You’re fast asleep. All of a sudden, you’re awoken – and not by your alarm clock. It’s still dark, but you sense a disturbing presence in the room hovering near your bed, watching you. And you’re unable to move. The scientific explanation of what happened is called sleep paralysis.
Scientists and psychologists will tell you it’s a frightening but normal phenomenon that most people encounter at least once in their lifetime. It happens when you become conscious while your muscles remain in the ultrarelaxed state that prevents you from acting out your dreams, says Dr Ong Thun How, director of the Sleep Disorders Unit at Singapore General Hospital. “This paralysis usually lasts only a short time,” he says, “and does not require any treatment.”
But the hallucinations and sensation of breathlessness that frequently accompany these episodes are what torments people more than mere paralysis alone, according to researchers James Cheyne and Gordon Pennycook from the University of Waterloo in Canada. Their study, published in the journal Clinical Psychological Science, further found that people were most distressed after such an episode when they held supernatural beliefs, suggesting that understanding why it happens helps you feel less unnerved.
Keep calm and realise you’re not alone
Sleep paralysis is common enough that nearly every culture across the world has had some kind of paranormal explanation for it.
In medieval Europe, you might think that sex-hungry demons violated you, or that the mare – a damned woman – tried to suffocate you in the night. In China, where the earliest written account of “ghost oppression” was found, a fearsome spirit holds you down. In the US, a scary old lady comes for you. And in more recent times, studies find claims of alien abduction may actually be describing an episode of sleep paralysis. Modern estimates of the number of sleep paralysis sufferers fluctuate as widely as 5 to 65 per cent of the population. For Dr Kenny Pang, medical director of Asia Sleep Centre, that figure is around 6 to 7 per cent in Singapore.
In a 2011 paper published in the Sleep Medicine Review, authors Brian Sharpless and Jacques Barber combined 35 studies from a variety of cultures and groups, and concluded that approximately 8 per cent of people experience sleep paralysis, rising to around 28 per cent in groups that experience disrupted sleep pattern, and up to 34 per cent in those suffering from psychiatric disorders such as anxiety and depression.
Your move: Lower you chances of phantom asphyxiation by reducing stress, getting enough sleep and avoid sleeping supine, says Dr Pang, explaining that sleep apnoea may also trigger this panic-inducing bedtime attack.
Tell yourself it’s all in the mind
It may be easier to blame sleep paralysis on evil spirits because what’s actually happening in your brain is much harder to explain. The strange phenomenon is caused by an overlap of the rapid eye movement (REM) and waking stages of sleep, says Associate Professor Loh Ngai Kun, a senior consultant in the Department of Neurology at the National Neuroscience Institute.
As you sleep, your brain cycles in and out of REM, during which special neurotransmitters are released that paralyse almost all of your muscles. That’s called REM atonia, and it keeps you from running in your bed when you’re dreaming of being chased. In an episode of sleep paralysis, your conscious mind wakes up before REM is completely phased out, and for the next few moments, you get to watch the dream – usually a nightmare – played out as a vivid hallucination before your eyes.
On top of that, REM atonia also removes control of your breathing. Combine this with your body’s fear response to take in more oxygen in the face of a perceived danger, and the struggle for air creates a sensation of suffocation.
Your move: Blink away spooky hallucinations by telling yourself it’s not real. “Reassurance is important,” suggests Dr Pang, “and most people can resolve the situation on their own.” However, if you suffer from a heightened state of anxiety, seeking treatment will help reduce the incidence of sleep paralysis, says Dr Ong.
Worst case scenario: Call the sleep doctor
Many who have experienced sleep paralysis do so infrequently, perhaps only once in a lifetime. But there are some associated sleep disorders that can be debilitating.
For example, sleep paralysis is closely associated with narcolepsy, a neurological condition where a person falls asleep abruptly and uncontrollably in the day. “In this disorder,” Prof Loh explains, “there’s an early onset of REM, making sleep paralysis a common feature. Still, it’s not necessarily related to neurodegenerative diseases.”
Your move: Getting treatment for any underlying sleep disorder can reduce sleep paralysis attacks. A 2002 paper published in the journal Sleep provided strong evidence that disruption to your sleep cycle can increase risk of sleep paralysis. The researchers were able to deliberately elicit sleep paralysis attacks in volunteers by waking them up every time they entered REM sleep, and eventually this caused a sudden onset of REM where the participants bypassed all other sleep stages and went straight into REM sleep from waking.