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Imagine this scenario: You wake up in the middle of the night and find that you can't move your arms and legs, nor can you let out even the smallest sound
This is what's known as sleep paralysis, which unfortunately affects a large group of people.
According to research, around 7.6% of the general population experience at least one episode of sleep paralysis during their lifetime. This comes from a systematic review of 35 studies involving more than 36,000 participants.
Many report other horrifying things that occur at the same time, such as seeing shadowy figures standing by the bed, feeling an ominous presence in the room, or sensing an intense weight pressing down on their chest.
Experiences like these have inspired supernatural explanations in many cultures. In Malaysia, they're often described as "kena tindih", while similar folklore exists across Europe, Japan, and the Middle East.
So, what is sleep paralysis anyway?
Sleep paralysis is a recognised sleep phenomenon that occurs when parts of your brain wake up before your body has fully exited a stage of sleep called rapid eye movement (REM) sleep
Throughout the night, your brain cycles through several stages of sleep. One of the most important is REM sleep, when most vivid dreaming takes place.
During REM sleep, your brain temporarily switches off most voluntary muscle movement. This normal process, known as REM atonia, prevents you from physically acting out your dreams.
Sleep paralysis occurs when consciousness returns slightly earlier than your body's muscle control. Your eyes may already be open and you're aware of your surroundings, but the temporary muscle inhibition from REM sleep is still active for a few seconds or, more rarely, several minutes.
Although the experience can feel alarming, the paralysis is temporary and resolves on its own as the brain completes the transition into waking up.
Researchers don't know exactly why some people experience sleep paralysis while others never do, but several factors consistently appear across scientific studies
These include:
- Irregular sleep schedules
- Lack of sleep
- Shift work
- Jet lag
- Psychological stress
- Anxiety disorders
- Sleep disorders
Many people first notice episodes during periods of prolonged stress, such as university exams, major work deadlines, or after several nights of poor-quality sleep.
These factors make REM sleep less stable, increasing the chance that REM-related muscle paralysis briefly overlaps with wakefulness.
One reason sleep paralysis feels so convincing is that it often includes vivid hallucinations
Scientists believe these occur because parts of the brain involved in dreaming remain active even after conscious awareness returns.
Essentially, elements of your REM dream continue overlapping with your waking perception.
Researchers generally classify these hallucinations into three main categories:
- Intruder hallucinations: Where you sense another person or presence nearby
- Incubus hallucinations: Involving chest pressure, difficulty breathing, or the feeling that something is sitting on you
- Vestibular-motor hallucinations: Where you feel like you're floating, flying, falling, or leaving your body
These sensations can feel extraordinarily real because your brain's emotional and sensory systems are still partly operating in "dream mode", even though you're awake enough to recognise your surroundings.
This mismatch between consciousness and dreaming is also why many people remember sleep paralysis far more vividly than an ordinary dream.
That's not all, the most frightening part of sleep paralysis is the sensation that you can't breathe properly
During REM sleep, breathing naturally becomes shallower and more irregular than during wakefulness. At the same time, many of the accessory muscles that normally help expand your chest are less active because of REM atonia. Your diaphragm, the primary muscle responsible for breathing, continues to function normally.
When you wake into this state, the reduced chest movement can create the powerful impression that your breathing is restricted. Your brain may then combine these unfamiliar physical sensations with lingering dream imagery, leading to the vivid feeling that someone or something is pressing down on your chest.
Although intensely uncomfortable, sleep paralysis itself does not stop you from breathing or deprive your body of oxygen.
The good news is: Most people don't need treatment but recurring episodes might need some medical attention
For most people, doctors recommend improving overall sleep health by:
- Maintaining a regular sleep schedule
- Getting enough sleep every night
- Managing stress where possible
- Treating any underlying sleep disorders
If sleep paralysis occurs for you alongside excessive daytime sleepiness, sudden muscle weakness triggered by emotions, or other unusual sleep symptoms, consult a doctor or specialist to keep everything in check.
