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“Sleep” is a big question for most modern people. What time should I sleep? How long do you want to sleep? What should I pay attention to before going to bed? How can we improve the quality of sleep? …Most of these problems reflect the difficulties we encounter in our lives.

Research over the past century or so has shown us how serious the physical and mental problems arising from “not getting enough sleep” are. From high blood pressure, autoimmune system disorders, memory impairment, to depression, dissociation, and even fantasy delusions and other psychological diseases have an impact, so poor sleep quality can be said to be the biggest invisible killer of modern people. Over.

Sleep quality affects physical and mental problems. Photo/Pexels

Most of us have heard the saying “At least 6 hours of sleep a day”. Other theories such as full sleep cycle and don’t interrupt the rapid eye movement (REM) period often appear in daily life. Recently, however, a group of scholars have done ultra-large-scale sleep research during the COVID-19 epidemic when everyone is at home to prevent the epidemic. They found that in addition to “how long to sleep,” and “when to start to sleep” may also have a significant impact on people’s mental health.

“Quantitative change leads to qualitative change” sleep research

In fact, “sleep” related research has always been a health issue focused on by psychology, neuroscience, and modern medicine. However, it is a pity that although many people have been deeply involved in this field, it is still difficult to arrive at an “ideal” result. In the final analysis, because the behavior of “sleeping” takes too much time, coupled with the limitation of effective tracking, it is difficult for a research team with limited funds to achieve perfection.

Sleep takes a lot of time. Picture/Giphy

Some sleep studies that focus on “quality” require subjects to enter effective sleep at a specified time and environment, and to observe their physiological changes during sleep with the assistance of professional equipment. This type of research can often produce valuable data, but they are all based on high research costs, the scale is not large, and the number of effective samples is limited.

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Most of the studies that value “quantity” ask subjects to cooperate with a prescribed sleep pattern and follow up after a period of time. The tracking method can be self-reporting questionnaires, or observing changes in the subject’s physiological state through physiological examination equipment. The advantage of this type of research method is that the number of samples is large, and the results of the analysis can reflect the actual situation; but relatively, because there is no way to intervene in the daily life of the subject, it is easy for the subject to happen due to accidental events (for example: overtime work). , Private itinerary, etc.) and “left behind.”

In addition, because mental illness can also lead to unhealthy sleep cycles, it is difficult for relevant researchers to distinguish the causal relationship between “mental illness” and “sleep” in clinical research.

In order to overcome the uncontrollability of “people”, a research team composed of universities in the United States and the United Kingdom decided to dig deeper, starting from the “gene” level that is difficult to influence from external factors. Not only researching “sleep”, the team also wants to understand the influence of “sleep time” on mood disorders “depression”.

It is difficult to distinguish causality between sleep and mental illness. Photo/Pexels

After identifying more than 340 common genetic variants, Dr. Daghlas of the Department of Medicine of Harvard University and his research team directly cooperated with the genetic testing company 23andMe in the United States and the UK Biobank to obtain nearly 850,000 anonymous gene combinations, psychiatric history and other data. Among them, 85,000 pieces of data are accompanied by sleep cycle records measured by personal wearable devices. In addition, 250,000 people have filled out sleep preference (how long do they usually sleep and how long) questionnaires.

Such a large number of samples has caused a “qualitative change” in the value of this research.Especially when comparing gene variants in the past, the number of samples was often severely diluted due to too many variants. This gathering of the power of different schools and gene databases in Europe and the United States allowed the research team to break through the limitations of previous statistical analysis and obtain results with ideal external validity.

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One hour a day, melancholy far away?

In conclusion: Even if the total number of sleep hours remains the same, just falling asleep one hour earlier each day is enough to reduce the risk of depression by 23%. If you fall asleep two hours early, the risk reduction is astonishing 40%. It is worth noting that this benefit is for night owls who often go to bed late. Whether people who go to bed early and get up early have the same effect remains to be studied.

Since this study is not an experiment, we cannot clearly distinguish the causal relationship between “falling asleep earlier” and “decreased risk of depression”. However, if we combine the results of other studies in the past, we can actually find different explanations:

From a physiological point of view, people who go to bed and get up early will have longer “sun exposure time” than night owls. In addition to vitamin D, exposure to sunlight may also affect the efficiency of our brain to produce serotonin, which in turn affects our emotional stability. In the past, European and American studies have found that depression and bipolar disorder (bipolar disorder) are all related to seasonal changes, and it is speculated that they are related to the drastically reduced sunshine time in autumn and winter.

Sun exposure is conducive to the synthesis of vitamin D. Picture/Giphy

From a social point of view, since most people still follow the sun in their daily routines, being a night owl also indirectly means that it is difficult for us to maintain a sufficient “physical” social life. The connection between people is not just a pastime, but also an extremely important safety net for mental health, which can provide us with the resilience and support we need at critical moments.

As Dr. Daghlas mentioned in the paper: “We live in a society where “work at sunrise and rest at sunset”, and night owls who go against this normal life are likely to feel out of touch with society. sense.”

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Therefore, when our lives are staggered with family and friends, this “isolation” is likely to ferment and lead to depressing “loneliness” and “lost.”

The sense of isolation between the work and rest of life and relatives and friends. Photo/Pexels

To improve sleep, you can do this

Although this study has produced exciting results, it is after all only a study that has no way to deduce causality, and a large number of clinical experiments are still needed to clarify the mechanism in the follow-up.In addition, the focus of this research discussion is on the possible benefits of “falling asleep early”, but there are still many aspects of sleep that deserve our attention.

There are countless studies on insufficient sleep and poor sleep quality, and the results obtained are very consistent, all warning us of the risks behind unhealthy work and rest. Especially due to the recent epidemic, it is easy to mess up the daily routine of going to work and class to check and balance, which makes us fall into a negative cycle of falling asleep more and more late and getting worse.

Instead of struggling with “going to bed one hour earlier”, it is better to think of a way to “sleep one more hour” or try “not using 3C products one hour before going to bed” to bring a positive change to your life.


  • Beecher, M. E., Eggett, D., Erekson, D., Rees, L. B., Bingham, J., Klundt, J., … & Boardman, R. D. (2016). Sunshine on my shoulders: weather, pollution, and emotional distress. Journal of affective disorders, 205, 234-238.
  • Daghlas I, Lane JM, Saxena R, Vetter C. Genetically Proxied Diurnal Preference, Sleep Timing, and Risk of Major Depressive Disorder. JAMA Psychiatry. Published online May 26, 2021. doi:10.1001/jamapsychiatry.2021.0959
  • University of Colorado at Boulder. (2021, May 28). Waking just one hour earlier cuts depression risk by double digits, study finds. ScienceDaily. Retrieved June 29, 2021 from
  • Sansone, R. A., & Sansone, L. A. (2013). Sunshine, serotonin, and skin: a partial explanation for seasonal patterns in psychopathology?. Innovations in clinical neuroscience, 10(7-8), 20.

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