Hypnic Jerk: Why You Twitch When You Sleep

Why Do People Twitch in Their Sleep?

People twitch in their sleep for several reasons, many of which are completely normal. As the body transitions from wakefulness to sleep, the nervous system may misfire slightly, leading to sudden, involuntary muscle movements. These twitches can also be influenced by stress, anxiety, caffeine, or physical exhaustion, all of which can make the brain more reactive during the shift into sleep.

In some cases, twitching may be related to specific sleep disorders or neurological conditions, but for most people, occasional sleep twitches are just a harmless part of the sleep process.

What Is a Hypnic Jerk?

A hypnic jerk (short for hypnagogic jerk) is a sudden, involuntary muscle twitch that happens as you’re transitioning from wakefulness to sleep. 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.

What Do Hypnic Jerks Feel Like?

Hypnic jerks are a type of myoclonus Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , which is a category of rapid, involuntary muscle contractions, such as jerking or twitching. For the most part, hypnic jerks are painless, although some people do report a tingling or painful sensation. Most people report:

• Experiencing a single jerk, or multiple in succession
• Feeling like they’re falling
• Seeing flashing or blinding lights Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source
• Hearing banging, crackling, or snapping sounds
• Other sensations or mental imagery, such as a dream or hallucination

Hypnic jerks can feel different at various times. They can be strong enough to jolt a person awake and disrupt the process of falling asleep. Other times, they may be so mild that the affected person does not notice them at all—although their sleep partner might.

Hypnic jerks occur at any age, but are more common among adults. In part, this may be due to the fact that some of their potential causes, such as caffeine consumption and elevated stress levels, are also more common in adulthood.

Other Causes of Twitching While Sleeping

Not all nighttime twitching is a hypnic jerk. Several other health conditions can cause involuntary movements during sleep or while falling asleep:

Restless Leg Syndrome (RLS)

Restless leg syndrome causes uncomfortable sensations in the legs, often described as tingling, crawling, or itching. It leads to an irresistible urge to move the legs, especially at night, and can interfere with falling asleep.

Periodic Limb Movements of Sleep (PLMS)

PLMS involves repetitive, rhythmic movements—usually in the lower limbs—that occur during sleep, often without the person being aware. These movements can disrupt sleep and are sometimes linked with RLS.

Sleep Myoclonus

This refers to brief, sudden muscle jerks that can occur during sleep or while falling asleep. Unlike hypnic jerks, sleep myoclonus may be more frequent and can affect different parts of the body.

Fasciculation

Fasciculations are small, involuntary muscle twitches that occur just under the skin. They’re usually harmless and may happen while awake or asleep, often in the arms, legs, or eyelids.

What Causes Hypnic Jerks?

Researchers don’t know for certain what causes hypnic jerks, but there are some theories. Hypnic jerks and other types of myoclonus 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.

Certain risk factors may increase your likelihood of experiencing a hypnic jerk, including:

Stimulants Like Caffeine and Nicotine

Stimulants like caffeine and nicotine wake up your brain. These substances can also stay in your system for several hours, disrupting sleep. In one study, people who stopped drinking coffee six hours before bed Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source still had trouble falling asleep.

Vigorous Exercise at Night

In general, exercise is almost always beneficial when it comes to sleep. Regular exercise has been consistently demonstrated to improve sleep quality Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . However, exercise is an energizing activity that makes you feel more alert, rather than tired. For that reason, exercising too vigorously late in the evening may lead to hypnic jerks.

Sleep Deprivation

Trouble sleeping and lack of regular sleep overall, whether due to chronic insomnia, other sleep disorders, or simply a poor night’s sleep, can lead to sleep deprivation. Among other unwanted side effects, like poor mood and focus, sleep deprivation may increase your risk of hypnic jerks.

Stress and Anxiety

Both everyday stress Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source and diagnosed anxiety disorders Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source can contribute to insomnia, which leads to the kind of sleep deprivation that increases your risk of hypnic jerks. When you’re stressed or anxious, your cortisol levels remain elevated during sleep, which makes sleep less restful.

