Here’s what happens to your brain when you don’t sleep

Americans don’t get enough sleep. Even though it’s recommended for adults to log between seven and nine hours per night, most of us never meet that goal. And after a restless night—thanks to our newborn, that late cup of coffee, or work stress—we still pile into our cars or take the train to work. Being productive when our body wasn’t able to properly rest overnight is an uphill battle and one that can have serious impacts on our productivity. But what exactly is happening to our brain the morning after an unintentional all-nighter? Here, experts explain exactly what happens when we don’t get enough sleep. (Spoiler: It’s not great.)

YOU WON’T BE ABLE TO RESPOND IN REAL TIME

You’re yawning over your espresso in a 10 a.m. meeting, and your boss puts you on the spot. Normally, you could talk yourself around the question and come up with an answer, but now, you’re drawing a blank. That’s because lack of sleep has slowed down your alertness and response time, says psychotherapist Jenny Maenpaa. Researchers have connected lethargic behavior and slower mental processing with poor sleep quality, she says, meaning even if you know the answer, it’s hard to access that information when you’re tired.
Sure, you may not be a surgeon or a pilot whose job depends on split-second decisions, but you definitely won’t be able to perform your A game if you regularly miss sleep. “You will still find over time that if your alertness and performance suffer, it is impossible to do your job to expected standards,” she says. “This may be reflected in preventable mistakes, poorly written emails, and reports, or a critical performance review.”

YOU’LL FORGET MORE THINGS

Normally, your to-do list is easy to rattle through, since you have a clear picture of what you need to accomplish and when. But when we’re sleep-deprived, it’s harder to remember. As the therapist and cofounder of The Happy Sleeper, Heather Turgeon explains, when we miss sleep, it leads to reduced brain activity in the regions involved in working memory. This means we can’t hold onto information or think creatively.

In addition to not being able to think about what happened in the past, we also may not be able to remember the sleepless 24 hours we had. “One of the newer lines of thinking about sleep suggests that while we sleep, cerebrospinal fluid flushes certain toxins out of the brain and allows for memory formation,” she explains. “Not getting enough restorative sleep could interrupt the formation of memories. During the day, we might not feel as sharp, and we may not have as clear a grasp on the information we learned the day or week before.

YOUR MIND WILL BE MORE CHAOTIC—AND YOU MAY FEEL ANXIOUS

Many experts believe that falling into a deep enough sleep to dream allows our mind the chance to release negative, stressful energy. “Researchers believe that [dreams] may help us sort through recent intense emotional experiences by creating connections between neurons and allowing us to wake feeling calmer about what we experienced,” Maenpaa says.

Perhaps that’s why advice like “just sleep on it” is so prevalent since rest goes seem to give our mind a clearer perspective. When your brain doesn’t get this time, it may feel overcrowded, and you could struggle to tame your thoughts. Maenpaa says this can lead to increased anxiety that doesn’t diminish over the course of the workday.

YOU MAY STRUGGLE WITH IMPULSE CONTROL

Unfortunately, part of being a professional is learning when and how to pick your battles. However, it’s easier to bite your tongue when your coworker does something annoying when you’re well-rested, says Maenpaa. How come? Our most innate animal instincts come out when we don’t get enough sleep. “All of the strategies we have built over our lifetimes to help us control our primitive emotional reactions are forgotten when we are tired,” she says. “We have slower reaction times, are able to pay less attention to nuances in situations, and have a lowered ability to control our immediate emotional reactions.”

Like a toddler that didn’t get his or her way, we often revert back to this childlike state when we are feeling exhausted or out of control. “Your brain believes that it is engaged in a ‘fight-flight-or-freeze’ situation, and shuts down all nonessential functions that would be unnecessary in a near-death situation,” Maenpaa says. “This internal fire alarm also alters how the brain controls mood, motivation, and fear.”