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“Basically everything you do, you do better with a good night’s sleep,” says Dr. Michael Breus, a clinical psychologist and fellow of the American Academy of Sleep Medicine. That may sound like an exaggerated claim your parent would make to get you to go to bed earlier, but he’s not joking—as humans, we have a serious biological need for sleep.

What’s interesting, though, is that researchers still don’t know the whole story behind why we need sleep. From an evolutionary perspective, it doesn’t exactly make sense. It’s one thing to enter into a totally unconscious, semi-paralyzed state when we’re tucked safe in our beds at night, but for our caveman ancestors, sleep meant spending huge chunks of time potentially vulnerable to predators, like say, lions or jaguars on the hunt at night. Considering the risks, sleep must be pretty important.

While researchers haven’t figured out the whole sleep story, science does tell us a lot about what our bodies do better with sleep, and there’s a ton of science behind how a good night’s sleep helps our brains, bodies, and even our emotions perform at their peak. Here’s what the research tells us so far.

Brain icon#1 Sleep keeps your brain working efficiently

Scientists’ leading theory is that our brains need sleep to clean out all the extra information we pick up throughout the day, which helps with memory and learning. According to a 2017 animal study published in Science, the brain appears to pare back unneeded synapses (networks of neurons where we store new memories) during sleep, consolidating our memories and making room for new information.

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Doing well on exams

Getting enough sleep is clutch for your academic goals—it helps you think more clearly during the day. A 2014 study in Social Science & Medicine found that students who got at least seven hours of sleep leading up to an exam scored 8.5 percent better than students who got six hours or less. That 8.5 percent could mean the difference between a B and an A. “Every single thing that you need while taking an exam is affected by sleep deprivation,” says Dr. Breus. “Memory, recall, understanding the question, thinking through the answer, everything.”

“It’s more beneficial to sleep than to stay up until 2:00 a.m. studying because that info won’t be retained fully.”
—Augustine, sophomore, Boston, Massachusetts

Study strategy

We’ve all felt unprepared the night before a test at least once or twice. While not ideal, it happens, leaving you with a dilemma: Do I stay up late and cram, or try to get a good night’s sleep? According to the experts, the better option is a no-brainer. “The number one thing you should never do is pull an all-nighter,” says Dr. Breus. “There’s plenty of data to show that it absolutely won’t help.” A 2012 study conducted by researchers at UCLA found that the more sleep high school students sacrificed to cram in extra study time, the more they experienced academic problems in school the next day (such as struggling to remember information or doing poorly on a quiz). That’s not to say you should skip the studying, but rather than grabbing a latte and preparing for a late-night cram session, it’s better to go to bed and get up a little early to run through your notes a few more times, says Dr. Breus.

Remembering new information

Getting regular sleep is essential for two types of memory: declarative, which allows you to recall that Spanish vocab for your test, and procedural, which helps with motor skills, such as learning a new skill on the soccer field. In a 2012 study of adolescents, researchers found that declarative memory improved significantly when students got a full night of sleep between learning new information and being tested on it.

Avoiding the afternoon slump

Sleeping panda
You know how you’re always struggling to stay awake in your post-lunch pre-calc class? According to experts at Harvard Medical School, that sleepiness has nothing to do with how interesting you find your math book. Your circadian rhythm—aka your body’s internal clock—naturally dips during that time, and the less sleep you’ve gotten, the sleepier you’re likely to feel. The reason for the dip in afternoon energy is likely due to a combination of factors, according to the National Sleep Foundation, such as:

  • What you ate for lunch (simple carbs like white bread or white rice tend to make you sleepier since they cause a sharp spike and then a drop in blood sugar)
  • How long you’ve been sitting still (getting up and moving regularly helps keep you alert)
  • Your core body temperature (it naturally dips in the afternoon, but you can rev it up with exercise or by going for a brisk walk)

Buried deep in the hypothalamus of your brain is a little cluster of cells that dictates your body clock. Your circadian rhythm is programmed to change throughout the day—you feel more alert in the morning and get sleepier as the day goes on.

