Why teenagers stay up late, and how to help them get enough sleep

If your teenager can't fall asleep before 11 and can't get up at 6:30, that's mostly biology. Around puberty, the body's internal clock shifts later, so teens start feeling sleepy later at night. Meanwhile they still need 8 to 10 hours, and school still starts early. Parents can't change puberty, but you can protect the hours that are left: phones out of the bedroom, a steady wake time, and less piled onto school nights.

Why do teens get sleepy so late?

Sleep researcher Mary Carskadon has spent decades on this question. In her review "Sleep in Adolescents: The Perfect Storm", she describes two biological changes during puberty. Teens' circadian rhythm, the internal clock, shifts later, including the timing of melatonin release. And the pressure to sleep builds up more slowly across the day, so staying awake late at night feels easier for them than it does for younger kids.

Then add the outside forces: early school starts, homework, sports, jobs, friends online, and phones that never stop buzzing. That's the "perfect storm."

So when your fifteen-year-old says she's not tired at 10 p.m., she's probably telling the truth.

What do schools have to do with it?

A lot. In 2014 the American Academy of Pediatrics recommended that middle and high schools start at 8:30 a.m. or later, so students have a realistic chance at enough sleep. Many schools still start earlier. California became the first state to require later start times, in a law that took effect in 2022.

If your district starts early, this is something parents can bring up with the school board. It's a public-health question, not just a scheduling one.

Why does it matter so much?

The AASM consensus statement found that teens who regularly sleep less than recommended have higher rates of attention, behavior and learning problems, and a higher risk of injuries, obesity, depression and self-harm. Short sleep also makes teen drivers more dangerous. Drowsy driving is a real risk with a new license. Our article on talking to teens about driving covers it.

It also makes everyone grumpier, which nobody needs a study to confirm.

What can parents actually do?

Get phones out of the bedroom at night. Set up a family charging spot in the kitchen, and do it yourself too so it feels fair. This one change helps more teens than almost anything else.

Keep wake-up time steady. Letting a teen sleep until noon on Saturday makes Monday worse. An hour or two later than school days is a reasonable compromise.

Look at the schedule honestly. If practice ends at 8, homework runs to 11, and the bus comes at 6:40, something has to give. Help your teen see the math and decide what to cut.

Morning light, evening dim. Bright light soon after waking and dimmer lights at night help nudge the clock earlier.

Watch the caffeine. Energy drinks and large coffees after school can delay sleep for hours.

Talk to your teen about it as a partner, not a warden. Many are relieved to hear that their late-night alertness isn't a personal failing.

When is it a sleep problem rather than teen life?

See a doctor if your teen can't fall asleep for hours even when tired, snores loudly or stops breathing in sleep, falls asleep in class or while driving, or seems persistently low or hopeless. Sleep problems and depression often travel together, and both are treatable.

Frequently asked questions

Should I let my teen nap after school?

A short nap of 20 to 30 minutes in the early afternoon can help. Long or late naps make it harder to fall asleep at night.

Do melatonin supplements help?

Talk to a doctor before using them. Melatonin isn't regulated like medication in the U.S., doses vary, and it's not a substitute for fixing schedules and screen habits.

My teen says they sleep fine with their phone in the room. Should I believe them?

They may believe it. Try a two-week experiment with the phone outside the bedroom and compare how they feel.