You’ve probably experienced sleep deprivation as an adult. You know how it feels to wake up in the morning, groggy, and drag yourself through the day. You’ve probably encountered “microsleeps,” those brief moments when your mind lapses into unconsciousness. You know what a struggle it is to stay alert, to pay attention. You remember the overall sensation of fatigue and illness. And you doubtless remember how sleeplessness erodes your emotional well-being.
But what about kids? What are the signs of sleep deprivation in children and teens? When young people aren’t getting enough sleep, they often display the same symptoms we observe in sleep-deprived adults:
- It’s hard to awaken them in the morning.
- They’re prone to falling asleep spontaneously during the day — taking unplanned naps.
- They experience poor moods or irritability, and have more trouble controlling their impulses.
- It’s difficult for them to pay attention or concentrate. Reaction time is impaired.
- They show reduced interest or curiosity in learning.
- Their thinking processes may seem sluggish, distracted, or confused.
- On weekends or holidays, they “sleep in” late — the body’s attempt to catch up with a sleep debt accumulated during the school week.
These, at any rate, are some of the most immediate signs — the symptoms you may observe in the short-term. What happens over the long-term — when kids routinely or habitually skimp on sleep?
According to a recent national survey, 36% of American kids, ages 6 to 12, aren’t getting enough sleep. Nearly 32% of U.S. teenagers aren’t getting adequate sleep (Tsao et al 2021). And studies suggest that kids with chronic sleep loss are at higher risk for:
- beginning elementary school with reduced school readiness (Tso et al 2016);
- suffering injuries that require medical attention (Obara et al 2021);
- experiencing more aches, pains, and gastrointestinal distress (Krietsch et al 2020);
- failing to do their homework (Tsao et al 2021);
- gaining excessive weight during childhood (Yu et al 2021; Lumeng et al 2007); and
- experiencing psychological problems with anxiety, depression, aggression, or rule-breaking (Vermeulen et al 2021).
So if a child is habitually skimping on sleep, there’s a lot more at stake than feeling a bit grumpy, drowsy, or otherwise out of sorts. In the rest of this article, we’ll delve deeper into what studies tell us about the social, emotional, and cognitive costs of poor sleep.
The socio-emotional signs of sleep deprivation
Across a variety of studies, researchers confirm what we know from everyday experience. People suffering from sleep loss tend to experience negative moods (Tomaso et al 2020).
The link is evident as early as infancy. Babies who get less total sleep across a 24-hour period are more likely to develop symptoms of anxiety and depression during their toddler years (Mindell et al 2017).
It’s also clear that sleep and emotionality are linked among older children and teens (Sheik and Buckhalt 2005; Vriend et al 2015).
Of course, correlation doesn’t prove causation. If a child is having emotional difficulties, we can’t assume that sleep is to blame. Things can work in the opposite direction, too, with emotional problems making it harder for a child to fall asleep or stay asleep.
Moreover, studies suggest that certain genes have overlapping effects — simultaneously putting kids at higher risk for both sleep problems and emotional difficulties (Miadich et al 2020; Vermeulen et al 2021). So it’s complicated.
However, we have good evidence to support the idea that restricted sleep has harmful effects on socio-emotional functioning.
Young volunteers have participated in sleep restriction experiments, where researchers impose different sleep schedules on kids, and then look for effects on behavior. And the results strongly suggest that sleep loss has an impact on emotional regulation.
For example, in a study of 50 teenagers (ages 14-17), researchers forced kids to cut back on sleep by approximately 2.5 hours each night. The change led to increases in irritability and tension, with kids reporting higher levels of anger, resentment, and spite. In addition, they had difficulty reigning themselves in, “leading to emotional outbursts and exaggerated responses to small triggers” (Baum et al 2014).
Another experiment restricted adolescents to an average of only 4 hours per night, and found that kids subsequently expressed more negative emotions toward their friends during a live conversation (McMakin et al 2016). In a third study, teens restricted to 4 hours of sleep experienced a big dip in positive emotion, and a marked surge in anxiety (Reddy et al 2017).
And what about younger children?
Even modest sleep loss can trigger emotional problems in school-aged kids
In one study, researchers altered the sleep patterns of 32 elementary school students, ages 8-12. Each child lived through two, different treatments:
- During one week, kids experienced 4 consecutive days on a restricted schedule, sleeping approximately 45 minutes less than usual.
- During another week, kids spent the same number of days on an enhanced schedule — sleeping nearly 30 minutes longer than usual.
So researchers were able to directly compare the difference between restricted sleep and enhanced sleep for every participating individual. And the results were clear: Under conditions of sleep restriction, kids struggled more to control their negative emotions. In addition, they experienced less happiness and interest in things (Vriend et al 2013).
That’s a pretty concerning finding, especially given that about one third of U.S. school children aren’t getting enough sleep (Tsao et al 2021). And a recent experiment by Fiona Davidson and her colleagues is even more eye-opening.
These researchers tested the responses of 6- to 11-year-olds to a really small reduction in sleep time — just 20 minutes per night. As it turns out, that, too, was enough to have a noticeable impact on children’s emotional well-bring. After only 6 days on this restricted sleep schedule, children experienced more mood swings — rapid and extreme emotional changes (Davidson et al 2021).
