Image: Pexels/Ron Lach

Our three children never appreciated my well-intentioned early morning interventions into their sound sleep. My sing-song “wakey wakey time” suggestion—which invariably led to serious demands and ultimately lots of yelling and arguing before a frantic breakfast and a mad dash to get to school on time—no doubt still haunts their adult dreams.

Now I know better. And with most U.S. schools starting back up this month, parents with kids still in school need to know this, too:

Among the stupidest rituals of modern American society is early school start times that force parents to roust kids out of bed in the predawn. Right behind that on the idiocy scale is waking children on weekends because we, as adults, deem sleeping in to be a sign of laziness. Combined with other challenges to a good night’s sleep, these ingrained inanities cause three-fourths of high schoolers and two-thirds of younger kids to sleep much less than what’s good for them.

Let the kids sleep, science says emphatically. Their body health, brain functioning and overall happiness—even their ability to dream—depends on it.

Lasting deficiencies

This problem is well documented and well understood by sleep experts and pediatricians. Lack of sleep among adolescents and young adults was declared an epidemic in 2014 by the American Academy of Pediatrics:

“Chronic sleep loss and associated sleepiness and daytime impairments in adolescence are a serious threat to the academic success, health, and safety of our nation’s youth and an important public health issue.”

Meanwhile, the evidence of damage to sleep-deprived young minds continues to mount.

Kids ages 6 to 12 who don’t get at least 9 hours of sleep nightly develop lasting deficiencies in parts of the brain involved in memory, intelligence and overall well-being, a new study reveals.

“We found that children who had insufficient sleep, less than 9 hours per night, at the beginning of the study had less grey matter or smaller volume in certain areas of the brain responsible for attention, memory and inhibition control compared to those with healthy sleep habits,” said study team member Ze Wang, PhD, a professor of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine. “These differences persisted after two years, a concerning finding that suggests long-term harm for those who do not get enough sleep.”

The study, published this week in the journal Lancet Child & Adolescent Health, drew from medical records and brain scans on 8,300 children, along with surveys of the kids and their parents at the outset of the research and two years later.

The analysis took into account differences in gender, puberty, socioeconomic status and other potentially confounding factors, and the findings support current recommendations that kids in this age group get at least 9 to 12 hours of sleep per night, Wang and colleagues say.

“Sleep can often be overlooked during busy childhood days filled with homework and extracurricular activities,” E. Albert Reece, MD, a professor and dean at the university’s medical school who was not involved in the study, said in a statement. “Now we see how detrimental that can be to a child’s development.”

The new study is just one of many that reveal damaging effects from lack of sleep in young people (and in adults, too).

Depressed, angry and confused

Sleep studies like the one above often rely in part on self-reporting, which can be flawed. To get around that shortcoming, one small study of 34 teens ages 15 to 17 controlled how much sleep the participants could get during 10 days and 9 nights in a sleep lab.

Teens who were given just 5 hours to sleep each night reported being “significantly more depressed, angry and confused,” compared to those allowed 7.5 hours or more. Those given 10 hours were significantly happier than the teens restricted to 7.5 or 5 hours. Another interesting finding came from the last two nights of the study, when the sleep-deprived teens were allowed 10 hours to snooze in an effort to catch up.

“The two nights of recovery sleep was not sufficient to recover from increased negative mood states for the 5-hour group, although recovery occurred for positive mood states,” said the study’s senior author, Michelle Short, PhD, a research fellow at Flinders University in Australia. “Given the prevalence of insufficient sleep and the rising incidence of mood disorders and dysregulation in adolescents, our findings highlight the importance of sufficient sleep to mitigate these risks.”

Even small changes in sleep duration can have an impact.

Teens who sleep poorly and insufficiently — less than 7.5 hours on weeknights — are more likely to suffer depression compared to those who get 8 hours a night, according to a 2020 study in the Journal of Child Psychology and Psychiatry. The finding is “another piece of evidence to show that there is a significant link between sleep and mental health for teenagers,” said study leader Faith Orchard, PhD, a psychology lecturer at the University of Reading in the UK.

Lack of sleep has other effects that can be less obvious than crankiness or dark circles under the eyes, yet have long-term effects nonetheless.

For example, teens who sleep too little eat 4.5 pounds more sugar during the school year compared to their peers who sleep sufficiently, scientists reported earlier this year.

“Shortened sleep increases the risk for teens to eat more carbs and added sugars and drink more sugar-sweetened beverages than when they are getting a healthy amount of sleep,” said study leader Kara Duraccio, PhD, a clinical and developmental psychology professor at Brigham Young University.

Early school start times have another, perhaps surprising yet insidious effect:

“When teens wake up earlier, it cuts off their dreams,” says Rafael Pelayo, MD, a clinical professor of psychiatry and behavioral sciences at Stanford Sleep Medicine Center. “We’re not giving them a chance to dream.”

What to do, and what not to do

Parents may grow particularly frustrated and confused when their teen’s sleep patterns suddenly shift to a later schedule.

“At the onset of puberty, teens have a circadian rhythm shift, and their body clocks shift to a later schedule,” Lisa Lewis, author of the new book The Sleep-Deprived Teen, explained in an interview with CNN. “It also connects to the release of melatonin, which is what primes our bodies to sleep. When kids become teenagers, melatonin begins to be released later than it used to. That means teens are not ready to fall asleep until 11 p.m. Because the same melatonin does not recede until later, teens end up wanting to sleep in more than they used to.

One of the simplest solutions to this problem—for all school-aged kids and young adults—is later school start times.

When schools start at 7:29 a.m. or earlier, high school students get 46 minutes less sleep per night, on average, compared to students in high schools that start after 8:30 a.m., a study of urban teens found.

“The presumption is if you let kids start school later they will simply go to sleep later and still not get enough sleep,” said study team member Orfeu Buxton, associate professor of biobehavioral health at Penn State. “But that’s a hypothetical scenario. There wasn’t data to back that up.”

Other studies have reached similar conclusions. One also found that with later school start times, students not only get more sleep during the week, but they sleep less on weekends, presumably because they don’t need to catch up.

When school starts later, parents get more sleep, too, other research found.

If your kid isn’t getting enough sleep, you might first try to let them sleep in whenever practical, and consider advocating for later start times in your school district. Otherwise, most kids don’t need any sleep aids. They just need the time to sleep and maybe a little instruction on good sleep habits, like avoiding social media, horror movies or other stressful activities late at night. Their young bodies will take it from there. Whatever you do, don’t let kids take sleeping pills or any other sleep medications unless recommended by a doctor — most are ineffective and can be dangerous.

I’m still on a serious guilt trip about those awful daily “wakey wakey” arguments with our kids. But we’re all sleeping much better now.

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