The Effect of Sleep on Adolescent Cognitive Function

By: Sunshine Li ‘26
I did not get enough sleep last year. On a regular night, I got around six hours of solid snooze time; add an hour to that, and Fourth Form Sunshine would consider it a good night. Eight hours would’ve been a super good night – I could count the total number of those on two hands. Occasionally, perhaps once every two weeks, I would wake up groggy from just four or five hours of shut-eye, then catch another minute as I brushed my teeth and a few more during Block 6 math. The Center for Disease Control says that about 7 out of 10 high school students don’t sleep enough during the school week. Unfortunately, myself and many others were part of that statistic. Parents tell kids to go to bed early, and everyone knows that sleep is important, but apart from avoiding drowsiness during the day, how important is getting enough sleep for teenagers, and how bad can it be if I don’t?
The effect of sleep on adolescent cognitive function has been studied widely, and the consensus is clear: sleep is incredibly important for teenagers. During adolescence, circadian rhythms shift a couple of hours later; hence, our bodies are naturally inclined to sleep later and wake up later. This is a phenomenon called delayed phase preference. However, just because adolescents feel as if we can stay up later doesn’t mean our bodies require less sleep. In fact, teens need even more sleep than 10-year-olds: Johns Hopkins pediatrician Michael Crocetti says that, ideally, we should get 9 to 9½ hours of sleep per 24 hours, since “‘teenagers are going through a second developmental stage of cognitive maturation,’” and this extra hour of sleep can help the brain thrive.
In the late 1990s, the Minneapolis public school district pushed back school start times by 1 hour and 25 minutes, changing it from 7:15 am to 8:40 am. By the year 2000, they found that attendance rates had improved, especially among high school freshmen, and that students slept around five more hours per week than they had before the change in school start time. While public high schools in America start at an average time of 8:00 am, Westminster beats that by 20 minutes – and you can be sure we are using those 20 minutes to the fullest.
I experienced the detrimental effects of sleep deprivation first-hand last year, living in a constant state of exhaustion and often acting more like a zombie than a human. The Sleep Research Society conducted a study adequately named “Need for Sleep” that showed similar results to my experience. Researchers restricted adolescent participants’ sleep to only 5 hours per night for 7 consecutive nights to “investigate the effects of sleep restriction on cognitive performance, subjective sleepiness, and mood in adolescents.” Randomly allocated to either the sleep restriction (SR) or control groups, 56 healthy teenagers underwent a variety of cognitive tests. Throughout the manipulation period, the SR group showed a progressive decline in positive mood, a rise in subjective tiredness, and a decline in sustained attention, working memory, and overall function. What I found surprising is that even after two recovery nights with 9 hours of sleep per night, the SR groups’ measurements on those aspects had not returned to baseline levels. The study establishes a negative correlation between partial sleep deprivation and cognitive function–the more sleep-deprived a student is, the worse their cognitive functions will be. Upon reading these results, I really reconsidered my self-proclaimed ability to catch up on a week’s worth of lost sleep in a single Saturday snooze.
At the end of the day, it’s night. And, at night, we should be dreaming about fluffy sheep and cotton candy instead of cramming in a last-minute test review as the wheels in our brains rust by the second. Last year’s sleep schedule was rough to say the least, but I’m proud to say that, for Fifth Form Sunshine, eight hours is a regular night, just as it should be.
Works Cited
Kirby, Matthew, Stefania Maggi, and Amedeo D’Angiulli. “School Start Times and the Sleep-Wake Cycle of Adolescents: A Review and Critical Evaluation of Available Evidence.” Educational Researcher 40, no. 2 (2011): 56–61. http://www.jstor.org/stable/41058203. 
Lo, June C., Ju Lynn Ong, Ruth L.F. Leong, Joshua J. Gooley, and Michael W.L. Chee. “Cognitive Performance, Sleepiness, and Mood in Partially Sleep Deprived Adolescents: The Need for Sleep Study.” Sleep 39, no. 3 (March 1, 2016): 687–98. https://doi.org/10.5665/sleep.5552.  
“Sleep in Middle and High School Students.” Centers for Disease Control and Prevention, September 10, 2020. https://www.cdc.gov/healthyschools/features/students-sleep.htm#:~:text=How%20much%20sleep%20someone%20needs,10%20hours%20per%2024%20hours.  
“Start Time for U.S. Public High Schools.” U.S. Department of Education NCES, February 2020. https://nces.ed.gov/pubs2020/2020006/index.asp#:~:text=While%20the%20average%20start%20time,8%3A15%20a.m.%2C%20respectively.  
“Teenagers and Sleep: How Much Sleep Is Enough?” Johns Hopkins Medicine, March 25, 2022. https://www.hopkinsmedicine.org/health/wellness-and-prevention/teenagers-and-sleep-how-much-sleep-is-enough.