). A twin and molecular genetics study of sleep paralysis and associated factors. Journal of Sleep Research, 24(4), 438–446.
• Luppi, P. H., Peyron, C., & Fort, P. (2015). Not a single but multiple populations of GABAergic neurons control sleep. Frontiers in Neurology, 6, 90. (Overview of REM atonia circuitry)
• Hinton, D. E., Pich, V., Chhean, D., Pollack, M. H., & McNally, R. J. (2005). Sleep paralysis among Cambodian refugees: Association with PTSD diagnosis and severity. Depression and Anxiety, 22(2), 47–51.
• Sharpless, B. A. (2016). A clinician's guide to recurrent isolated sleep paralysis. Neuropsychiatric Disease and Treatment, 12, 1761–1767.