I’ve had that experience too and it really is startling. Sometimes I’ve had to sit up and catch my breath before I could begin to relax again after feeling like I was falling into the depths of a bottomless canyon. I wanted to learn more about this phenomenon and did a little research on the subject.
To answer your first question, yes, twitching just as you’re drifting off to sleep is a common occurrence and perfectly normal. It’s called hypnagogic jerks, hypnic jerks, or sleep starts and occurs during that period of time when you are transitioning from wakefulness to sleeping. Sleep experts tell us that up to 70 percent of people experience this sensation.
Sleep starts involve the whole body. It begins as a cramp in the neck and the rest of the body’s nerves react with a twitch or a shudder. They happen in just an instant, lasting only about half a second. Sometimes we are not aware of the movement, but other times it jolts us wide awake. It is sometimes accompanied by a sensation of falling. A rarer phenomenon that may occur along with hypnic jerks is a sensation of flashing lights or an even smaller number of people experience what is known as exploding head syndrome. That’s when the sleep start comes complete with the sound of crashing cymbals, a bomb exploding, or thunder bursting in your head.
Scientists aren’t quite sure what actually causes sleep starts. One group theorizes that hypnic jerks are just a normal part of the process of falling asleep. Still others with a more evolutionary attitude believe it’s a leftover ancient primal reaction, a reflex that occurred when the brain mistook muscle relaxation as a fall out of the tree where the primate was napping.
Although there are theories that these happenings are stimulated by stress, too much caffeine, anxiety, or sleep deprivation, there is no evidence to confirm that.
Most people aren’t bothered much by sleep starts and now that you know it’s perfectly normal I hope you can get a good night’s sleep. Sweet dreams.