While getting your circadian rhythm on track with your school schedule can require a lifestyle shift, there is one trick you can use to feel more awake in a pinch (e.g., before a calc quiz or your afternoon class). “One of the best things you can do is go outside and get some direct sunlight,” says Dr. Breus. Between one and three in the afternoon, your brain starts releasing melatonin—a hormone that makes you sleepy. “Walking outside essentially turns that [flow of] melatonin off,” Dr. Breus says. If you can, step outside at lunch or try to sit by a window with some natural light.

Muscle icon#2 Sleep helps your body reboot and recover

It’s not all about your brain. Sleep also helps your muscles relax and recover after a day of working hard. Sleep is like a nightly tune-up, so screwy sleep schedules can result in some bad effects—from athletic injuries to dangerous driving.

Injury prevention

“Sports-related injuries have been shown to be higher in those who get less sleep,” says Dr. Judith Owens, a sleep medicine specialist and the director of sleep medicine at Boston Children’s Hospital. A 2014 study in the Journal of Pediatric Orthopedics found that teen athletes were particularly at risk—those who slept less than eight hours a night were 1.7 times more likely to get injured than those who clocked a solid eight hours or more.

Sports sleep strategy

For student athletes, the key to keeping your game on point is sticking to a schedule, says Dr. Breus. “At the very least, during your season you should maintain a consistent sleep schedule. That means if you go to bed at 10 p.m. during the week, you should do the same during the weekend,” he says. Every time you’re tempted to stay up late watching another episode of Stranger Things, visualize how having a groggy game will feel. If missing the winning shot or getting a season-ending injury doesn’t seem worth it, hit the hay.

“I stay up and watch Netflix or play video games after doing my homework because I don’t want to feel like I spent my entire night just doing work. But then I end up exhausted the next day and too tired to do anything.”
—Tim, senior, Burlington, Vermont

Reaction time

Whether you’re the starting pitcher on the softball team or playing dodgeball in PE class, reaction time is important—and getting enough sleep can make a big impact. A 2012 study of male college students in the Asian Journal of Sports Medicine found that just one night of missed sleep significantly hindered reaction time.

Drowsy driving

“One thing that worries me is drowsy driving,” says Dr. Owens. “The levels of impairment associated with lack of sleep are equivalent to being intoxicated [drunk].” That means driving yourself when you’re sleepy is just as dangerous as it would be to drive after a couple of beers. There are over 100,000 crashes caused by drowsy driving every year, according to the National Highway Traffic Safety Administration. If you’re too tired to drive, pull over for a quick nap, or call someone to pick you up.

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Heart icon#3 Sleep helps you regulate emotions

“Sleep loss significantly affects the emotional brain,” says Dr. Owens. “People who are not meeting their sleep needs tend to have heightened emotions, with less control.”

Risk taking and impulse control

“People who don’t get enough sleep tend to take more risks because they can’t perceive consequences,” says Dr. Owens. In a 2013 study published in NeuroImage, researchers scanned the brains of adolescents and found that sleep deprivation made them more willing to make risky decisions than their well-rested counterparts. Researchers also found that the sleep-deprived students had a higher perception of possible rewards from taking the risks—even if it was false confidence.

Sleep and depression

Chronic sleep loss can also have serious effects on your mental health. “Adolescents who don’t get enough sleep are more likely to report depressive symptoms,” says Dr. Owens. A 2010 study by researchers at Robert Wood Johnson Medical School in New Jersey found that high school seniors were three times more likely to have strong depressive symptoms if they weren’t getting enough sleep, while an additional 30 percent of those in the study showed some signs of depression.

So now you know why sleep is important, but how do you get enough? Check out these 10 ways to step up your sleep.

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Article sources

Michael Breus, PhD, clinical psychologist, diplomate of the American Board of Sleep Medicine, fellow of the American Academy of Sleep Medicine, Los Angeles, California.

Judith Owens, MD, MPH, director of sleep medicine at Boston Children’s Hospital, Massachusetts.

Kelly Glazer Baron, PhD, MPH, sleep researcher and assistant professor in the Department of Behavioral Sciences at Rush Medical College, Chicago, Illinois.

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