What Are Hypnic Jerks—and How Do You Prevent Them?

Hypnic jerks, also known as sleep starts, are brief muscle contractions that occur at sleep onset. They're usually harmless and a normal part of falling asleep. The exact cause of hypnic jerks is unknown, but potential triggers include caffeine, nicotine, sleep deprivation, sleep apnea, intense physical exercise, and emotional stress. Maintaining a consistent sleep schedule and managing stress levels may help reduce the frequency of hypnic jerks.

Have you ever woken abruptly with a jerk or falling sensation? There’s a name for that: hypnic jerks.

Hypnic jerks can be unpleasant and even a bit alarming. If you’re ever concerned about the severity or frequency of hypnic jerks, don’t hesitate to discuss it with your doctor.

But the good news is that they’re usually a harmless, normal part of falling asleep. Only in rare cases do hypnic jerks lead to bigger issues such as injury or insomnia.

We talked to a sleep physician to find out everything you need to know about hypnic jerks, including what causes them and how to prevent them.

What is a hypnic jerk?

“Hypnic jerks, also known as sleep starts, are brief muscle contractions that occur at sleep onset,” says Stephanie Stahl, MD, sleep medicine physician at Indiana University Health.

For up to 70% of people, hypnic jerks are a part of everyday life. These involuntary muscle contractions can happen to adults of all ages and health levels.

What does a hypnic jerk feel like?

Hypnic jerks vary in severity and frequency. You might feel a fast jerking motion, a series of involuntary twitches, or even a stomach-churching falling sensation.

Sometimes your hypnic jerks wake you up—and sometimes they wake your bed partner instead. Because some hypnic jerks are only minor twitches, you might not rouse enough to know you’re experiencing them.

Hypnic jerks can also be multisensory. Stahl says some people think they heard a loud bang or saw flashing lights. “Some people may have multiple jerks or even cry out,” she adds.

What causes hypnic jerks?

It’s difficult to pinpoint the exact cause of hypnic jerks. Experts are still uncertain how to explain or predict them. Stahl says disruptions to your sleep-to-wake transition might contribute.

Here are some potential causes of hypnic jerks:

  • Excessive caffeine or nicotine: These common stimulants interfere with sleep by boosting alertness. Feeling restless or twitchy because of excessive caffeine or nicotine might increase your chance of experiencing hypnic jerks.
  • Insufficient sleep: Research from 2009 found that hypnic jerks can be triggered by fatigue or sleep deprivation.
  • Sleep apnea: This condition causes you to briefly stop breathing. The pauses or sudden restarts of airflow might trigger hypnic jerks.
  • Intense physical exercise: Working out just before bedtime can lead to restlessness, potentially contributing to hypnic jerks.
  • Emotional stress: You might experience more hypnic jerks when stressed or anxious, according to Stahl. Research suggests high cortisol (commonly called the “stress hormone”) disrupts your body’s natural sleep-wake schedule.

Are hypnic jerks dangerous?

Hypnic jerks alone aren’t considered dangerous. However, a hypnic jerk can make you accidentally kick your bed partner or stub your toe on the footboard. Frequent hypnic jerks might also trigger stress or anxiety about falling asleep, leading to restlessness and insomnia.

True hypnic jerks occur only during the transition between waking and sleeping. Consult a medical professional if you start experiencing sudden involuntary muscle contractions (myoclonus) during the day. Myoclonus can sometimes indicate an underlying neurological condition or adverse reaction to a medication. (Learn the science behind yawning.)

How to stop hypnic jerks

Because hypnic jerks aren’t dangerous, there’s no medical reason to try to prevent them. And because the cause of hypnic jerks is still unknown, there’s no surefire prevention method.

That said, maintaining a consistent sleep schedule might reduce the frequency of these sleep starts, says Stahl. Here are some other tips to help prevent startling yourself awake while falling asleep:

  • Reduce caffeine intake. Since caffeine might contribute to hypnic jerks, try lowering the amount of coffee, tea, and chocolate you consume—especially in the late afternoons and evenings.
  • Stop nicotine use. Nicotine is a stimulant, so it might increase the likelihood of hypnic jerks.
  • Manage stress levels. “Work on stress reduction,” suggests Stahl. In addition to possibly preventing hypnic jerks, lower stress levels can improve your overall sleep quality.
  • Go to bed on time. A regular-sleep wake schedule is vital to a smooth transition to dreamland. “Obtain adequate sleep, which is at least seven hours for adults,” says Stahl.
  • Get help for anxiety. Research suggests emotional stress can increase your chance of experiencing hypnic jerks. Addressing your anxiety can help calm your mind and help you transition more smoothly between sleeping and waking.


What are the symptoms of hypnic jerks?

The symptoms of hypnic jerks include involuntary muscle twitches or clenching. Some hypnic jerks are also accompanied by a falling sensation, visualization of flashing lights, or auditory hallucination similar to a loud bang.

Is a hypnic jerk a disorder?

Hypnic jerks alone don’t indicate a medical disorder. They aren’t considered dangerous or alarming. In fact, about 70% of adults experience sleep starts.

Is a hypnic jerk anxiety?

Hypnic jerks might be exacerbated by anxiety, but experiencing a hypnic jerk doesn’t necessarily mean you have anxiety. “Anxiety and stress are potential causes of hypnic jerks,” explains Stahl.

Sleep talking is another phenomenon that’s fairly common. Learn more about what causes sleep talking and how to stop doing it.

Was This Article Helpful?
Yes No

Related Stories