Is your house haunted? The science behind sleep paralysis

What is sleep paralysis?

Sleep paralysis is a relatively common sleep phenomenon that can make you feel as though you’re awake but unable to move. Some people also experience vivid hallucinations, which can make the experience feel incredibly real.

Sleep paralysis happens when you become aware of your surroundings while your body is still temporarily unable to move as it normally would during sleep. During rapid eye movement (REM) sleep, the stage when most vivid dreaming occurs, your brain temporarily switches off most of the signals that control voluntary muscle movement. This is a normal protective mechanism that stops you from physically acting out your dreams.

Usually, this temporary muscle paralysis ends before you become fully awake. However, during sleep paralysis, your awareness returns before your muscles regain their normal movement.

You may feel conscious and able to see your bedroom, but find that you cannot move your arms or legs, sit up, or speak. You can usually still breathe, although your breathing may feel uncomfortable or restricted. An episode can last from a few seconds to several minutes. Although it can be extremely frightening, sleep paralysis is generally harmless.

Why do people see ghosts during sleep paralysis?

One of the most unsettling aspects of sleep paralysis is the possibility of hallucinations. These can occur as your brain moves between dreaming and wakefulness, allowing dream-like experiences to overlap with your perception of the real world.

People report a range of experiences, including:

• Sensing a presence - feeling that someone or something is in the room, even when nobody is there.

• Seeing figures or shadows - noticing a person, dark silhouette, or frightening creature nearby.

• Feeling touched or restrained - experiencing the sensation that something is holding you down, sitting on your chest, or pulling at your body.

• Hearing strange sounds - hearing footsteps, whispers, voices, or other noises that seem to come from the room.

These experiences can be exceptionally vivid. You might recognise your bedroom and believe you are fully awake, making it difficult to distinguish a hallucination from something happening around you. The sensation of a threatening presence is particularly well documented. Sleep researchers sometimes describe this as an intruder-type hallucination. Other people experience sensations of floating, flying, or leaving their body.

Although these experiences may seem mysterious, they can be explained by the unusual overlap between dreaming, awareness, and temporary muscle paralysis.

What causes sleep paralysis?

Sleep paralysis occurs when the normal transitions between sleep and wakefulness do not happen quite as expected. It is not always possible to identify a single cause, but several factors are associated with an increased likelihood of experiencing it.

These include:

• Sleep deprivation - not getting enough sleep can disrupt normal sleep patterns.

• Irregular sleep schedules - shift work, jet lag, or frequently changing your bedtime can affect your sleep-wake cycle.

• Stress and anxiety - periods of increased stress may be associated with more frequent episodes.

• Sleeping on your back - sleep paralysis appears to occur more often when people sleep in this position.

• Certain sleep disorders - sleep paralysis can be associated with conditions such as narcolepsy, which affects the brain’s ability to regulate sleep and wakefulness.

Sleep paralysis can happen to anyone, although it is often first experienced during adolescence and may recur during adulthood. Having an episode does not necessarily mean that you have an underlying sleep disorder.

How can you stop sleep paralysis?

There is no guaranteed way to prevent sleep paralysis, but improving your sleep habits may reduce the likelihood of further episodes.

You can try to:

• Get enough sleep - most adults need around seven to nine hours each night.

• Keep a regular routine - try to go to bed and wake up at similar times every day.

• Create a relaxing bedtime routine - allow yourself time to wind down before bed and try relaxation techniques if stress is affecting your sleep.

• Make your bedroom comfortable - keep it dark, quiet and at a comfortable temperature.

• Consider your sleeping position - if episodes happen frequently while sleeping on your back, try sleeping on your side.

• Limit caffeine late in the day - caffeine can interfere with your ability to fall asleep and stay asleep.

If you experience an episode, remind yourself that it will pass. Try to concentrate on slow, steady breathing rather than fighting to move your whole body. Some people find it helpful to focus on moving a small muscle, such as a finger or toe, although this is not a guaranteed way to end an episode. Sleep paralysis usually resolves on its own, without treatment.

When should you see a doctor?

Occasional sleep paralysis is not usually a cause for concern. However, speak to your doctor if it happens regularly, makes you afraid to go to sleep, or leaves you excessively tired during the day. It is particularly important to seek medical advice if you also experience:

• Significant daytime sleepiness despite getting enough sleep.

• Sudden episodes of muscle weakness triggered by emotions, such as laughter or surprise.

• Other persistent or unusual sleep-related symptoms.

These symptoms may indicate an underlying sleep disorder, such as narcolepsy, which may need further assessment. Hallucinations can also occur for reasons other than sleep paralysis. If you experience them when fully awake - particularly if they are new, persistent, or accompanied by other symptoms - speak to a healthcare professional.

Seek urgent medical help for sudden confusion or hallucinations accompanied by severe illness or other acute neurological symptoms.