Are some kids more at risk for the emotional effects of sleep deprivation?
Yes. For example, experiments suggest that sleep restriction has a more dramatic impact on the emotions of kids who struggling with attention deficit hyperactivity disorder (Becker et al 2020). It also appears that the emotional effects of sleep loss are more intense for children with pre-existing anxiety problems (Alfano et al 2020).
What about stress? Do sleep-deprived kids respond differently to stressful social situations?
Yes, that seems a sure bet. As we’ve already seen, one study found that sleep-deprived teens reacted more negatively to a conflict discussion with peers. And experiments suggest that sleep deprivation alters brain activity in adults and children alike — making neural regions that process emotion more reactive in response to potentially threatening social stimuli (Reidy et al 2016; Gordon et al 2017).
The cognitive signs of sleep deprivation: More than just impaired reaction time
Something flashes briefly on a screen. Did you notice? How quickly can you react? This is the basis for the psychomotor vigilance task, a test that psychologists use to measure alertness and reaction time. And unsurprisingly, sleepless people perform worse on this test: Impaired reaction time is a well-attested sign of sleep deprivation (deBruin et al 2017).
It can get us into plenty of trouble — danger, even, if we’re driving a vehicle. So we’re often warned about it. But this isn’t the only cognitive symptom triggered by sleep loss. It isn’t even the only symptom that undermines our ability to pay attention.
Take, for example, the case of mind-wandering. We’ve all experienced it at one time or another — a spontaneous mental shift away from the task at hand. But for some children, mind-wandering happens a lot. They can’t seem to help it.
We might assume the difference comes down to a quirk of personality. Yet that isn’t what researchers find. In a study of more than 520 kids, aged 6 to 18, Karen Spruyt and her colleagues tested for mind-wandering during a computerized attention task. They found that nearly half the differences between individuals mapped onto differences in sleep patterns, including how much total time a child spends in bed (Spruyt et al 2018).
Then there’s working memory capacity. Working memory is the mental “notepad” we use to keep certain information active while we’re thinking or solving a problem. As I explain elsewhere, working memory capacity is pretty limited under the best of circumstances, but sleeplessness makes it worse.
For instance, a recent study assigned 36 healthy teenagers to experience a series of different sleep schedules, including a week of sleep restriction (6.5 hours per night) and a week of healthy sleep (9 hours per night). And sleep restriction took a clear toll: Teens showed working memory impairments on the hardest task level (Alsameen et al 2021).
And what about the overall speed of processing? The time it takes the mind to perform an arithmetic calculation, or solve a puzzle, or think of the answer to a teacher’s question? If you consider the symptoms we’ve mentioned so far — impaired reaction time, mind-wandering, and working memory problems — it’s easy to understand how sleep loss could shift your brain into slow-motion.
June Lo and her colleagues wondered about this, especially in the context of adolescents who live a sleep-restricted lifestyle. These kids will typically cut back on sleep during the school week, and then try to sleep longer on the weekends to get caught up. What effect does this lifestyle have on their cognitive abilities?
To find out, the researchers put healthy teenagers through a cycle of sleep restriction and recovery — five consecutive nights of sleep restriction (only 5 hours in bed), followed by two nights of recovery (9 hours in bed).
They also gave kids a battery of tests, measuring changes in psychomotor vigilance, working memory performance, and speed of processing. What were the results?
Throughout the period of sleep restriction, kids performed worse on all cognitive tasks. And that “weekend” recovery sleep? It helped. But even after two nights of recovery, their performance was still worse than it had been before they started the regimen of sleep restriction.
Even more ominous was what happened next, because the experiment wasn’t over. Immediately after the two recovery nights, kids resumed the sleep-restricted schedule for an additional three days. It was a simulation of real life, where kids skimp on sleep from Monday to Friday, try to catch up over the weekend, and then go back to their sleep-restricted ways.
And the results weren’t very reassuring. During that second round of sleep-restricted nights, kids experienced even greater cognitive deficits than they had during the first week of sleep restriction (Lo et al 2017). It paints a gloomy picture for kids who — in the real world — skimp on sleep for weeks at a time.
So what can we do about sleep loss?
There’s actually a lot that parents can do to support healthy sleep.
First, if your child is very young — an infant — you might be wondering how to read your baby’s signals. This Parenting Science article can help you identify the opens in a new windowsigns of sleep deprivation in babies.
Next, if you find your family embroiled in bedtime conflicts — or your child simply has trouble falling asleep at bedtime — my guide to trouble-shooting bedtime problems is a good place to start. It will help you decide what needs to change, and it will lead you to other Parenting Science articles for making the necessary changes.
And for more information about the science of sleep, check out these Parenting Science pages.
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This article replaces a previous article written by the same author with the same title.
Image credits for “Signs of Sleep Deprivation”:
Title image of tired boy by dima_sidelnikov / istock
image of tired girl student in classroom by diego_cervo / istock
Content last modified 11/2021