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Seven strange things that can happen when you sleep

Everyone loves a good kip, but for some of us it’s more complicated than turning off the lights and counting sheep. Around 25% of the UK population suffer from some form of sleep disorder, which can make night-time more than a little eventful…

As , we look at a few of the other familiar, lesser­β€known and often extraordinary-­sounding conditions that can occur when we close our eyes.

1. Sleep paralysis

As many as 1 in 20 people will experience vivid hallucinations while falling asleep or waking up, while also completely unable to move. Sleep paralysis happens during REM (rapid eye movement) sleep – the stage usually associated with vivid dreams. During REM sleep our muscles are paralysed (presumably to stop us acting out our dreams!) but with sleep paralysis something goes a little bit awry: the brain wakes up but the body doesn’t. Someone experiencing it can normally open their eyes and see their surroundings but they can’t move, and have dream imagery coming through into normal consciousness. The result can be terrifying: people describe a very powerful sense of fear, seeing supernatural beings or intruders in the room with them, and a sense of being crushed, often by a demon-­like figure sitting on their chest.

2. Exploding head syndrome

A related condition is the dramatically titled “Exploding Head Syndrome”, which typically occurs when the person is falling asleep or waking up. As they drift off to sleep they will perceive an abrupt and extremely loud noise. It’s very often an “explosion” but people also report hearing fireworks, screams, doors slamming and cymbals – all kinds of different, but equally startling, noises. Sometimes the noise is accompanied by a visual flash. The light or noise are only ever hallucinatory, but they wake the person up with a jolt, as if they were real.

3. Hypnagogic jerks

Ever been dozing off when you’ve suddenly had the sensation of falling off a cliff, and woken with a start? If the answer’s yes then you’ve probably experienced a hypnagogic jerk – also referred to as a hypnic jerk, sleep start, sleep twitch or night start – an involuntary flexing of the muscles that can wake us with a start and simultaneously give us the illusion that we’re falling. The causes of hypnagogic jerks are disputed but one theory points us towards our primate forebearers. Could it be an archaic instinct telling us that if we relax our muscles during sleep we’ll fall out of the tree?

4. Sleepwalking

This is when a person walks or carries out other activities while not fully awake. It usually occurs during a period of deep sleep, and although the cause of the phenomenon is unknown, it seems to run in families. It’s also more common in youngsters, with around 20% of children likely to sleepwalk at least once. Although sleepwalkers generally stick to simple, repeated behaviour – like sitting up in bed, opening cupboards or getting dressed – nocturnal ramblers have been known to drive, raid the fridge and even climb a crane!

5. Sleep talking

Some of us like to have a chat during the night – even if we’re asleep. Sleep talkers are typically unaware they’re doing it and what they say can range from coherent and complicated to mumbled gibberish. The phenomenon can often cause embarrassment, or irritation to a bed partner (if an ex-lover’s name comes up, for example). Worth remembering that the law accepts that anything said during sleep is not a product of a conscious or rational mind and won’t hold up in court!

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6. Recurring dreams

Dreaming is our subconscious brain re­β€evaluating and processing our experiences, before filing them away as memories. As such, recurring dreams can indicate the presence of an unresolved issue in a person’s life. If the recurring dreams stop, it may be that the conflict has been successfully resolved. A common recurring theme is being naked in an inappropriate situation. This could be because the subject is worried about being metaphorically “exposed” in a professional or social scenario.

7. Periodic Limb Movement Disorder

People with PLMD make repetitive movements, often in the lower limbs, at regular intervals – typically every 20 to 40 seconds. These twitches or jerky movements might be in episodes that last anywhere from a few minutes to several hours – though often a person doesn’t know they have it until their partner alerts them to the fact. The exact cause of PLMD remains unknown, although scientists believe that the nervous system is at play is some way. It’s not a serious condition but can often lead to extreme fatigue in the day due to chronically interrupted sleep.

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