Why Are You Groggy in the Morning?

Even if you’ve had seven or eight hours of sleep, when that alarm goes off or your eyes blink open first thing in the morning, you may still wake up feeling sluggish and disoriented.

Unlike a brand-new Porsche that can go zero to 60 nearly immediately, we’re more like a beat-up — but beloved — old Chevy that takes a few turns of the ignition before our engines really rev up. 

Even when you’re in tip-top shape, you might struggle with grogginess in the morning. So what’s going on?

Waking Up Tired

That groggy feeling has a name: sleep inertia. Despite most people experiencing it on a daily basis, scientists don’t know exactly what causes it. However, brain studies show that some features of being asleep persist even after you wake up. It’s theorized that this is a protective mechanism that makes it easier to fall back asleep if you wake in the night.

Not all parts of the brain warm up at the same time, either. You may get yourself to stand up and walk down the hall, but you probably couldn’t do your taxes in the moments after you wake up. Your prefrontal cortex — the part of the brain responsible for decision-making, emotional regulation, and working memory, appears to take the longest to get going.

There are two main signs that tell scientists your brain takes some time to fully catch up with your body in the morning. One is that the brain continues to emit delta waves — the slow-wave frequency your brain typically produces during deep sleep. 

The other involves adenosine, a chemical that builds up in your brain while you’re awake that promotes drowsiness, so you’ll want to sleep at night. The longer you’re awake, the more it builds up, making you more tired as the day wears on. This natural tranquilizer decreases while you sleep, but some scientists believe that when you wake, your adenosine level hasn’t fully “cleared” yet. That means you could be drowsy even after a full night’s rest.

This also helps explain why you’re especially tired when you don’t get enough sleep — you didn’t give your brain enough time to deplete its adenosine. It’s also why coffee wakes you up, as caffeine physically blocks the adenosine receptors in your brain.

Sleep inertia can occur when you wake up from an afternoon nap of more than 30 minutes, but it’s more likely seen after a night’s sleep. It causes reduced awareness, a decline in performance, difficulty making decisions, and a strong desire to return right back to sleep (we all know that one). These feelings usually go away after 30 minutes, but can last as long as two hours.

These Conditions Don’t Help

While sleep inertia is a normal part of waking up, some conditions can make it last longer, including sleep deprivation, insomnia, depression, stress, and drinking alcohol or caffeine before bedtime. Suboptimal sleep environments, such as bright, noisy, or hot rooms, may wake you up many times in the night without you realizing it, contributing to inertia.

You may also be out of sync with your own chronotype, your natural sleep preference. For instance, you may be a night owl but have to get up each morning at 7 a.m. for work. 

The best way to think of grogginess in the morning is that it’s a (hopefully brief) transition phase from being asleep to being awake. And because it’s a transition, that means it’ll soon pass and you’ll be bright-eyed and ready to get your day going — assuming, of course, you went to bed on time and got a good night’s sleep in the first place. You did go to bed on time, right?