A 17-year-old should get 8 to 10 hours of sleep every 24 hours. That’s the recommendation from the American Academy of Sleep Medicine for all teenagers ages 13 to 18. Yet in 2023, only about 1 in 4 high school students reported getting at least 8 hours on a typical school night, according to CDC survey data. The gap between what teens need and what they actually get is one of the most consistent findings in adolescent health research.
Why Teens Fall Asleep Later
If your 17-year-old can’t seem to fall asleep before 11 p.m. or midnight, that’s not laziness. It’s biology. During puberty, the body’s internal clock shifts later in a process called phase delay. A teenager’s internal clock runs on roughly a 24-hour-and-16-minute cycle, compared to about 24 hours and 7 minutes in adults. That difference sounds tiny, but it accumulates, pushing the natural sleep window later each night.
On top of that, the teenage brain responds differently to light. Compared to younger adolescents, older teens are less sensitive to morning light (which normally helps reset the clock earlier) and more sensitive to the phase-delaying effects of evening light. The result is that a 17-year-old’s brain starts releasing the sleep-promoting hormone melatonin later at night than it did a few years earlier. This makes early school start times especially punishing: teens are being forced awake during what their biology treats as the middle of the night.
What Happens When Teens Don’t Get Enough
Grades and Focus
Sleep and academic performance are tightly linked. High school students who sleep fewer than 7 hours are roughly twice as likely to report grades of C or worse compared to peers who sleep longer. Taking more than an hour to fall asleep nearly triples those odds. These effects stack: the more sleep-related risk factors a student has (short sleep, early wake times, difficulty falling asleep, waking during the night), the worse their reported performance.
Weight and Metabolism
Sleep-deprived teens tend to eat more without burning more energy. Studies show this leads to increases in body fat and BMI over time. In adults, the mechanisms are well established: short sleep disrupts the hormones that regulate hunger and fullness, making high-calorie food more appealing. Researchers believe the same processes are at work in adolescents, creating a cycle where poor sleep promotes weight gain, which can further disrupt sleep quality.
Mental Health
The mental health consequences are stark. Chronic sleep problems during adolescence increase the risk of developing depression by roughly 1.7 to 2.3 times, depending on the study. Combined sleep issues, including insufficient sleep and disrupted circadian rhythms, raise the risk of mood disorders even further. There is also a dose-response relationship between sleep loss and suicidal thinking: for every one-hour decrease in sleep duration, the risk of making a suicide plan rises by about 11%. These aren’t small effects, and they underscore why consistent, adequate sleep is a genuine mental health priority for teens.
Screen Time and Falling Asleep
Blue light from phones, tablets, and laptops delays sleep onset, but the timing matters more than most people realize. In a study of young people, blue light exposure between 10:30 p.m. and midnight pushed sleep onset to about 31 minutes on average, compared to 20 minutes with no exposure. Earlier evening screen use (before 9 p.m.) had almost no measurable effect on how quickly people fell asleep. So the practical advice isn’t necessarily “no screens after dinner.” It’s to put screens away in the last hour or so before your intended bedtime.
Weekend Catch-Up Sleep: Helpful but Limited
Many teens try to compensate by sleeping in on weekends. This isn’t entirely useless. One large study found that late adolescents and young adults who got extra weekend sleep had 41% lower odds of daily depressive symptoms compared to those who didn’t catch up. But the same research found that simply getting a healthy amount of sleep on weekdays, at a consistent time, provided twice the benefit. Weekend recovery sleep is a band-aid, not a solution, and large swings between weekday and weekend schedules (sometimes called “social jetlag”) can make it harder to fall asleep on Sunday night, restarting the cycle.
Practical Ways to Get Closer to 8 Hours
A 17-year-old who needs to wake up at 6:30 a.m. for school would need to fall asleep by 10:30 p.m. at the latest, and that’s for the bare minimum of 8 hours. Since most people take 15 to 20 minutes to fall asleep, being in bed by 10:00 or 10:15 is more realistic. For teens whose biology is pushing them toward a later sleep window, a few strategies can help close the gap:
- Morning light exposure. Getting bright light within the first 30 minutes of waking helps shift the internal clock earlier over time, even though teens’ sensitivity to morning light is reduced during puberty.
- Screen curfew after 10 p.m. Since late-night blue light has the strongest effect on delaying sleep, setting screens aside by 10 p.m. makes a measurable difference in how quickly you fall asleep.
- Afternoon naps, done right. Johns Hopkins Medicine recommends a 30- to 45-minute nap before dinner for sleep-deprived teens. This is more effective than sleeping in on weekends because it doesn’t disrupt the body’s overnight sleep cycle.
- Consistent schedule. Keeping bed and wake times within about an hour of each other, even on weekends, reduces the social jetlag effect and makes it easier to fall asleep on school nights.
The 8-to-10-hour window isn’t arbitrary. It reflects the amount of sleep the teenage brain needs to consolidate learning, regulate mood, and support the physical changes still happening at 17. Most teens won’t hit 10 hours on school nights, but consistently reaching 8 is a realistic and meaningful target.