What causes sleep paralysis?

Causes of Sleep Paralysis

Sleep paralysis is primarily caused by the persistence of REM sleep muscle atonia into wakefulness, representing a dissociated state where aspects of REM sleep intrude into the waking state. 1

Neurophysiological Mechanism

Sleep paralysis occurs when there is a mismatch between sleep states, specifically:

• The intrusion of alpha electroencephalogram activity into REM sleep followed by an arousal response
• Persistence of REM sleep muscle atonia into the waking state 1
• Disruption in the normal transition between sleep stages, particularly when entering or exiting REM sleep 2

During normal REM sleep, the body experiences natural muscle paralysis (atonia) to prevent acting out dreams. In sleep paralysis, this paralysis continues briefly after the person becomes conscious.

Risk Factors and Triggers

Several factors increase the likelihood of experiencing sleep paralysis:

Sleep-Related Factors

• Irregular sleep-wake schedules 1
• Sleep deprivation 1
• Jet lag 1
• Poor subjective sleep quality 3
• Objective sleep disruption 3
• Sleeping in the supine position (on back)

Medical and Psychiatric Conditions

• Narcolepsy (sleep paralysis is one of the typical symptoms) 4, 5
• Post-traumatic stress disorder (particularly high prevalence) 3
• Panic disorder 3
• Anxiety disorders 3
• Other sleep disorders 6

Other Contributing Factors

• Stress and trauma 3
• Substance use 3
• Genetic influences 3
• Physical illness 3

Clinical Presentation

Sleep paralysis typically presents with:

• Inability to move or speak upon waking or falling asleep 2
• Full preservation of consciousness during episodes 4
• Episodes that last seconds to a few minutes and resolve spontaneously
• Possible accompanying hallucinations (visual, auditory, tactile) 2
• Significant fear or distress during episodes 2

Differential Diagnosis

Sleep paralysis must be differentiated from:

• Seizures (which involve loss of consciousness) 4
• Atonic seizures 4
• Cataplexy (triggered by strong emotions, particularly positive ones) 4
• Other parasomnias 6

Management Approaches

For isolated sleep paralysis, treatment focuses on:

1. Sleep hygiene education:

   • Maintaining regular sleep-wake schedules
   • Ensuring adequate sleep duration
   • Avoiding sleeping in the supine position
   • Minimizing alcohol and caffeine consumption near bedtime 6

2. Cognitive-behavioral approaches:

   • Meditation-Relaxation (MR) therapy has shown promise in reducing both frequency and distress of sleep paralysis episodes 5
   • Cognitive restructuring for associated anxiety and fear 1

3. Treatment of underlying conditions:

   • Management of narcolepsy if present 4
   • Treatment of other sleep disorders like obstructive sleep apnea 6
   • Addressing psychiatric conditions such as anxiety or PTSD 3

No specific pharmacological treatment is generally required for isolated sleep paralysis episodes, as they are benign and self-limiting 1.

Special Considerations

• Cultural interpretations of sleep paralysis vary widely across different societies, with some attributing the experience to supernatural causes 7
• Recurrent episodes affect approximately 7.6% of the general population 1
• Episodes may be more distressing when accompanied by hallucinations 2

Understanding the physiological basis of sleep paralysis can help reduce fear and anxiety associated with these episodes, which are generally benign despite being frightening.