It comes when your guard is down and you least anticipate it, seizing as you lie in bed just about to drift off to the land of Zzz's - a full body jolt! Suddenly you're falling, air whistling, death coming, surely...
Except you're still in bed. And then you pass out.
That, my dear scared sleepers, is a hypnic (or hypnagogic) jerk. It occurs as you slip into unconsciousness, and it's bloody terrifying (I experienced one but two days ago). While there are suggested causes for sufferers of regular hypnagogic jerks- odd sleeping patterns, high caffeine intake, anxiety and stress etc- experts concede that occurrences are largely random.
Imagine waking up to find that you've wrecked your bedroom while fast asleep. Clothes everywhere, bedside table broken, night-light smashed... It would be pretty shocking, wouldn't it? Well imagine that instead of a wrecked bedroom, you wake up bleary-eyed to find a dead, mutilated loved one in front of you, and there's blood all over your hands. Unless you have a deep love of interior design, the second one's probably worse, right?
Homicidal somnambulism, or sleepwalking murder, has been written of (and used as a defence in murder trials) numerous times in modern history. The most recent case of this kind was in 2005, when Jules Lowe was acquitted of murdering his father because he was sleepwalking at the time of the incident.
While there's a school of thought which believes the phenomenon of coma dreams is near-impossible, they are often remembered by survivors, who are able to reflect on bizarre extended visions they experienced while unconscious.
If that's true then what if, while in a coma, the weird dream-like experience takes a turn for the worse, and becomes a nightmare? And now you're trapped in a coma for what could be months, years, potentially decades, with the worst visions imaginable playing out before your very eyes...
Sleep deprivation is absolute hell
Q: I increase weight, I increase inflammation, I increase the chances of depression, cancer and rage. I damage skin irreparably, I decrease life expectancy and increase the risk of heart disease and high blood pressure. You're more likely to get a stroke if you experience me regularly, your bones will become weaker and more likely to break, you'll be less able to respond under pressure or cope with stress, or be creative, and your memory will worsen increasingly the longer you know me. And I might kill you... Apart from an absolute arsehole, what am I?
A: Sleep deprivation!
So you're sharing your bed with a bloodsucker...
If you've had your mattress for more than a year, you could have bed bugs. You may not know it of course, because their saliva has anaesthetic properties which prevent their victims from feeling a bite, aaaaand they hide most of the time, only appearing when they sense the telltale carbon dioxide emissions from a slumbering human.
But trust us, they're probably there, and this is probably happening when you sleep -
Of course no list about creepy sleep-related facts would be complete without a mention of sleep paralysis.
Essentially the feeling of your mind waking up while your body is still asleep, this explanation only hints at the terror. Scary symptoms noted by sufferers of sleep paralysis include: difficulty breathing, hearing noises (including whispers), a sense of other presences in the room. Long term sufferers can experience visions, with many people claiming to have seen a chilling, bestial old woman (who has been dubbed "The Old Hag"). The visions of this crone will often involve her climbing atop the paralysed person before slowly choking them.
Chilling? As a two time sufferer myself, I can confirm it certainly is.
What if toxic spores, such as those from videogame The Last of Us, are closer and more real than you think? As in, what if you're lying on top of them while you sleep? If you're one of the many millions of people who wake up with red eyes, a scratchy throat or itchy skin, chances are you could be sleeping on a mattress harbouring an insidious growth. If you find black spots on the outside of your mattress be warned: this is probably the mouldy tip of a particularly dangerous iceberg, as the inside of your mattress is most likely festering with poisonous mould (which may or may not turn you into a zombie).
Precognition, or future sight, is the rumoured psychic ability to witness future events before they happen. And one of the most commonly reported ways people witness these future events is through prophetic dreams.
Skeptics are quick to dismiss supposed precognitive dreams as coincidence, but research has actually shown that the "theory of coincidence" is as subjective as the phenomena it tries to explain...
Have you ever experienced a precognitive dream?
We have no idea why we sleep
There are a number of theories and proposed explanations for the reason why humans need to sleep, but shockingly none has ever been universally agreed upon (or convincingly comprehensive). Considering we spend around 1/3 of our lives in this detached unconscious state, the idea that there is a question mark over why we do this is pretty creepy.
One school of thought proposes that our brain needs to do a cleanup at the end of each day to digest the new information we've taken on, and chuck out all the useless rubbish. But if that's true then why, years after I heard it, do I still have this running through my head? Please, brain binmen, do a better job...