Sleep paralysis

Sleep Paralysis

TYPESleep phenomenon

FIELDSleep medicine, psychology

ALSO KNOWN ASREM intrusion

NOTABLE CASE(S)The Old Hag (Newfoundland folk tradition)

STATUSWell-established medical phenomenon

Sleep paralysis is a temporary inability to move or speak that occurs while falling asleep or waking up, often accompanied by vivid hallucinations. It is one of the best-understood non-paranormal explanations for reported sensed presences, shadow figures, and bedroom "ghost" sightings catalogued elsewhere on The Vault, and is covered here in its own right as a recognised sleep phenomenon, distinct from the general Hallucination page and the specific Newfoundland folk tradition covered under Old Hag.

Mechanism

During ordinary REM sleep, the brain produces "REM atonia" — a temporary relaxation of the body's voluntary muscles that prevents a person from physically acting out their dreams. Sleep paralysis occurs when this atonia persists briefly into a state of consciousness, either as a person is falling asleep or waking up, leaving them fully aware and able to breathe normally, but temporarily unable to move their limbs, body, or speak. Episodes typically last seconds to a few minutes, and usually end on their own, or when the person is touched, spoken to, or makes an intense effort to move.

Classification

Sleep specialists distinguish between isolated sleep paralysis, a one-off episode unconnected to any other sleep disorder, and recurrent sleep paralysis, involving repeated episodes over time. Where recurrent episodes occur in someone without narcolepsy, the condition is specifically termed recurrent isolated sleep paralysis (RISP).

Prevalence

Estimates of lifetime prevalence vary, with some reviews putting the general population figure at around 8%, rising substantially — to around 30–38% — among students and psychiatric patients. Close to half of people diagnosed with narcolepsy report experiencing sleep paralysis at least once.

Risk factors

Sleep paralysis is more likely with disrupted or fragmented sleep — including sleep deprivation, irregular schedules, jet lag, and shift work — as well as stress and certain mental health conditions, including anxiety, PTSD, and panic disorder. A family history of sleep paralysis is also associated with higher personal likelihood, suggesting a possible hereditary component. Some medications, including certain ADHD treatments, and substance use are also linked to increased risk.

Relationship to narcolepsy

Sleep paralysis is one of the four classic features of narcolepsy, alongside excessive daytime sleepiness, cataplexy (sudden muscle weakness triggered by strong emotion), and hypnagogic hallucinations. However, the large majority of people who experience sleep paralysis do not have narcolepsy — frequent episodes accompanied by daytime sleep attacks or emotion-triggered weakness are the signals that typically prompt evaluation for the condition specifically, rather than sleep paralysis alone.

Sleep paralysis and reported hauntings

The combination of waking paralysis and accompanying hallucination — commonly a sensed threatening presence, a felt weight on the chest, or a shadow figure in the room — closely mirrors many reported "bedroom ghost" and sensed-presence accounts documented elsewhere on The Vault. This same experience underlies Newfoundland's Old Hag folk tradition, and has been given similarly specific cultural names and explanations across many other traditions worldwide, long before its physiological mechanism was understood.

See also

• Hallucination
• Old Hag

External links

• American Academy of Sleep Medicine — Sleep Paralysis
• Sleep Foundation — Sleep Paralysis: Symptoms, Causes, and Treatment
• Cleveland Clinic — Sleep Paralysis