My first encounter with Lisa Lewis was over email, when, in 2017, she reached out about an activist drive to let teenagers sleep.
"I'm excited to let you know about a recently introduced state bill about healthy school start times in California, which would require public middle and high schools to start at 8:30 a.m. or later!" her note read.
School start times may not seem like a political issue apt to mobilize parents, yet every day, for years, they see the effect of school schedules on their children. Two years earlier, Lewis had been no chipper activist — just a mom whose eighth grader started school at 8:45 AM. A year later, as a ninth-grader, her son's school started at 7:30.
"I was driving him to school, and I could just look over and see he was barely awake. And then every afternoon he'd come home, and more often than not, he'd take a nap." The journalist in her took over. After doing some digging, she was alarmed at what she found. "What I quickly realized was this was not (a) a new issue or (b) unique to our community," Lewis told me. "There's a huge body of research about teen sleep."
"Because their body clock shifts at puberty, they're not ready to go to sleep as early as they used to be, and they're also not ready to wake as early."
Back in 1996, a school in Adina, Minnesota pushed its start time later. Fairfax High School in Virginia did the same thing. Seattle Public Schools soon followed. The research on teen sleep was sinking in, at least in some districts. "Hundreds of schools ranging from one to an entire city or county" were getting hip, Lewis said. But the momentum really picked up in 2014, when the American Academy of Pediatrics issued a statement, and 2015, when the CDC released a report on school start times. As Lewis's son was collapsing against the car door before school and into his bed after, "the issue was finally hitting critical mass," she said.
Her work eventually led to an entire book on the topic, "The Sleep-Deprived Teen." After getting a sneak peek, I asked Lewis if I could pick her brain. Our exchange has been edited for length and clarity.
You write that, "School start times can change whereas biology can't." I felt that viscerally, since my daughter will be 13 soon, and every night at 9:00 she gets a second wind and wants to engage right when I'm ready to crash.
That tracks. And it's because their body clock shifts at puberty, and they're not ready to go to sleep as early as they used to be, and they're also not ready to wake as early. Melatonin is being released on a later schedule, and melatonin is what primes us to feel sleepy. Generally speaking, teens aren't ready to sleep until closer to 11:00 p.m. And then if you just do the simple math, they are supposed to be getting 8-10 hours every night, so having to be at their desks at 7 or 7:30 a.m. makes that impossible.
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And this is something we didn't know until relatively recently, right? We just assumed humans need a ton of sleep as infants and taper down until adulthood. But then research showed otherwise?
The Stanford Summer Sleep Camp was held on the Stanford campus from 1976 to 1985, and that's really where a lot of the initial important findings about teen sleep were made. They called them "campers," and they'd take them bowling and play volleyball, but it was a study. The kids had electrodes glued to their skulls. What they found was that actually, kids and teens all needed the same amount: right around 9.25 hours. I spoke with the woman who ran this, professor Mary Carskadon, and to one of the former campers, who is now a grown man. He remembers it being fun!
It must have been for them to keep coming back each year! The topic of fun reminds me of the story of NBA player Andre Iguodala. You wrote that he rehabbed his sleep routine, and his points-per-minute increased by 29 percent! But you make the case that sleep is even more impactful for teens.
First of all, there is nothing positive that comes from being sleep-deprived. It affects your reaction times and your coordination. It increases your risk of injuries. It does nothing to make you a better athlete. In fact, getting enough sleep is what enables recovery from injuries and even just from workouts. When you look at it in the classroom, there's three key ways that being sleep-deprived affects learning: It hampers the process of acquiring new information, the likelihood that they are going to retain that information, and being able to retrieve it when they need to use it. And then on an even more basic level, if you were to walk into an early-start high school, students are asleep on their desks.
What about mental health?
The less sleep teens get the more their suicide risk goes up, which, as a parent, just sends chills down your spine. The odds for a range of risky behaviors go up: substance use, etc. There's a condition called anhedonia, which is where you really just can't derive pleasure from life.
You talk about rates of depression and anxiety being enhanced with sleep loss, and also emotions like fear and anger. On the flip side, you wrote that being well-rested provides an emotional buffer, so fewer fights with parents, more self-control …
Sleep really does boost our emotional resiliency, and it makes it easier to deal with stressors. That's true for all of us, but teens more so than adults. A lot of them outwardly start resembling adults, but they're very much still in development. Their brains are pruning and remodeling. One of the neuroscientists I interviewed compared it to upgrading a dirt road to a paved freeway. At the end of it, teens are able to make better decisions, focus their attention more effectively, and behave less impulsively — but they're not there yet.
