Have you ever found yourself peacefully drifting off to sleep, only to be suddenly awoken by… nothing? You jerk suddenly with your heart pounding, only to look around and realize that there is literally nothing to be concerned about. This involuntary jerking is unpleasant to say the least. It’s called hypnic jerking, and it’s a relatively common phenomenon. If you have experienced hypnic jerks and want to learn more about them, check out the guide below.


What is a Hypnic Jerk?

Hypnic jerks go by a number of names – sleep twitch, sleep start, hypnagogic jerking, hypnic jerking – but they all mean essentially the same thing. The medical terminology is myoclonus or myoclonic jerk, although these terms are not often used outside of the medical community.  Basically, hypnic jerking refers to any act of involuntary twitching or jerking that takes place as you are drifting off to sleep.

Different people react in different ways. For some, it may be just a slight twitch of the head. For others, it could be flailing arms or legs, or even violent jerking accompanied by a shout or scream.

Many people report a sensation of falling in your sleep, and jerk suddenly to “catch” themselves. Twitches can occur in arms, legs, or even the entire body.

Hypnic jerks are very common – some estimates note that up to 70% of the population experiences them. But why do they happen?


What Causes Hypnic Jerks?

There are several theories as to what actually causes hypnic jerking – the most common of which involves neuroscience principles.

Basically, scientists believe that there are two main systems in your brain that are essentially at odds with each other as you begin to drift off to sleep. The reticular activating system is active when you are active, helping you feel alert and keeping you awake. The ventrolateral preoptic nucleus system is responsible for sleep, and is sometimes referred to as the “sleep switch”. As control of your body is handed off from one system to the other, the reticular activating system sometimes still has influence over body movement, and may cause involuntary jerking in order to stay in control.

In other words, when you drift off to sleep, there are two systems fighting for control of your body’s mode. The video below does a good job of explaining this concept.



Can You Prevent Sleep Jerks?

Hypnic jerking is not dangerous, but it certainly isn’t pleasant. While there is no “cure” for this phenomenon, there are a number of steps you can take to potentially limit the frequency and intensity of sleep jerks:

  • Avoiding caffeine, particularly in the afternoon
  • Avoiding exercise in the evening
  • Reducing stress
  • Getting more sleep

There have also been a few cases in which hypnic jerks were identified as being caused by particular medications. One clinical trial noted that an SSRI named escitalopram caused on woman’s hypnic jerking. But, these cases are few and far between.

Most people experience hypnic jerking from time to time. It’s nothing to worry about, but if it’s causing significant disruptions to your sleep it may be worthwhile to speak with your doctor about it. Before you do that, however, we recommend trying some of the above steps (particularly reducing afternoon caffeine intake) to see if that helps.

Austin Meadows

Austin Meadows is a freelance writer, CPAP user, and self-proclaimed sleep enthusiast from the Seattle area. When he's not writing or researching about sleep science, you can find him snowboarding, cooking or traveling the world. Contact him at [email protected]

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