Surely it has happened to you at some point: you are about to fall asleep, your body begins to relax, your mind enters that state between wakefulness and sleep… And suddenly, you feel like you’re falling into the void, as if you’re stumbling in a dream. We take a small involuntary jump, wake up startled, and sometimes even get scared without knowing why.
This phenomenon is as common as it is perplexing, but science has a clear and fascinating explanation.
🧠 What is that feeling of sudden drop?
This is a phenomenon called “hypnic shaking” or “myoclonic spasm of sleep”. It is an involuntary muscle movement that occurs just when we begin to fall asleep, in the stage called the hypnagogic phase, that moment of transition between wakefulness and light sleep.
This spasm may be accompanied by a feeling of falling, a brief sleep, or a physical startle.
🤔 Why does it happen?
Although there is no single definitive explanation, researchers have proposed several theories that help to understand this phenomenon:
- The brain misinterprets the body’s relaxation
When the body relaxes quickly as you enter sleep, the brain can misinterpret this relaxation as a loss of balance or a fall, and responds by activating an impulse to “protect” you. It’s a similar reaction to when you lose your balance while awake. - Residues of neuromuscular activity
During the transition to sleep, motor neurons don’t shut down evenly. This desynchronization can produce involuntary spasms or muscle jerks, especially if there was stress or physical fatigue during the day. - An evolutionary inheritance
Some scientists believe that this response is a primitive reflex inherited from our ancestors. When they slept in trees, a muscle spasm when they went into deep sleep could have prevented falls by activating the muscles just in time. Although we no longer sleep on branches, our nervous system still has that reaction.
🔁 Is it something dangerous?
For the vast majority of people, you have nothing to worry about. It is completely normal and does not indicate any neurological problems. However, if these jerks become very frequent, intense or prevent you from falling asleep, it may be helpful to consult a professional.
🧘 ♀️ How to reduce that feeling?
While it can’t always be avoided, you can decrease the frequency of hypnic jerks with these habits:
Avoid stress before bed (reading, meditating, or breathing can help).
I cut back on caffeine and other stimulants in the afternoon.
Maintain a regular sleep schedule.
Avoid excessive use of screens before bedtime.
I slept in a comfortable and quiet environment.
💤 In short
That sudden feeling that you are falling just before sleep is a natural, harmless and very common phenomenon. Although it may scare you for a second, there is no cause for alarm. It’s just the brain adjusting to sleep… with a small startle included.