Lots of times as I'm going to sleep I suddenly jerk awake. And sometimes it
feels like I'm falling down so it's kind of scary. What's going on? – Molly*
This body movement is what doctors and scientists call a
(or hypnagogic) or
jerk. It's also known as a "sleep start," and it can literally
startle you out of falling asleep.
This type of feeling is normal, and it can happen before people enter the deeper
stages of sleep. Doctors and scientists aren't really sure why our bodies do this,
but they have a few theories.
One theory is that the brain misunderstands what's going on as our muscles relax
before sleep. It's normal for the muscles to relax, of course, but the brain gets
confused. For a minute, it thinks you're falling. In response, the brain causes your
muscles to tense as a way to "catch yourself" before falling down — and
that makes your body jerk.
These body jerks can wake you up with a start — but they're nothing to worry about.
Lots of people fall right back asleep afterward.