When children become teenagers, hormonal changes shift their circadian rhythm—they get tired later. Since schools typically don’t adapt to their new natural sleep cycle, they often get less sleep during weekdays, affecting their memory retention, emotional well-being, and health. If we want teenagers to learn and prosper, schools could do what sounds so simple, adjust their start times to the biological rhythms of their students.
the full story

As humans, we spend roughly a third of our lives asleep. When there is natural light we wake up, and at night we feel drowsy. This phenomenon is called the body’s “day and night” cycle or the circadian rhythm.
circadian rhythms

Circadian rhythms control how we sleep, and when we wake up. They are managed by the rise and fall of certain chemicals such as the hormones melatonin and cortisol, and the neurotransmitter adenosine.
hormones’ roles

Melatonin for example is sensitive to light, increases with darkness, and helps us to settle into a deep sleep. Cortisol spikes in the middle of the night and causes REM sleep – the phase where we dream — and then wakes us up. Adenosine builds up during the day, gradually reduces our alertness, and eventually makes us feel tired.
Circadian shifts

Over 24 hours: with someone sleeping from 10 pm to 7 am the changes in melatonin, cortisol, and adenosine, typically look like this.
Now while people all have different circadian rhythms, known as different chronotypes, the rhythm itself shifts as we grow up and age.
social jet lag

Children are typically born with an early circadian rhythm, but when they enter puberty, their melatonin and cortisol kick in later, and as a result their bodies react less to light and get sleepy about 2 hours later. They enter into what’s known as a delayed sleep phase.
And since most schools don’t adapt to this change, teenagers end up sleeping less during weekdays, and more during weekends — a phenomenon known as social jet lag. And this leads to all kinds of problems.
affect on teenagers

When teenagers lack rest, their minds have trouble paying attention and absorbing new knowledge, and they often cannot remember what they have learned during the day. This is because sleep is essential for consolidating our experiences into our long-term memory store.
Stress, sleep and mental health

Teenagers naturally go through a period of lots of new sensations and often face an identity crisis. Now people who sleep less, naturally also have less REM sleep — the phase where we dream, and that helps us regulate emotions. Those who don’t get enough of that might get extra sensitive, moody, or fail to understand their own feelings.

A lack of rest leads to more stress during the day, which in turn can mean insomnia at night – a vicious cycle that can hit adolescents who are naturally more tense. In the best case, the stress impairs their creativity. At worst, it leads to anxiety or addictions. This may be one reason why research shows that teenage suicide rates go up when a new school year starts.
Sleep also regulates the hormones responsible for our appetite. And so, when teenagers don’t rest enough at night, they tend to eat more during the day. The result can be obesity or eating disorders.
possible solution

The solution could be simple: adapt social norms to biological facts and allow teenagers to sleep according to their natural circadian rhythm. And some schools have done just that.
seattle schools’ success

In the fall of 2015, Seattle public schools announced that it would change the school starting time from 7:50 AM to 8:45 — to adapt to the circadian rhythm of teenagers. The result: pupils gained on average over 30 minutes of sleep each night. Later they displayed higher concentration levels, reported better wellbeing, and increased motivation to learn.
what do you think?

What do you think? Should high schools adapt to the biological rhythm of the pupils who go there? How has your sleep cycle evolved and impacted your life? Tell us your thoughts and experiences in the comments below!
Sources
- Circadian rhythm – Wikipedia.org
- Crowley, S. J., Cain, S. W., Burns, A. C., Acebo, C., & Carskadon, M. A. (2015). Increased Sensitivity of the Circadian System to Light in Early/Mid-Puberty. The Journal of clinical endocrinology and metabolism, 100(11), 4067–4073.
- Hagenauer, M. H., Perryman, J. I., Lee, T. M., & Carskadon, M. A. (2009). Adolescent changes in the homeostatic and circadian regulation of sleep. Developmental neuroscience, 31(4), 276–284.
- Gamble, K. L., Berry, R., Frank, S. J., & Young, M. E. (2014). Circadian clock control of endocrine factors. Nature reviews. Endocrinology, 10(8), 466–475.
- Lamon, S., Morabito, A., Arentson-Lantz, E., Knowles, O., Vincent, G. E., Condo, D., Alexander, S. E., Garnham, A., Paddon-Jones, D., & Aisbett, B. (2021). The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment. Physiological reports, 9(1), e14660.
- Dunster, G. P., de la Iglesia, L., Ben-Hamo, M., Nave, C., Fleischer, J. G., Panda, S., & de la Iglesia, H. O. (2018). Sleepmore in Seattle: Later school start times are associated with more sleep and better performance in high school students. Science advances, 4(12), eaau6200.
- Urton, J. (2018, December 12). Teens get more sleep, show improved grades and attendance with later school start time, researchers find. UW News.
- Genzel, L., Kroes, M. C., Dresler, M., & Battaglia, F. P. (2014). Light sleep versus slow wave sleep in memory consolidation: a question of global versus local processes?. Trends in neurosciences, 37(1), 10–19.
- SciPos. (2022, June 25). Grad Publication: Gideon Dunster on the benefits of delayed school start for Seattle high-school students . Science Positive – The latest on the happenings in the Biology department at the University of Washington.
Dig deeper!
- Read this paper showing that clock genes that regulate circadian rhythm also influence memory functions
- Read this paper that indicates that schools with start times before 8:30 a.m. had 10–11% higher odds of students attempting suicide compared to schools with late start times, though these differences were not statistically significant.
- Read about how teenagers have changes in their circadian rhythm
- Read the full story about how Seattle schools helped teenagers get more sleep
Classroom activity
During this activity students will learn about circadian rhythms
- Ask the class who is a morning person and who isn’t.
- Separate the class into “early birds” and “night owls”
- Ask them where they think this difference comes from, and if their rhythms have shifted during their lives.
- Show them Sprouts’ video on Teenagers and Sleep
- Ask them how they feel sleep impacts their life and learning
- Ask the students what they can implement at home or school to make their lives better.
Collaborators
- Script: Ludovico Saint Amour di Chanaz and Jonas Koblin
- Artist: Pascal Gaggelli
- Voice: Matt Abbott
- Coloring: Nalin
- Editing: Peera Lertsukittipongsa
- Production: Selina Bador
- Sound Design: Miguel Ojeda