If you’re unsure if you’ve ever experienced a hypnic jerk, then ask yourself this question.
Have you ever woken up with a sudden jolt just as you’ve started falling asleep? Or maybe it felt like you were falling?
It could be that it felt like you were having a huge muscle spasm. You may have even felt a small shock sensation, or a bouncing feeling.
Perhaps it was even your partner that was experiencing it, and this in itself startled you back to consciousness.
It could be then, but not necessarily, that you experienced a hypnic jerk. And if so, you are certainly not alone.
It is estimated that around 70% of people may experience hypnic jerks at some point. I know I definitely have.
The world of sleep can be confusing, and there is no exception when it comes to the hypnic jerk. Confusing because it is also sometimes called by one of the following names:
- Night starts
- Sleep starts
- Hypnagogic jerk – hypnagogic being a term used to describe the period of time when falling asleep or waking up.
- Myoclonus, or myoclonic jerk – technically this is the medical term to describe an involuntary muscle twitch.
So what is a hypnic jerk exactly?
A hypnic jerk is an involuntary twitching of a muscle, or muscles (the myoclonus as mentioned above). They usually occur just as you are falling asleep. This is referred to scientifically as the hypnagogic state of consciousness.
This is why they are sometimes call hypnagogic jerks – because you most commonly experience them when falling asleep.
Note that hypnic is also a shortened version of the word ‘hypnagogic’. So you can see why there are all these possible expressions to describe the same thing.
When you experience a hypnic jerk it often causes you to wake up suddenly. When you wake up you may feel like you are experiencing the sensation of falling or jolting.
Note that the muscle twitching you experience also occurs in other situations. For example hiccups are also muscle twitches.
That strange time of the night
It is during this phase of falling asleep that several unusual phenomenon may take place. For example we discussed in a previous article the various sleep paralysis experiences people have. Those often come with bizarre or frightening hallucinations, or even out-of-body experiences.
Luckily there is nothing to be worried about – hypnic jerks along with these other phenomenon are not dangerous. They may be unsettling or frightening, but you do not need to fear going to sleep just because they may happen to you.
What causes the hypnic jerk?
So now you know that the hypnic jerk is a twitching of the muscles. But what causes the muscles to twitch?
As is often the case with the complex world of sleep, scientists are still not 100% certain about this. However, they do believe that the following factors can all contribute to hypnic jerks happening:
- Heavy exercise late in the evening
- Sleeping in an uncomfortable position
- Being very tired or fatigued
In addition to these factors which can contribute to the likelihood of a hypnic jerk occurring, there are 2 theories:
1. The first theory is that they happen as a normal part of the nervous system relaxing and slowing down. For example your breathing slows down, temperature drops and your muscles relax. They are then thought to occur because of the muscle relaxation.
2. The second theory is that while relaxing as you fall asleep, your brain gets confused and thinks you are falling. So it sends signals to the arms and legs to move to an upright position, resulting in the jerking sensation.
I have read viewpoints that the brain gets so confused it thinks the body is dying or falling to its death, and so wakes you with a jolt. But I personally don’t have much faith in that more extreme conclusion!
Make sure it isn’t another sleep disorder
If you are experiencing what you think are hypnic jerks, then for some people it could be something more serious like Apnea.
If you have breathing difficulties when sleeping, or wake up with a gasp or croak it may be wise to consult a medical professional to rule out Apnea.
A doctor would also be able to rule out the possibility of epilepsy. A small number of people with epilepsy only experience seizures during the sleeping hours.
It’s also possible that you may have restless leg syndrome, or periodic limb movement disorder. Again these would be diagnosed by a medical professional or sleep expert.
And most rarely of all, is the possibility of exploding head syndrome. This sleep disorder is also harmless, and is characterized by a very loud noise in your head. It could sound like a bang or any other loud noise, and will wake you up suddenly.
For the majority of people though, the hypnic jerk is a common and harmless phenomenon.
How can you prevent a hypnic jerk?
The hypnic jerk is such a common occurrence, that it may not be possible to prevent it happening completely. However, you can take steps to address some of the factors thought to increase the likelihood:
- You can cut down on alcohol and caffeine, especially in the 3-4 hours before going to bed.
- Try not to do heavy exercise late in the evening or night.
- Ensure you are getting sufficient magnesium and calcium in your diet – this can help with muscle and nerve spasms.
- Make sure you have a comfortable mattress and bedding, and that you sleep in a comfortable position, even with a partner. Personally I’ve found that I often experience a hypnic jerk when I am cuddling my partner to fall asleep, but am not really in the most comfortable position.
- If you are someone that suffers from anxiety or stress, then this is another issue to address altogether. However, you may find some useful advice on the section relaxation exercises for sleep. This provides practical short-term exercises, but also some ideas for more long-term techniques to tackle stress and anxiety.
- Try not to allow yourself to get too tired or fatigued. Obviously this depends on your particular circumstances, as some people understandably have very busy and tiring lives. But it may be up to you to try to give more importance to how much sleep you get. Have a read of the section on attitude towards sleep for some ideas about this.
Avoid the vicious cycle of worrying that you will experience a hypnic jerk
Hypnic jerks can become cyclical if you start worrying about them. This is a very common thing that happens with sleeping difficulties.
For example people who have insomnia will often start worrying that they won’t be able to get to sleep. This worrying then becomes the thing that causes their insomnia, even if the original cause has long gone.
So in the same way, if you worry about hypnic jerks, then you may start to get less sleep and become more fatigued. Being fatigued is thought to contribute to the frequency of hypnic jerks, and so it is more likely you will experience them.
You now know that a hypnic jerk is not dangerous, and that many people experience them. So hopefully you can start to relax about them, and not go to bed thinking about them.
What do you think about hypnic jerks?
There is not much research published about the hypnic jerk, mainly because it is thought to be harmless. So I’m interested to know what your experience is. How often do you have them? What seems to make them worse or more frequent? What do you find helps to reduce them?
Please share your experiences in the comments box below and help out other readers with your ideas and theories.