When there is natural light, we wake up, and at night we feel drowsy.

當有自然光時，我們會醒來，而在夜晚，我們會感到昏昏欲睡。

This phenomenon is called the body's day and night cycle, or the circadian rhythm.

這種現象被稱為人體的晝夜週期或晝夜節律。

Circadian rhythms control how we sleep and when we wake up.

晝夜節律控制著我們的睡眠方式和醒來時間。

They are managed by the rise and fall of certain chemicals, such as the hormones melatonin and cortisol, and the neurotransmitter adenosine.

某些化學物質，如褪黑激素和皮質醇，以及神經遞質腺苷的漲落會對它們產生影響。

Melatonin, for example, is sensitive to light, increases with darkness, and helps us to settle into a deep sleep.

例如，褪黑激素對光線敏感，在黑暗中會增加，幫助我們進入深度睡眠。

Cortisol spikes in the middle of the night and causes REM sleep, the phase where we dream, and then wakes us up.

皮質醇會在半夜飆升，導致快速眼動睡眠，也就是我們做夢的階段，然後把我們喚醒。

Adenosine builds up during the day, gradually reduces our alertness, and eventually makes us feel tired.

腺苷會在白天積聚，逐漸降低我們的警覺性，最終使我們感到疲倦。

Over 24 hours, with someone sleeping from 10pm to 7am, the changes in melatonin, cortisol and adenosine typically look like this.

一個人從晚上 10 點睡到早上 7 點，在 24 小時內，褪黑激素、皮質醇和腺苷的變化通常是這樣的。

Now while people all have different circadian rhythms, known as different chronotypes, the rhythm itself shifts as we grow up and age.

雖然人的晝夜節律各不相同，被稱為不同的 "時型"，但隨著我們的成長和年齡的增長，晝夜節律本身也會發生變化。

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.

兒童出生時的晝夜節律通常較早，但進入青春期後，他們的褪黑激素和皮質醇開始發揮作用的時間較晚，是以，他們的身體對光線的反應較小，大約 2 小時後就會犯困。

They enter into what's known as a delayed sleep phase.

他們會進入所謂的延遲睡眠階段。

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.

由於大多數學校不適應這種變化，青少年最終會在工作日睡得少，而在週末睡得多，這種現象被稱為社會時差，從而導致各種問題。

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.

如果青少年缺乏休息，他們的大腦就很難集中注意力和吸收新知識，他們往往記不住白天所學的知識。

This is because sleep is essential for consolidating our experiences into our long-term memory store.

這是因為，睡眠是將我們的經驗鞏固到長期記憶存儲中的必要條件。

Teenagers naturally go through a period of lots of new sensations, and often face an identity crisis.

青少年自然會經歷一個充滿新奇感的時期，往往會面臨身份認同危機。

Now, people who sleep less naturally also have less REM sleep, the phase where we dream and that helps us regulate emotions.

現在，自然睡眠較少的人快速眼動睡眠也較少，而快速眼動睡眠是我們做夢的階段，可以幫助我們調節情緒。

Those who don't get enough of that might get extra sensitive, moody, or fail to understand their own feelings.

如果得不到足夠的營養，可能會變得格外敏感、喜怒無常，或無法理解自己的感受。

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.

缺乏休息會導致白天壓力增大，這反過來又會意味著晚上失眠，這種惡性循環會打擊天生就比較緊張的青少年。

In the best case, the stress impairs their creativity.

在最好的情況下，壓力會損害他們的創造力。

At worst, it leads to anxiety or addictions.

在最壞的情況下，它會導致焦慮或成癮。

This may be one reason why research shows that teenage suicide rates go up when a new school year starts.

這可能就是為什麼研究表明，新學年開始時青少年自殺率會上升的原因之一。

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.

睡眠還能調節影響食慾的荷爾蒙，是以當青少年晚上休息不夠時，他們往往會在白天吃得更多。

The result can be obesity or eating disorders.

其結果可能是肥胖或飲食失調。

The solution could be simple.

解決辦法可能很簡單。

Adapt social norms to biological facts and allow teenagers to sleep according to their natural circadian rhythm, and some schools have done just that.

讓社會規範適應生物事實，允許青少年按照自然晝夜節律入睡，一些學校就是這樣做的。

In the fall of 2015, Seattle Public Schools announced that it would change the school's starting time from 7.50am to 8.45am to adapt to the circadian rhythm of teenagers.

2015 年秋季，西雅圖公立學校宣佈，為了適應青少年的晝夜節律，學校將把開學時間從早上 7 點 50 分改為 8 點 45 分。

The result?

結果呢？

Pupils gained on average over 30 minutes of sleep each night.

學生平均每晚睡眠時間增加了 30 分鐘以上。

Later, they displayed higher concentration levels, reported better well-being, and increased motivation to learn.

之後，他們表現出更高的專注力、更好的幸福感和更強的學習動力。

What do you think?

你怎麼看？

Should high schools adapt to the biological rhythm of the pupils who go there?

高中是否應該適應學生的生理節奏？

How has your sleep cycle evolved and impacted your life?

您的睡眠週期是如何演變並影響您的生活的？

Tell us your thoughts and experiences in the comments below.

請在下面的評論中告訴我們您的想法和經驗。

If you like this video and want us to make more, subscribe to our channel or support us on Patreon.

如果您喜歡這段視頻並希望我們製作更多視頻，請訂閱我們的頻道或在 Patreon 上支持我們。