A Sudden Jolt During a Nap! For Those Who Wake Up from a Falling Dream: That "Startle" Might Be a Misunderstanding by the Brain

1. Why Does the "Jerk" Happen Right Before Falling Asleep?

At night, after finally finishing today's tasks, you get into bed.
Just as your consciousness begins to drift away,
—Bang!

Your legs or arms jerk significantly, waking you up.
Many people have probably startled their partner sleeping next to them.

The official name for this phenomenon is the hypnic jerk.
In Japanese, it's also called "sleep onset myoclonus" or "sleep start." Globally, it's considered a very common phenomenon experienced by about 70% of people at some point in their lives.The Independent

What is characteristic is that it's not just a simple jerk; it's often accompanied by a **"falling dream" or "tripping sensation."** People often report waking up with their whole body tensed after dreaming of missing a step on the stairs or falling off a cliff.

2. A Minor Misfire Caused by the Brain's "Misunderstanding"

So, what exactly is happening inside the body?

Sleep researchers explain hypnic jerks as a **"small misunderstanding by the brain." When a person is falling asleep, the muscles gradually relax, and the body loses tension. This natural relaxation can sometimes be misinterpreted by the brain as "about to fall" or "about to trip."**The Independent

As a result, a command is rapidly sent to the muscles to "correct your posture!" causing the whole body or one side to jerk suddenly. This quick muscle contraction is the hypnic jerk.

Medically, such brief muscle twitches are called **myoclonus.** Hypnic jerks that occur at sleep onset are considered a type of myoclonus.Wikipedia

For most people, it's a painless, very brief event that lasts only a few seconds. However, it can be accompanied by a racing heart, momentary heavy breathing, or a "falling into an abyss" sensation, which can be quite unpleasant for some.

3. Is It a Sign of Illness? When to Worry and When Not to

In conclusion,hypnic jerks are harmless for most people, and no special treatment is needed.

The concern is how frequently they occur and whether they are accompanied by other symptoms.

When You Don't Need to Worry

• Occasional occurrences

• No pain and can quickly fall back asleep

• No impact on daily life

If it's at this level, it's generally considered to be "just the way the body is structured."The Independent

Cases to Be Cautious About

On the other hand, it's reassuring to consult a doctor in the following cases.

• It occurs almost every night, making it difficult to sleep

• Muscle spasms continue during the day

• Accompanied by other neurological symptoms such as tremors, awkward movements, or difficulty walking

Some studies suggest that hypnic jerks may appear as an early symptom of Parkinson's disease. However, in such cases, other more typical symptoms, such as slowed movement or acting out dreams known as "REM sleep behavior disorder," are often present, and there is little need to suspect a disease based solely on hypnic jerks.The Independent

4. Are Medications and Caffeine Related? Triggers Found by Science

Cases have been reported where not only lifestyle habits but also medications and stimulants influence hypnic jerks.

Association with Antidepressants (SSRIs)

Some case reports have recorded that people taking SSRI antidepressants (such as escitalopram, sertraline, fluoxetine) experienced frequent hypnic jerks. There are cases where symptoms improved after stopping or changing the medication, and it's noted as a side effect to be aware of.The Independent

However, this is a relatively rare side effect, and it's strictly forbidden to stop medication on your own. If you suspect it might be due to medication, be sure to consult the prescribing doctor.

Caffeine, Nicotine, and Other Stimulants

Substances with strong stimulating effects, such as energy drinks containing caffeine, nicotine, and even cocaine, are also suggested to increase the frequency of hypnic jerks.The Independent

If you keep drinking caffeinated lattes or energy drinks until just before bed, or chain-smoke late into the night, your nervous system remains overly excited when you go to bed, making the brain's "misfire" more likely.

5. Why Fatigue, Stress, and Sleep Deprivation Increase It

In sleep medicine, the following factors are cited as conditions that make hypnic jerks more likely to occur.The Independent

• Sleep deprivation and irregular sleep patterns

• Increased stress and anxiety

• Excessive intake of stimulants like caffeine and nicotine

• Intense exercise just before bed

When the brain is in an "over-tense" state due to lack of sleep or stress, it may not have the leeway to perceive muscle relaxation at sleep onset as "finally able to rest," and instead may judge "sudden loss of strength = danger."

Additionally, late-night gym visits or intense workouts just before bed stimulate the sympathetic nervous system, increasing heart rate and body temperature. Since the body is fully active at a time when it should be calming down, the nerves remain excited even in bed. As a result, there may be an increased sensitivity to small stimuli at sleep onset, leading to more hypnic jerks.

6. "Jerk" Experiences Going Viral on Social Media

Recently, hypnic jerks have become popular as a relatable topic on social media.

Platforms like X (formerly Twitter) and TikTok see daily shares of posts like these.

• "Just as I was about to fall asleep, my leg jerked out, and I kicked the bed rail with full force. Woke up to my own scream."

• "Almost dozed off during a meeting, and my whole body jerked. And the mic was on. Legendary embarrassment..."

• "Had a falling dream and bounced on the bed like I jumped. The cat next to me was totally freaked out."

(Note: The above are "relatable" reconstructions based on actual posts.)

Searching hashtags like "#hypnicjerk," "#寝落ちビクッ," or "#sleep twitch" reveals a variety of reactions, from cries like **"I thought my heart stopped" or "I thought a ghost touched me,"** to reflections like
"Had a hypnic jerk again today, so it's time to reconsider my sleep deprivation."

From the partner's perspective, there are posts like,

• "My wife suddenly jerks at the start of sleep, making me think it's an earthquake every time."

• "My boyfriend's hypnic jerks are so intense that I sometimes almost fall out of bed."

Such posts show that

one person's physical phenomenon can affect the sleep of the person sharing the same bed.

7. Five Self-Care Tips for Hypnic Jerks You Can Start Today

Even if it's said to be "harmless," if it happens too frequently, neither the person nor those around them can sleep soundly. So, here are some self-care tips you can start today to alleviate hypnic jerks.

1. Regulate Your Sleep Rhythm

Try to go to bed and wake up at the same time every day.
Just this simple routine can significantly stabilize your internal clock and improve sleep quality. Establishing a bedtime routine (brushing teeth → light stretching → reading) can also be effective.

2. Limit Caffeine to "Up to 6 Hours Before Bed"

There are surprisingly many drinks containing caffeine, such as coffee, tea, energy drinks, green tea, and cola.Decide to avoid caffeine after 6 hours before bed to help calm your nerves at sleep onset.

3. Stop Using Your Smartphone Before Bed to Reduce Light and Information Stimulation

Continuously scrolling through social media in bed keeps the brain in an awake mode due to blue light and information stimulation.
At least put down your smartphone 30 minutes before bed, dim the lights, and switch to relaxation time, which helps not only with hypnic jerks but also with overall sleep quality.

4. Engage in Moderate Exercise "by Evening"

Exercise itself is beneficial for sleep, but intense exercise right before bed is counterproductive. Try to finish jogging or gym training by evening, and incorporate "cool-down" activities like yoga, stretching, or deep breathing before bed.

5. Don't Worry Too Much About "It Might Happen Again"

When hypnic jerks persist, you might brace yourself thinking, "It might happen again," which itself can become a stressor that disrupts sleep.

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