Sleeping and dreaming are some of the most fascinating aspects of psychology and neurology. We all do it, and yet many facets are still not widely understood by scientists. Weirder still are the fast array of parasomnias and other sleep conditions that many people experience in their lifetime.
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Here are just a few of the strangest sleep conditions we know about:
Lucid dreaming
Most people will experience this at some point in their lives; it essentially refers to the knowledge that one is dreaming while in a dream. Sometimes this means that one can actually manipulate events or images within their own dreams. People who lucid dream often find that closing one's eyes or "dying" in the dream can wake them.
False awakening
As self-explanatory as it gets, this literally means when you think you've woken up from a dream, only to find that you are still within the dream. An intensely horrifying experience if you're having a nightmare, and a frustrating one if all you're dreaming about is going to work.
Night terror
Often misconceived to be just really bad nightmares, night terrors are actually very different. Nightmares are essentially just bad dreams that take place during rapid eye movement (REM) sleep. Night terrors have nothing to do with dreams; they simply pertain to the feeling of dread that one can experience during stages 3-4 of non-rapid eye movement (NREM) sleep. It's most common in children ages three to 12-years-old.
Somnambulism
The scientific word for sleepwalking, this is one of the most common parasomnias. Contrary to popular belief, sleepwalkers do not dream while they are moving around. Sleepwalking takes place during stages 3-4 of the sleep cycle, known as slow wave sleep. The sleepwalker is not fully conscious, nor have they lost consciousness completely, and they may exhibit bizarre or dangerous behaviour, or else mutter incoherently.
Exploding head syndrome (EHS)
Also known as episodic cranial sensory shock, snapping of the brain and auditory sleep start, EHS is a condition in which a person experiences a loud noise sometimes accompanied by a flash of light while asleep. Sufferers tend to jerk awake and may immediately suspect that their house is being broken into, or that a car crash has occurred outside. While the cause is unknown, possible explanations include ear problems, psychological stress and seizures.
Hypnic jerk
The sensation of falling while in the early stages of sleep, where the sleeper awakens from their slumber with a start often having imagined themselves tripping over or falling off a ledge. Other names for the condition are hypnagogic jerk, sleep start and myoclonic jerk, because it involves an involuntary muscle movement known as myoclonus.
Sleep paralysis
It might surprise some people to know that everyone experiences "sleep paralysis" in a certain sense. The body enters a state of muscular weakness during REM sleep known as REM atonia to prevent the person from acting out their dreams. The only things that are able to move are the eyes.
Sometimes this state does not wear off immediately upon waking. Between 8% and 50% of people have experienced still being in that paralysed state while awake. While it is not harmful and only lasts a couple of minutes, it can be very terrifying; the person cannot move a muscle and will also have problems breathing. Many report a feeling of immense pressure on their chest.
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This sensation has given rise to a number of folk tales, and even the word "nightmare" refers to a mythical "mare" or demon that sits astride the chest during bad dreams and sleep paralysis, possibly derived from hallucinations that a sufferer may experience when they awaken.
REM sleep behaviour disorder
For reasons largely unknown to sleep experts, studies have shown that there are a few rare cases of people who do manage to act out their dreams. The sufferer's body has not fallen into an atonic state during this experience, and are thus capabale of both simple and complex motor function during REM sleep. This becomes concerning indeed when it involves a sleeping person violently attacking their partners. There have been cases of people murdering their spouses in their sleep because of this condition.
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