12 Signs of Sleep Deprivation You Need to Know, According to Experts

Knowing when you’re overtired isn’t exactly rocket science. You probably feel sluggish, weak, and unproductive. Your pesky under-eye circles may be more pronounced, and your cravings, stronger than ever. These characteristics are frequently attributed to sleep deprivation, a condition that happens when you don't get enough sleep, according to the National Heart, Lung, and Blood Institute (NHLBI)— but they're not the only indicators that something's up. Here, experts explain 12 different signs of sleep deprivation, and what you need to know about them. 

"If the brain is not getting the energy it needs from sleep it will often try to get it from food," Chris Winter, MD, owner of Charlottesville Neurology and Sleep Medicine in Virginia tells Health. Running low on rest can increase the production of ghrelin, also known as the hunger hormone, in your gut (although its functions span well beyond regulating hunger). Too much ghrelin makes your body crave fatty and sugary foods, Dr. Winter says. Additionally, a 2008 study published in the Journal of Sleep Research showed that after just one night of sleep deprivation, ghrelin levels had acutely increased in the nine “normal-weight healthy men” participating in the study. Poor sleep can also mess with leptin, the satiety hormone. "When you're not sleeping properly you tend to eat more of what you're craving because you're not feeling the signals to stop eating," Dr. Winter says.

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With an increased appetite comes another unpleasant symptom of sleep deprivation: weight gain. "When you're tired, you don't watch what you're eating," Dr. Winter says. "You just look for all kinds of things to help you feel more awake." With ghrelin and leptin already out of whack, your body will crave fried foods and sweets to get you through the day—a surefire way to widen your waistline. A lack of sleep can also have direct effects on your metabolism, Dr. Winter says; it tends to slow down without proper rest. What's more, a 2012 study in the Annals of Internal Medicine found that just four and a half hours of sleep for four days straight can reduce your fat cells' ability to respond to insulin, the hormone responsible for regulating energy, by 30%.

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People tend to act without thinking when they're exhausted, says Gail Saltz, MD, Health's contributing psychology editor. "Your ability to say, 'No, I shouldn't have another candy bar' becomes more difficult."

This doesn't just apply to eating more—you might also find yourself doing or saying things you don't necessarily mean, like lashing out at a spouse or ranting at a co-worker. "The main thing is you're less inhibited," says Kelly Baron, PhD, a clinical psychologist with specialty training in behavioral sleep medicine tells Health.

That’s because, as research shows, sleep deprivation enhances your impulsivity to negative stimuli, meaning you react before you’ve actually processed the situation or information in front of you. A 2007 study in the journal Physiology & Behavior examined the effects of sleep deprivation on impulse behavior in men and women. Researchers found that patients with impulse control disorders often reported sleep problems, and in healthy individuals, lack of sleep impaired their cognition, decision-making and changed how they weighed risk. Risk-taking as a behavior, decreased in sleep-deprived women, but remained the same in sleep-deprived men.

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If you grew up being told not to stay up late the night before a big test, your parents knew what they were talking about. Studies show that sleep deprivation has a negative impact on memory function.

Specifically, being overtired stops protein synthesis from occurring in the hippocampus section of the brain, which controls memory, learning and emotions. According to a 2012 report by the journal of Behavioural Brain Research, sleep deprivation induces oxidative stress (an imbalance between free radicals and antioxidants in your body), which further impairs learning and memory processes. These experts demonstrated that using Vitamin E, which is a strong antioxidant, counteracted the negative impact of sleep deprivation on memory function (also referred to as chronic sleep deprivation-induced cognitive impairment).

All that being said, if you want to strengthen your memory, you need adequate sleep.

If you've been finding it harder than usual to manage projects at work and home, lack of sleep could be the culprit. "Sleep deprivation can affect speed and higher-level cognitive processing," Baron says. That means essential functions, like problem solving or time management, become even more difficult to carry out.

Take this 2009 study in Sleep: Researchers asked both sleep-deprived and well-rested volunteers to perform a set of tasks that required quick decision-making two times. Between testing, the accuracy of those without quality sleep went down by 2.4%, while the rested group improved accuracy by 4.3%. Simply put, poor sleep hinders your ability to react quickly, and make clear decisions.

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Yes, tripping over a step might make you a klutz. But do it a few times in a day and it might just mean you're too tired to really focus on where you're going.

A 2014 study published by the National Institutes of Health, suggests that acute sleep deprivation negatively impacts subsequent motor and reversal learning and memory. Meaning, "when you're tired, there's a lapse in how you neurologically function in general," Dr. Winter says. With lowered reaction time and concentration also comes more difficulty with movement. "When you walk up and down the stairs, there's a lot of processing going on there," Dr. Winter says. "When sleep deprived you can't process particularly well."

