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Parents of teens know this familiar sight: Waking in the middle of the night, maybe to go to the bathroom, and looking down the hall and seeing a line of light under their teenager’s door.

But remember what life was like when you were coming of age. Late nights define young adulthood. Rites of passage: sleepovers, Saturday Night Live, falling asleep in class.

Easy to joke, but now kids have screens in-hand well past bedtime. And now we’re better understanding the biological underpinnings of why adolescents and young adults naturally feel sleepy later and prefer waking later. The catch: Despite this shift towards being “night owls,” adolescents require more sleep than younger children or adults, which can lead to sleep deprivation and accumulating sleep debt when early school and work schedules clash with circadian changes.

New research is exploring why some young people are more likely to stay up later than others, and when it can be problematic rather than having some benefit. And studies are increasingly linking a chronic lack of sleep in adolescents to significant health challenges, from impaired judgment and risky behaviors to a heightened risk for depression and anxiety.

The Kids Have a Rhythm All Their Own

A key factor in sleep changes during adolescence and young adulthood is a biological delay in the circadian rhythm, which naturally pushes young people to feel sleepy later and prefer waking later, said Steven Carlson, a graduate student in clinical psychology at the University of Utah, Salt Lake City, Utah, and co-author of a new study linking teen bedtime procrastination with negative behavior and outcomes.

He noted that this is compounded by alterations in the homeostatic process, often described as a “hunger for sleep.” While staying up later typically builds this sleep drive, making it easier to fall and stay asleep, this buildup occurs more slowly in adolescence. 

This means young people can remain awake longer into the night without feeling overwhelmingly tired, further contributing to their delayed sleep patterns, noted Carlson. These changes are so consistent that scientists can come close to predicting a teenager’s “biological midnight,” or the time their sleep hormone melatonin peaks, simply by knowing their age.

Because of these puberty-linked sleep changes, in 2014 the American Academy of Pediatrics began recommending high schools start no earlier than 8:30 AM. Yet, as of 2020, the average start time across the country was 8:00 AM.

These puberty-linked changes and early start times create a “perfect storm” of insufficient sleep for adolescents that can lead to a host of negative consequences, explained Riya Mirchandaney, a doctoral candidate in clinical-health psychology at the University of Pittsburgh, Pittsburgh. She studied the characteristics of adolescents who are most likely to develop risky behaviors due to lack of sleep.

Mirchandaney’s research, which included 210 adolescents who completed surveys and wore an actigraphy watch for 2 weeks to measure sleep patterns, found that those who identify as “night owls” tend to be more impulsive. They reported higher “negative urgency,” or acting impulsively when upset, and a lack of perseverance, often quitting difficult tasks. She noted that impulsivity is a known contributor to alcohol and substance use, putting these “night owls” at particular risk.

A late chronotype can be entirely normal, but when paired with a disposition toward rash decision-making and chronic short sleep, it becomes a potential gateway to high-stakes experimentation — drinking, speeding, or unprotected sex — that the fully rested brain might resist. Mirchandaney said her results could influence future research to help teens avoid the negative effects of impulsivity, perhaps through sleep interventions.

Stay Up Late, Everybody’s Doing It

There’s also a powerful, often healthy, social draw at night. Young adults and adolescents feel a strong urge to connect, belong, and spend time with friends. Joshua Gooley, PhD, an associate professor with the Neuroscience and Behavioural Disorders Programme at Duke-NUS Medical School in Singapore, studies bedtime procrastination, or going to bed later than intended, despite knowing that on the next day you might suffer some negative consequences. 

The focus of Gooley’s latest study was how staying up too late correlated with the need to belong. He and colleagues enrolled 104 students to collect data over a 2-week period, including actigraphy watches to measure their sleep/wake patterns, proximity sensors to see if they were close to other study participants, and diaries to record whether they stayed up later than intended. If they stayed up late because of friends, they asked the participants to write down who kept them up. 

They found that when college students stayed up late for in-person social events, their sleep was, on average, cut short by more than an hour. Those most at-risk for staying up late to socialize were those who scored higher on both extraversion and need to belong, Gooley said. They also identified “bedtime influencers” who tended to keep other students up.

In middle school, high school and college, “there’s this real, strong need to belong, to be part of the group, to be a part of the community. And I think that’s probably going to be driving communications that extend beyond a person’s usual bedtime,” said Gooley.

But while there are some benefits to socializing, Gooley said, “we’ve looked at next-day morning mood and next-day sleepiness, and our students are worse off on the following day when they do this.”

And not all bedtime procrastination offers social rewards. Carlson studied 390 college students who completed surveys and a 2-week sleep diary to observe the personality traits of those who procrastinated their bedtime.

He expected a delayed bedtime could be a pleasurable experience — time to do enjoyable things before bed. However, their results indicated that delaying bedtime tended to be a negative experience, associated with depressive or anxiety-driven response. Overall, procrastination was associated with personality traits that included higher neuroticism and lower conscientiousness and extraversion.

“It could be that there are some folks who are delaying their bedtime to distract themselves from racing thoughts or worries or things like that that might be keeping them up,” Carlson said. The pattern hints at a vicious cycle: Anxiety keeps students awake; insufficient sleep magnifies anxiety. Breaking the loop often requires more than willpower, Carlson noted, it calls for structural changes or professional guidance.

For teens and adults, Carlson said, it’s ideal to have the same bedtime and wake time every day, even weekends. He recommended using an alarm to let you know when it’s time to turn off your screen and get ready for bed. For those struggling to fall asleep, body scan and meditation practices can help. But if those things don’t help, he said it’s important to turn to a behavioral sleep medicine practitioner or specialist.

Adolescence, Mirchandaney said, is “tumultuous developmental period and characterized by all of these different changes, pretty much in every aspect of life.” Sometimes, young people need professional help in what can be a tough transition to adulthood.