The teenager: maybe you have one or more of them at home? In that case, you will probably be relieved to hear that your teenager is not a lazy seven-sleeper, completely without discipline and completely without respect for meeting times, but is simply a late chronotype — which is only natural. Virtually all teens develop into late chronotypes, and it’s their natural, biological rhythm to go to bed late and get up late. You may be wondering why our circadian rhythm changes during our youth. The explanation for this shift in rhythm — that we become late chronotypes in our young years — may be found in the levels of the sex hormone testosterone. Researchers have found a link between a high level of testosterone in the body and being a late chronotype. Testosterone is a sex hormone that is primarily, in men, produced in the testicles. In women, smaller amounts of testosterone are produced in the ovaries and adrenal glands. Yet women’s testosterone levels are about six times as high as our estrogen levels — another of the female sex hormones. And women, like young men, produce increasing amounts of testosterone during puberty. During puberty, the production of testosterone becomes 100-300 times greater. Production peaks when you are a young adult, which is also the time when we are our most late chronotypes. Women are especially late chronotypes around the age of 19.5, while for young men the same applies around the age of 21.

Even in the small, isolated communities of developing countries, without electric lights and sparkling mobile screens, teenagers go to bed and get up later than their fellow citizens. Professor Till Roenneberg, in the book Das Recht auf Schlaf (2019), denies that teenagers go to bed late because they love playing computer games, sending messages to each other on whatsApp or scrolling on Instagram, Facebook and TikTok. He does this because he has studied a society without electricity — Quilombo in Brazil — and there it turns out that young people have exactly the same sleeping behavior as that which characterizes teenagers in western countries! He writes: “The same behavior that we have reported on teens and tweens in the modern world is found in communities that live without electricity and discos. These teenagers have no cell phones, no computers, no televisions, not even radios — and they still sleep well during the day unless they are woken up.” Research unequivocally shows that it is because young people must get up early for school that forces them to be awake at times when the teenage body is still optimally adjusted for needed rest. And conversely, we try to force young people to sleep, at times when they actually are ready to be up and running.

Everline Crone, a professor of cognitive neuroscience and developmental psychology, states that very few young people are able to fall asleep before 11pm. Because the majority in this age group are B-people, the vast majority are full of energy in the evening, but rather difficult to wake up in the morning. As a consequence, many will feel unwell in the first hours of school, and there may be impairment of learning and/or performance.

In the review article “Synchronizing education to adolescent biology: easy teens sleep, start school later”, it is concluded that it is a good idea to let teenagers sleep in accordance with their inner clock if you want them to thrive and make the most of school time. The researchers behind the article recommend that the meeting time for 16-year-olds should be around 10 o’clock, and for 18-year-olds it should be moved to around 11 o’clock. However, in school and secondary education, the introduction of meeting times later than 8 am is a controversial topic. It is typical that you hear from educational experts that teenagers just have to learn to go to bed earlier, and then they will automatically get up earlier as well. A former high school principal here in Denmark has stated: “The vast majority are only B-person because they go to bed too late. If they got used to going to bed at 10 pm, they could become an A-person.” One of the myths about B-people is that it’s just about getting together and getting up early. But B-persons can’t just go to bed at 10 o’clock in the evening, lie down on the pillow and fall asleep. Another argument against a later meeting time in school is that teenagers must be socialized so that they can just get used to and learn to adapt to the demands that they will later meet in society. How can we in the 21^st century maintain a meeting time at 8 o’clock in school with the argument that students should learn to get up in the morning and go to work? It made good sense to get up early in the agricultural community, but today only four percent of the population works in agriculture. The farming peasant culture is still present, deeply retained in all of us, and so from generation to generation we smash the children’s natural sleep-wake rhythm. Sadly, this has as a consequence that they can’t feel themselves later in life — because they have to get up; up and go to school. Think about what a little later meeting times could do for young people’s concentration, and furthermore for their overall health. Research shows that a later meeting time gives both more sleep and higher grades among the young people.