Little Known Sleep Conditions

Many of us know that getting a good night's sleep is a really important part of living a healthy and happy life. However, sleep can be quite strange and interesting. In fact, there are many sleep conditions that you may not of heard of, but that affect many people across the world.


Somnambulism is another word for sleepwalking. Sleepwalking usually occurs when someone has been in very deep sleep (non-REM), rather than someone "acting out their dreams". The sleepwalker will partially wake up from deep sleep, open their eyes, and start walking around. However, they are not conscious and awake.They will typically make slow movements around the house, such as walking around the bedroom or even going downstairs and opening the fridge.

Sleepwalking itself isn't dangerous to the person experiencing it, but it can be a probem if they harm themselves by doing something in their sleep - such as falling down the stairs, or even climbing out of a window while asleep. If you or a loved one sleepwalk during the night, then it's important to put stair gates at the top and bottom of the stairs and to make sure that any windows are locked to avoid accidents during the night. If you find somebody sleepwalking in the night, then simply encourage and guide them back to their bed rather than waking them up.

What can you do to prevent sleepwalking? Sleepwalking is more likely to occur if you are stressed, sleep, deprived, or have drunk a lot of alcohol. It also tends to run in families and is more common in children, as people often outgrow sleepwalking in adulthood.

Lucid dreaming

Lucid dreams are dreams that you have when you are conscious that you are asleep, and you are able to direct and control parts of your dream. Around half of people report experiencing at least one lucid dream in their lives, while one study found that 14% of people reported regularly having lucid dreams.

Although it might sound fun to be able to control your dreams, there is limited evidence as to whether it's actually a good idea to deliberately try to have a lucid dream or not. For people experiencing post-traumatic stress disorder (PTSD), and repeated nightmares, lucid dreaming can help people take control of the scary dream and stop it from happening. However, techniques used to force lucid dreams affect sleep artcitecture and can often cause increased awakenings, potentially leading to sleep deprivation (with its negative health consequences).

Night terrors

Night terrors are completely different from nightmares. Nightmares are bad dreams with a scary plot and people often wake up from the nightmare upset remembering their bad dream. Night terrors are not dreams and they do not have a plot or storyline that the person experiencing them can explain. They occur from deep sleep (just like somnambulism) and happen when somebody partially wakes up from deep sleep, but is also still partially asleep.

When someone experiences a night terror, they will appear to wake up in bed and be screaming and seem inconsolably upset. However, they are not actually awake or truly upset. Night terrors are not dangerous, and the person experiencing them doesn't need to be woken up from them. Often people experiencing night terrors will not even remember that it happened the next morning – it's only those who are woken by the screaming who are affected by it.

Sleep paralysis

Sleep paralysis is a fascinating condition where people wake up from sleep, but feel that they are paralysed and unable to move. The experience is almost always accompanied by a crippling fear. The person experiencing it may experience the presence of someone else in the room, that is often described as a witch, the grim reaper, or even an alien!

Sleep paralysis occurs when someone is woken from REM sleep, but their body remains "asleep", and as such remains paralysed. When somebody is in REM sleep, the body is paralysed so that they don't act out their dreams. In sleep paralysis, the person can open their eyes and is conscious, but is completely unable to move their body, because their body still thinks that they are asleep. This can lead to panic and fear as the person feels paralysed and trapped, and is unable to crying out for help.

People who experience sleep paralysis can often be very distressed by the experience because it is so scary. As with many other sleep disorders, although distressing, it is not a problem in itself. Sleep paralysis is particularly common if someone also has narcolepsy.


Narcolepsy is a sleep disorder where people fall asleep without warning during the daytime. It is often accompanied by excessive daytime sleepiness.

When someone has narcolepsy they may feel weak or lose muscle control when emotional or laughing, and may find themselves falling asleep unexpectedly at inapproriate times, such as when driving a car. They will fall straight into REM sleep, which is unusual because most people without narcolepsy tend to not enter REM sleep until around 90 minutes after falling asleep.

Treatment for narcolepsy tends to involve stimulant medication to keep the person awake during the daytime.

White mannekin head with white smoke
Exploding head syndrome

This extremely scary sounding condition, is actually completely harmless. Exploding Head Syndrome (EHS) is when someone is sleeping, but is then awoken abruptly by a sensation of an explosion or loud pop inside their head. The loud noise and violent sensation are not accompanied by any pain, but the shock of waking up so abrupty can cause anxiety and stress, leading to ongoing sleep disuptions. People can become fearful of falling asleep because they don't want to be woken up by such a shocking experience again.

EHS is a rare disorder and treatment is usually education about what is really going on when this happens, and good sleep hygiene. Often, when someone understands that the EHS symptoms (such as the explosion sensation in their head) are not actually a medical problem, then they will be less stressed about them, and their symptoms may even disappear altogether.

Fatal familial insomnia

When someone has trouble falling asleep, then a quick Google of "insomnia" can often lead (worryingly) to the disorder, fatal familial insomnia (FFI). FFI, as the name suggests, is a sleep disorder where the sufferer develops such a severe insomnia that they cannot fall asleep, and they eventually die from this lack of sleep. Thankfully, however, this disorder is an exceptionally rare genetic degenerative brain disorder which only affects around 1 person per million.

Although FFI is fatal, and there is no current cure, it is so exceptionally rare that people shouldn't worry about it happening to them if they have a night or two of poor sleep.


DR LINDSAY BROWNING from TROUBLE SLEEPING is a sleep expert, Chartered Psychologist and neuroscientist. She is the Sleep Ambassador for And So To Bed. Dr Browning works with INDIVIDUALS and COMPANIES to educate about better sleep and to resolve sleep problems such as insomnia. You can follow her on TWITTERINSTAGRAM and FACEBOOK.

Posted by Dr Lindsay Browning
20th July 2023

Back to sleep talk