Ever felt like you’re falling as you nod off? Here’s the lowdown on those weird things that can happen once you’ve closed your eyes
Nobody knows exactly why some people sleepwalk – which isn’t just walking, but can be anything from sitting up in bed to eating and even (in extreme cases) driving.
About 20% of kids do it at least once, but we usually grow out if it by puberty. There’s often a family link and it’s also associated with stress, alcohol, some medications (like sedatives), waking up suddenly from a deep sleep, or not getting enough sleep in the first place.
Sleepwalking is most likely to happen shortly after nodding off, when you are fast sleep.
Generally the odd sleepwalking episode isn’t anything to worry about. Ensure the sleepwalker is safe – remove tripping hazards, and keep doors and windows locked (you may want to hide the car keys too). Following general good sleep hygiene can also help.
2. Dreaming the same dream
You know – the one in which you’re at work with no clothes on. (What – you too?) Most of us experience recurring dreams – and there are some very common themes, like falling, your teeth falling out and flying.
Different psychologists, like Freud and Jung, had their own theories about the meaning of recurring dreams. However, it’s now generally accepted that each dream is personal to the dreamer. Dreamt you were back at school? Think about what school meant to you when you’re trying to interpret the dream – was it a happy or anxious time, for example?
Ultimately, there is no way of knowing for sure what a dream means – but if the interpretation matches something that’s bothering you, you can probably learn something helpful about yourself. 
3. Exploding head syndrome
It’s not, fortunately, quite as scary as it sounds. Exploding head syndrome, or EHS, is actually when a person imagines they hear a loud noise, like a bomb or gunshot, while falling asleep or waking up. A type of sleep disorder, this auditory hallucination isn’t painful or harmful – though for some people, it can be so loud or intense, it feels like it is. 
No one knows yet what causes EHS, though experts think it’s linked to being very tired or stressed. One theory is that it’s due to the brain shutting down in the wrong order while preparing for sleep. Normally the brain shuts down in stages but with EHS it may shut down all at once, causing the auditory hallucination.
There is no cure yet for EHS but just knowing about it and what to expect may help.
4. Sleep paralysis
Ever woken up and had a moment of panic because you can’t move or talk?
This feeling is caused by sleep paralysis, and while it’s only temporary, it can be pretty scary at the time.
Why does it happen? Each sleep cycle is split into REM and non-REM phases. Dreaming generally happens during REM sleep when our muscles (except our eyes and diaphragms) are paralysed to stop us trying to act out our dreams, with potentially painful consequences.
Sleep paralysis is when that normal temporary paralysis continues once we’ve woken up and are fully conscious again. It can last seconds or minutes.
Sleep paralysis is more common in teenagers, people who don’t get enough sleep, or sleep in an irregular way (for example, shift workers). Getting enough exercise can help.
5. Restless legs syndrome
This condition, which gets worse at night-time, is officially known as Willis-Ekbom disease.
Restless legs syndrome is a pretty common condition of the nervous system that makes people feel an irresistible urge to move their legs. In severe sufferers, it can cause insomnia and depression.
One in 10 of us will get it at some point, and it’s more common for women. It’s also a problem in pregnancy.
Experts think restless legs syndrome may be linked to how the body handles a chemical called dopamine, which has a role in controlling our muscles. Secondary restless legs syndrome is caused by an underlying health condition, such as iron deficiency or kidney problems.
Good sleep hygiene, treating the underlying health condition (with iron supplements for example) or in extreme cases monitoring the body’s dopamine, are all treatments for restless legs.
6. Feeling like you’re falling
Most of us are familiar with the feeling of being jolted awake, just as we were finally getting to sleep. It’s down to a sudden, involuntary muscle twitch called a hypnic jerk. It can happen in any part of the body and around 70% of us get them.
Most experts agree that hypnic jerks are caused when the muscles begin to relax just as you fall asleep. The brain senses the relaxation signals and misinterprets one as falling down. The brain sends signals to your muscles to keep you balanced – and that’s the hypnic jerk.
Hypnic jerks can occur more often if you’re anxious, tired, uncomfortable or have exercised too much.
7. Sleep apnoea
You might not even know if you have obstructive sleep apnoea (OSA). The signs include loud snoring, noisy breathing and regular periods when your breathing is interrupted by gasping or snorting.
It’s caused by the muscles and soft tissues in the throat relaxing enough to cause an airway blockage for longer than 10 seconds. It can be quite scary to hear. After a few seconds, the lack of oxygen triggers your brain to pull out of deep sleep and your airway reopens.
As you won’t remember that your sleep was interrupted, OSA often goes undiagnosed – unless someone else, like a partner or family member, spots it.
OSA is more common if you are overweight, male, over 40, and/or have a large neck. Lifestyle treatments, such as losing weight, can help, and you should see your GP for other treatments.