Anxious thoughts can also keep you up at night, making it hard for you to relax into sleep and disrupting the transition between wakefulness and sleep, potentially triggering a hypnic jerk. Some people who experience hypnic jerks frequently may even develop anxiety around sleep itself, which only increases their likelihood of experiencing sleep deprivation and more hypnic jerks.

Are Hypnic Jerks Normal?

Hypnic jerks can feel startling, but they’re completely normal and generally harmless. In fact, research suggests that up to 70% of people experience them at some point. While these sudden twitches might occasionally disrupt your sleep—or startle a bed partner—they don’t pose any real danger.

In rare cases, a particularly strong jerk might cause a minor bump or muscle spasm or cramp (like a charley horse), but serious injuries are extremely uncommon. For most people, hypnic jerks are just an occasional annoyance rather than a sign of any underlying health issue.

Babies Twitching in Their Sleep

It’s common for babies to twitch or move while they sleep, and in most cases, it’s nothing to worry about. These movements are usually a normal part of their brain and nervous system development. Sleep-related twitching can happen during light sleep and may include sudden jerks of the arms, legs, or face.

If the twitching seems excessive, continues when the baby is awake, or is accompanied by other unusual symptoms, it’s a good idea to check in with a pediatrician.

When to See a Doctor

If you only experience hypnic jerks, you probably don’t need to see a doctor. However, some symptoms similar to hypnic jerks may require medical attention. If, during the daytime, you experience multiple, persistent contractions in your muscles that spread to other parts of your body, you could be experiencing a different type of myoclonus, rather than a hypnic jerk. These types of myoclonus can be indicators of other medical conditions. 

If you experience other types of jerking movements during sleep beyond hypnic jerks as you fall asleep, they could be symptoms of periodic limb movement disorder. If you’re concerned your muscle jerks are a symptom of another issue, speak to your doctor.

How to Stop Hypnic Jerks

Hypnic jerks are a normal, albeit unpredictable, part of the experience of falling asleep. It’s unlikely that you’ll be able to completely eradicate them from your life, but you can reduce their frequency and intensity, and improve your sleep at the same time, with a few simple techniques.

Be aware that even after implementing these tips, you may still experience hypnic jerks on occasion. They’re considered a normal part of falling asleep. If you experience other movements that are disrupting your sleep, however, consult your doctor.

Adopt Better Sleep Habits

Improving your sleep hygiene can make it easier for you to sleep better more consistently, which may reduce the occurrence of hypnic jerks. Common practices include:

• Going to bed and waking up at the same time every day, even on weekends
• Setting your bedroom temperature to around 65 to 68 degrees Fahrenheit
• Making your bedroom as dark and quiet as possible, using blackout curtains or a white noise machine if needed
• Stopping the use of electronics at least one hour before bed
• Following a nightly bedtime routine

Reduce Your Stress

Reducing stress could lead to a reduction in hypnic jerks. Explore relaxation techniques like meditation, deep breathing, and yoga. Fill your bedtime routine with calming activities, like a warm bath or reading a book. If your stress and thoughts interfere with your quality of life, speak to a doctor or therapist.

Exercise Daily

Exercise daily to enjoy more restful sleep. Regular exercise can also help relieve stress Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . If you prefer a vigorous workout Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , schedule your exercise for earlier in the day to prevent sleep disruptions. If you can only exercise at night, opt for low- or moderate-intensity exercises like walking or yoga. Aim to finish your workout at least 90 minutes before bed to allow your heart rate to slow back down and prevent the occurrence of hypnic jerks.

Minimize Your Caffeine Consumption

Caffeine can provide some beneficial energy-boosting effects during the daytime, but consuming too much, especially later in the day, can interfere with your ability to sleep soundly. If you’re experiencing hypnic jerks and having trouble sleeping as a result, caffeine could be the culprit. Avoid consuming more than 400 milligrams per day, and schedule your last cup of coffee for at least eight hours before bedtime.

Avoid Nicotine and Alcohol

Nicotine is a stimulant that can impair your brain’s ability to wind down at night. It can also impact your sleep quality once you’re asleep. Although alcohol is a sedative, it can also disrupt your sleep architecture Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , leading to the sleep deprivation that increases your risk for hypnic jerks.

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