So you're finally drifting off to sleep when suddenly YOU'RE FALLING...but not really. Tap to play or pause GIF Tap to play or pause GIF Cartoon Network / Via bustle.com You feel like you're sinking and your entire body jerks to wake you up in a panic. WTF was that?! Chances are, you've experienced this a time or two. It's super weird and super common, but what's actually going on, and why does it happen? We spoke to sleep doctor Michael Breus, PhD, clinical psychologist and fellow of the American Academy of Sleep Medicine, to find out. It's actually called a "hypnic jerk" or "sleep start," and there are a few theories to explain this bizarre phenomenon. Adriano Agulló CC / Via Flickr: lost__in__spain Hypnic jerks are a natural part of the sleep process, so many doctors believe it's just the body "twitching" as it slowly shuts down for rest. Another leading theory, Breus says, is that it happens when the body goes through the first sleep stage too quickly, because it's so exhausted. During the first stage of sleep, which usually only lasts a few minutes, your breathing and heart rate slows down and your sleep is still very light. If the body speeds through this stage and "shuts down" too fast, it might trigger the brain to think your vitals are actually failing and in response, it jerks the body awake. "It might be a kind of protective mechanism, but we really aren't sure because it's difficult to study," Breus says. Those visuals of falling or tripping? Scientists aren't really sure why those happen either. Tap to play or pause GIF Tap to play or pause GIF Disney / Via gif-database.tumblr.com This jolting up is usually accompanied by dreams of falling, tripping, maybe even leaning too far back in your office chair. You get the sensation that you're losing your balance and you jerk awake. "We don't have a great answer to the visual component, but we think it might be the easiest way for the brain to interpret the rush or feeling of falling into sleep too quickly, like a lack of balance if you faint while standing up," says Breus. Otherwise, these visual dreams are pretty subjective and individual, so it's difficult to study. But we do know that hypnic jerks happen as a result of sleep deprivation, stress, or intoxication. Nickelodeon / Via spongegifs.tumblr.com / gifemotions.tumblr.com Doctors believe that hypnic jerks happen when you deprive yourself of the quantity or quality of sleep. So that could mean falling way short of the recommended 7–9 hours of sleep per night. Or it might mean your quality of sleep is being affected by things like stress, caffeine, or sleep disorders like sleep apnea or insomnia. "Alcohol is another huge factor — many people get hypnic jerks after a night of drinking," says Breus. Hypnic jerks aren't really a symptom of a sleep disorder — though they may be a sign that you aren't sleeping well. Otherwise, they're just random, and it's no big deal if you get them every once in a while. It's not the same as when you drift off while sitting up and your head bobs up suddenly. Tap to play or pause GIF Tap to play or pause GIF Polygram Filmed Entertainment / Via gifemotions.tumblr.com This might feel like a hypnic jerk, but it's actually a different kind of protective mechanism which evolved in humans once we started walking upright. "Your head weighs roughly 8 pounds so if it falls over too far, it will bend your air pipe in a way that makes it difficult to breathe. The brain jerks your head back up to to straighten the air pipe back out so you can breathe properly," says Breus. So this head nod is basically your body's way of looking out for you when it's 4 p.m. on a Monday and you're quite literally nodding off in your desk chair. Hypnic jerks are super common and they won't harm you — but they can contribute to sleep loss. Creatas Images / Getty Images / Via thinkstockphotos.com According to the National Sleep Foundation, about 60%–70% of the population experiences hypnic jerks. Most of the time, they're totally harmless. "There are no serious consequences, it won't give you a heart attack or anything — the worst that could happen is you jerk so hard that you fall out of bed," says Breus. But if hypnic jerks become frequent and intense, they may keep you awake or lead to a fear of falling asleep, which results in chronic insomnia. So it's important that you do keep track of them if they start to interfere with your sleep and energy levels. And they might even be more annoying to your partner, since hypnic jerks can happen without you knowing. IPG Gutenberg UK Ltd / Getty Images / Via thinkstockphotos.com "I've had patients whose hypnic jerks are so frequent and intense that partners have had to move into a separate bed to avoid waking their partner," Breus says. Sometimes people don't even recall a hypnic jerk and it's the sleeping partner who wakes up and tells them. If this happens to you basically all the time, try to increase your sleep quantity and quality. Instagram: @emofly / Via instagram.com It usually just means you need more (or better) rest. "I suggest eliminating alcohol, reducing caffeine especially closer to bedtime, and trying to get to sleep and wake up at the same time every day," says Breus. And if you feel like these episodes are interfering with your rest and daily life, it might be a good idea to meet with a sleep specialist to explore your sleeping behaviors and patterns. Hypnic jerks usually don't require special treatment, but a doctor can help you figure out how to improve your sleep. You can also check out these sleeping tips from the National Sleep Foundation. Or you can just get used to falling off a cliff in your sleep every now and then. Tap to play or pause GIF Tap to play or pause GIF FOX / Via giphy.com No big deal.