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You might feel like your emotions are out of control when you're sleep deprived. "You become over-reactive to emotional stimuli," Baron says. So things that normally haven't gotten you worked up in the past—a tear-jerking movie or big work deadline—may provoke anxiety, sadness, or anger. (It could also go the opposite way: "People can get slap-happy and giddy as well," Baron says.)

Additionally, a 2008 study in the journal Sleep Medicine shows that lack of proper sleep not only makes you more emotional, it makes you less emotionally intelligent and lessens your constructive thinking skills. This means you’re less able to express, control or even be aware of your emotions.

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Another thing that can suffer with poor sleep is your immune system. "If you're not sleeping properly there can be significant issues in terms of your body's ability to fight off infections," Dr. Winter says. In particular, you might find that it's harder to shake off a cold. A 2009 study in the Archives of Internal Medicine followed the sleeping habits of 153 volunteers for 14 days straight. Researchers found that people who got less than seven hours of sleep were nearly three times as likely to develop a cold than those who got eight hours or more rest a night. That could be because your immune system produces cytokines while you sleep, which are proteins that help protect against infections and inflammation, meaning a few nights of poor sleep could lower your body's defenses against pesky viruses.

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"When fatigued, you're not able to control the muscles of the eye as well," says Steven Shanbom, MD, an ophthalmologist in Berkley, Mich. First, skimping on shuteye tires out the ciliary muscle, which helps your eyes focus. The result: you'll have a harder time reading up close, he says. Light can also affect the ciliary muscle. A 1999 NIH study showed a strong correlation between children who slept with the light on and near-sightedness later in life. While most adults sleep in total darkness, modern blue-light technology like TVs, computers, and cell phones can also contribute to poor sleep.

Then there's the extra ocular muscle, which moves the eye from side to side and up and down. "Many people have a muscle imbalance where their eyes don't track well together," Dr. Shanbom says, but in a well-rested person the eyes can compensate on their own. A lack of sleep makes the misalignment harder to control, potentially resulting in double vision. You might notice both of these vision problems after one night of poor sleep, but they will persist the less time you spend in bed.

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Of all the places on your body, your face can truly show your age if you don't take steps to keep your skin healthy. Those steps include common precautions such as maintaining a well-balanced diet rich in good fats, using UV protection, and perhaps most obvious, getting a good night’s sleep. In a 2014 Clinical and Experimental Dermatology study, experts found that poor sleepers had higher levels of trans-epidermal water loss, thus aging their skin more than good sleepers. Additionally, good sleepers had 30% greater skin barrier recovery, and had a better perception of their appearance and physical attractiveness compared to poor sleepers.

“When a good night’s sleep is hindered, you will look significantly more fatigued,” Flora Kim, MD, FAAD of Flora Kim Dermatology tells Health, citing dark under-eye circles, saggy eyelids, wrinkles or fine lines, droopy corners of the mouth, and paler skin. She says sleep deprivation can also cause occasional acne because it leads to circadian disruption, which translates to an abrupt biological change that creates an imbalance in your skin.

Sleep-deprived people tend to offset their fatigue with increased caffeine intake and/or smoking, which can both contribute to occasional acne. “Your body [also] produces collagen while you’re sleeping,” Dr. Debra Jaliman, MD, a board-certified dermatologist and assistant clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai, tells Health. “Getting enough sleep helps skin restore itself,” she says. “The cells regenerate, and DNA repair is also boosted during this period.”

When you nod off for a few seconds without even knowing, it's called micro-sleep. "The brain says, 'I don't care what you want to do. We are going to sleep,'" Dr. Winter says. It's your body's way of forcing you to get the rest you need. The big problem is that micro-sleep can be extremely dangerous if you happen to be driving. Between 2005 and 2009, the National Highway Traffic Safety Administration estimates that 2.2% to 2.6% of total fatal crashes involved drowsy driving. If you ever feel overly sleepy on the road, a safer bet would be to pull over and rest until you feel up to taking the wheel again.

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Adequate sleep and successful growth go hand and hand. That’s why babies sleep so much the first few years, because their bodies are undergoing rapid growth. Research shows that this trend continues into childhood and adolescence. Generally, children ages 5 to 10 years old need 10 to 11 hours of sleep, and those ages 10 to 17 need about 8 to 9 hours, per the Nursing Management journal. “The human growth hormone (HGH) kicks in while we are sleeping,” says Dr. Jaliman, adding that this is responsible for speeding up skin's repair and cell regeneration.  

A 2009 study in the Journal of Clinical Endocrinology & Metabolism confirms that compared to awake levels, circulating concentrations of growth hormones significantly elevate while sleeping. The means a lack of sleep leaves you with fewer growth hormones, thus stifling your growth and development. So, if you want to give your growth plates the best chance possible, get lots of rest.

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