Few moments feel better than climbing into bed, letting the day’s stress fade and drifting towards a deep, restful sleep. Then, out of nowhere, you get the unmistakable sensation that you’re falling — and your body suddenly jolts you awake. It can be startling, disorientating and especially frustrating when all you want is an uninterrupted night’s sleep.
So what causes that sudden twitch just as you’re falling asleep? Dr Amir Khan, known for sharing medical advice on ITV’s Good Morning Britain and Lorraine, addressed the common sleep phenomenon in a TikTok video.
Dr Khan said: “Have you ever felt you’re falling just as you nod off? That sudden jolt awake is actually called a hypnic jerk.”
He explained that the experience is linked to the way the body relaxes at the start of sleep. “As you drift into sleep, your muscles relax, and sometimes your brain interprets that as falling. It’s a misinterpretation, so it sends a quick signal to your body to catch you, and that’s why you twitch awake.
“Now, some scientists think it’s an ancient survival reflex, back to when we slept in trees a sudden twitch might have stopped us from actually falling. It’s totally harmless. More common when you’re stressed, have caffeine late, or you’re just super tired.”
Reassuring viewers that hypnic jerks are “totally normal, totally harmless”, he added: “So next time it happens, don’t panic. It’s just your brain being quirky.”
What is a hypnic jerk?
A hypnic jerk, short for hypnagogic jerk, is an involuntary muscle spasm that occurs during the transition from wakefulness to sleep, according to The Sleep Foundation. The sleep health organisation says around 70 per cent of people will experience hypnic jerks at some stage in their lives.
The Sleep Foundation explains: “Also known as a sleep twitch, myoclonic jerk, or night start, it often feels like a jolt, a falling sensation, or a sudden kick from your own body. These movements usually affect one side of the body, like an arm or leg, and may be accompanied by a brief dream or startled feeling.”
The organisation added: “Researchers don’t know for certain what causes hypnic jerks, but there are some theories. Hypnic jerks and other types of myoclonus (involuntary muscle twitching) start in the same part of your brain that controls your startle response.
“When you fall asleep, it’s suspected that a misfire sometimes occurs between nerves in the reticular brainstem, creating a reaction that leads to a hypnic jerk. For example, it may be that when your muscles relax completely, even though this is a normal part of falling asleep, your brain mistakenly assumes you’re really falling and reacts by twitching your muscles. It may also be possible that hypnic jerks are a physical reaction to the dream-like imagery that accompanies them.”
The organisation added doing the following things may reduce hypnic jerks:
