Have you ever jerked in your sleep so suddenly that it woke you up? If you’re not sure, your partner might know. Or maybe they’re the ones who often jolt while drifting off to sleep, causing you to wake up and wonder what happened. The natural phenomenon, which can be described as an “involuntary twitch,” is called a hypnic jerk. You may have heard it referred to as a sleep twitch, a sleep start or a hypnagogic jerk. Symptoms include a sudden twitch or shudder, sweating, fast-paced breathing and a racing heartbeat.
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Experiencing a hypnic jerk can be frightening, but the state of alarm typically only lasts for a few seconds. If you know about hypnic jerks from experience, don’t worry — most people experience the phenomenon at least once or twice during their lifetime. If they regularly interfere with your sleep, there’s a little more cause for concern, as they can hinder sleep quality and lead to anxiety.
So what’s behind this sudden jolt that interrupts your journey to dreamland? Researchers aren’t exactly sure. Studies have shown there are various factors that can increase their frequency, including physical and emotional stress and excessive caffeine intake. Another possible cause is a misunderstanding in the brain. When you lie down to go to sleep, your muscles relax. Researchers say this may lead the brain to believe that your body is actually falling, which causes it to panic and send signals to the muscles, telling them to wake up. The result? A hypnic jerk that jolts you awake and sends you into a short-lived state of panic.
Other factors that may play a role include drug and alcohol use, stress and over exhaustion. Working out late in the day or close to bedtime may also make you more likely to experience the phenomenon. Most hypnic jerks are brief and strong, but not dangerous. In some cases, you may not wake up at all. Hypnic jerks may also occur along with a "visual sleep start," such as the sensation of bright light, or an "auditory sleep start," including a loud snapping noise inside your head. Hallucination or vivid dreaming may also occur at the same time, and sometimes people cry out in their sleep at the same time the hypnic jerk occurs.
If you suffer from hypnic jerks, relaxation techniques before bed might help. Read more about that here.