So while the road is still being paved, their schedules are different. But many high schools don't accommodate that, with a national average start time of 8:03 a.m. And what surprised me is that 100 years ago, that number was 9:00 a.m.
Yes, school start times have drastically drifted earlier because of consolidation into larger schools and using one set of buses to transport batches of different-aged kids. Who goes earliest? They didn't have that research on the teen sleep schedule and thought, well, high school students are older so they should be the ones. These are legacy schedules. Which is why I'm so excited our law goes into effect on July 1. There are about 3 million kids in public middle and high schools in the state of California, so this is going to have a tremendous impact.
I loved reading about the arguments against moving start times later — like, we won't have daylight left to practice soccer — and what we actually see happen after a shift.
"The bottom line was, when school start times move later, teen crashes go down."
Yeah, there's a natural resistance to change. But when people understand why, that teen sleep deprivation is a public health issue like asbestos or lead paint, it puts it into perspective. Information helps. Studies on schools that have made the switch have not seen any decline in the level of students participating in sports, and the same goes for the effect on after-school jobs, because those tend to be service jobs, the dinner shift.
One of the arguments was that kids are just going to stay up later, that we'll be giving them another hour to mess around online. Do we see that happen?
Kids do stay up slightly later but they more than make up for it by the amount that they are able to sleep in the morning. So going back to Seattle, the largest city to-date to have shifted its start times, they did a pre- and post-survey. Students slept an additional 34 minutes per night. When it comes to sleep research, that kind of improvement is considered huge. And when researchers go back in two years later, the students are still getting that additional sleep.
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It sounds like there are also fewer car accidents. The obvious explanation is that rested teens have better judgment and reaction times, but you mentioned another theory: that a later dismissal just narrows the window of time they're on the road.
Yes, and the bottom line was, when school start times move later, teen crashes go down.
Another piece of this puzzle that grabbed me was the notion that not all teens are affected the same way. You talked about disparities around adolescent sleep.
Biological females take longer to fall asleep than boys and men, they have a higher risk of insomnia, and this all starts in puberty. Their sleep can be affected by hormones and monthly menstrual pain. Then you also have the issue that sexual minority teens sleep worse. And that's a pretty large group. In the most recent Gallup poll, more than 20 percent of the Gen Z respondents said they identify as LGBTQ, higher than any other generation surveyed.
And that's because experiencing discrimination and lacking a sense of belonging makes it harder to sleep?
That's what one researcher thinks is driving this. The issue of discrimination is also something that comes up when you look at teens of color who are disporoprtionately likely to have trouble falling asleep and feel sleepier the next day. And that's everything from microaggressions on up. There's also the whole issue of socioeconomic impact. If you are in crowded living conditions or if where you live is noisy, or if you don't feel safe, or if you are hungry when you are going to bed, all of those can impact sleep.
That makes so much sense. I want to go back to gender for a second and talk about socialization, because not all of the disparity is biological. You quoted psychologist Lisa Damour saying girls tend to co-ruminate, going over issues again and again via Facetime or Snapchat, and all that talking can keep a problem alive.
Yes, absolutely. And the issue of social media and tech is a huge one, too. There are three ways that tech impacts sleep: (1) it literally takes time away from sleeping, (2) the stimulating interaction, which is the piece you were just talking about, and (3) the impact of blue light. We hear a lot about blue light, and we definitely need to dim our lights, but the people I spoke with really thought light was probably the lesser of those three. It's more that if you are up until 1:00 AM playing video games, of course that disrupts your sleep time.
And it also displaces things that could be calming before bed, right? If you are on your phone, you're not taking a warm bath.
A wind-down routine is really important. We are not like computers, we can't just flip off the switch and boom, you fall asleep. The official recommendation is no tech at least an hour before bedtime.
But you also wrote, "Even if teens were to chuck their smartphones … it's likely they still wouldn't be able to get enough sleep, given how early they have to wake to get to school on time." A lot of the advice we get these days focuses on improving our personal habits. And your message is that there's room for that, but you go back to structural issues.
Yes. Studies show that teens at earlier starting schools are getting to bed earlier than their peers at later starting schools, but they're still getting less sleep. So it just goes to show that there's only so much you can do. Groups like Start School Later have been involved in advocacy for this since 2011. It's a straightforward change that doesn't put the onus back on families.
And individuals reading this can help, right? A lot of the stories you recounted in the book are about parents like you who said, "This sucks," and then went to a board meeting, formed a local group, or wrote to their state legislators.
Absolutely. And getting back to mental health, sleep is one specific thing that we can do to help our teens. So much of the rest of what is going on is out of our control, but we can help them get more sleep.
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