What does it mean when you twitch in your sleep?

Mention "hypnagogic jerk" or "hypnic jerk" to someone who has never heard the phrase before, and they could be forgiven for thinking you'd discovered a new personal insult. But a hypnagogic jerk or a hypnic jerk is just a medical term to describe a sleep twitch — that strong, sudden jolt that you (or your partner?) might get from time to time as you are drifting off to sleep (via Healthline). 

In spite of its rather dreadful sounding name, sleep jerks or twitches aren't symptoms of some strange disease. In a report carried by Sleep Medicine, researchers have reported that these twitches, jolts, and jerks are common — they happen to both men and women, and up to between 60 to 70 percent of the population (via ScienceDirect). 

These jerks or twitches can happen without warning, or they can have external triggers like sound or light (via LiveScience). And while many of these involuntary movements may not be strong enough to wake us up, researchers also say that they could be one reason why some of us suffer from either insomnia or sleep disruption.

The reasons why you jerk or twitch while you're sleeping

Live Science says doctors aren't sure why sleep twitches happen, but they have a few ideas. One theory is that hypnic jerks or sleep twitches happen when nerves misfire as you transition from wakefulness to sleep. Another theory is that our brains think our body's relaxation is a sign we're about to fall, and responds accordingly and tries to wake us up. This theory could explain why twitches and jerks can come with a feeling that you're falling (or dreaming that you're falling). 

But even if doctors can't explain hypnic jerks, they think they know what the triggers might be. Stress, anxiety, exhaustion, caffeine, poor sleeping habits, as well as increased activity shortly before bedtime (like exercising at night) can also make sleep twitches happen more frequently (via Medical News Today).

Psychologist and sleep specialist Michelle Drenup says, "More often than not, hypnic jerks are completely normal and nothing to be concerned about. However, if the jerks themselves, or the anxiety you experience about having them, are significantly disrupting your sleep, you should talk to a sleep specialist about your concerns."