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What Pulling an All-Nighter Does to Your Mind and Body

Here's the bare minimum amount of sleep you need before a big exam.
Unsplash/Arthur Savary/Lia Kantrowitz

You had a whole week to prepare for your Comparative Lit exam—but then, well, Assassin’s Creed happened. (Lots of Assassin’s Creed.) Now your only hope is the fallback option that college students have relied upon since the days of affordable tuition: the all-nighter. You go to the common room with two Red Bulls, a bag of books weighing as much as a car tire, and a laptop. You will mentally chain yourself to a desk and finish everything you’ve put off until the sun rises. But then you remember from Psychology 101 that sleep is, like, important. Aren’t you destroying the cognitive capacity you need to get through this year with at least a 2.6 by depriving yourself of it?


Sleep and its role in memory retention

“People tend to overestimate their ability to do things without sleep,” says Emily Papazoglou, an Atlanta-based clinical neuropsychologist. “From a cognitive standpoint, many well-known bad effects come from not sleeping,” she says, adding that lack of sleep negatively affects “attention, how quickly you can react [and] how well you process information.” One study found that a night without sleep gave subjects the cognitive impairment of people who drank to the legal limit.

More importantly for academic performance, sleep helps people retain and utilize information. Although neurologists are still understanding exactly how memories are encoded into the brain, most think it’s a two-step process in which a fact or an understanding is immediately formed and then later encoded for more long-term retention, retrieval, and analysis. The process is called memory consolidation.

Sleep is, like memory, not fully understood. (Scientists are still figuring out the exact reason a person has to go unconscious for hours every day.) But a popular theory is that information taken in during the day is properly sorted into the brain while unconscious. Studies have shown that subjects retain useless information sequences, like numbers or syllables, over a long period of time more easily after a night’s sleep.

All of this is to say that: “Sleep consolidates memory,” according to Alex Dimitriu, a psychiatrist and sleep specialist at Menlo Park Psychiatry and Sleep Medicine in the San Francisco Bay Area. “A lot of what you learn through the day is cycled through sleep.”


During an all-nighter, you may read up on how mitochondria works, but without your hippocampus processing that information into your mind during a sleep cycle, it could be difficult to access it during a test or class discussion.

How best to study instead of sleep (if you must)

Given the rigors of college academic and social life—not to mention the chaotic, cramped environments of dorm rooms and shared apartments—undergraduates may sleep irregularly. “Eight hours is a high goal for a college kid,” Dimitriu says. However, “three or four hours is better than none.”

“It’s a bit of an optimization problem,” he adds, “if you have to read one chapter or get one hour of sleep.” In some cases, it might make more sense to read that chapter.

You might even find that the initial wave of exhaustion passes—thanks in part to stress hormones like cortisol and norepinephrine (adrenaline), says W. Christopher Winter, a board-certified sleep medicine specialist, neurologist, and author of The Sleep Solution. “It’s similar to what people describe when they talk about catching a second wind,” he says. “They have a bit of a surge of energy—your body says ‘wow, we’re doing this.’” Winter also says you might feel your body temperature drop—a trigger for sleepiness. In the short term, that means you might actually feel okay. But don’t be fooled—as sleep-regulating molecules like adenosine accumulate in the brain, the fatigue will eventually overwhelm you, he says. “Sleep always wins out.”


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That’s one reason why the best strategy is always to get some sleep if you can help it, Dimitriu says. It’s believed that REM sleep, the kind that helps consolidate memories and information, can be entered via a brief nap, Winter says. He recommends getting closer to 90 minutes of sleep if you can help it, but even a half-hour power snooze can be healthy as long as you don’t nap to excess or after 3 pm, at which point it may screw up your tiredness and readiness for the next night’s sleep.

How to avoid pulling all-nighters going forward

One of the best ways not to fall into a trap where you’re poring over a textbook at 3 am is to make sleep a part of your scholastic success plan. College is not exactly conducive to good sleep hygiene, but there are still steps you can take.

Earplugs and eyeshades are smart purchases during the pre-dorm move-in Target run, says Michael J. Breus, a clinical psychologist and fellow of the American Academy of Sleep Medicine. Admitting it’s “a bit much” to expect college students to put down their phones and laptops an hour before bed, Breus recommends blue-light googles or glasses for that time. These block out the light frequencies from screens that interfere with the brain’s melatonin supply.

You should also avoid the earliest classes unless you have to take them, Breus adds. Having to get up and schlep across campus for an 8 am class three days a week can throw the rest of the day off, he says.

Caffeine should be avoided in the late afternoon, too—it has a half-life of six hours, Breus says. So keep that in mind when you would like to be feeling less than half the effect of that coffee or Monster Energy Drink.

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