8 ms·

How the brain's activity, energy use and blood flow change as people fall asleep

179 points by XzetaU8 1y ago

pedalpete 1y ago
Interesting study, but it mostly reinforces what we already know about sleep mechanics. Of particular importance is how sensory regions remain metabolically active while higher-order regions downshift during NREM sleep. That suggests the benefit of sleep depends less on how long we sleep and more on the specific activation and de-activation of networks during sleep. I work in neurotech/sleeptech as the founder of https://affectablesleep.com https://affectablesleep.com. Our stimulation triggers sensory pathways during sleep to enhance the brain’s restorative function without changing sleep time. This systematic review [1] covers non‐invasive approaches to enhancing slow‐wave activity in sleep and outlines their physiology and effects. This focused paper [2] explores the neurophysiology of closed‐loop auditory stimulation during sleep. Though the title of the post suggests the study looks at falling asleep, the study is really focused on what happens during NREM sleep, which has been our focus for the last few years. Of particular interest to me right now are the processes of waking. Research suggests that different neural networks come online in a specific sequence, and when that sequence is disrupted, we experience sleep inertia or the sense of not being fully restored. [1]https://doi.org/10.1016/j.smrv.2021.101438 https://doi.org/10.1016/j.smrv.2021.101438 [2]https://doi.org/10.1111/ejn.16132 https://doi.org/10.1111/ejn.16132
Lucian6 1y ago
[dead]
Rileyen 1y ago
I used to think sleep was just like shutting off a computer. But after one night of insomnia, my brain felt foggy all day and I could barely speak clearly. That made me realize sleep is not just about resting the body. I have been trying deep breathing before bed and it seems to help a little.
jansan 1y ago
Only slightly related, but I often try to find ways to fall asleep faster. One thing that seems to work in some situations is trying to imagine a void (like a white or gray plane) for a while. However, often enough this does not work and I wonder if anyone knows of tricks that work for her/him (without using Melantonin or other drugs).
- CrimsonCape 1y ago
  I have a routine and the crazy part is that it is 100% effective, in that I can be restless, consciously start the routine, and 100% of the time I fall asleep. It is the oddest feeling to begin the routine, which requires conscious mental effort, and suddenly you can't remember anything because you fell asleep. I can only ever recall doing it at times when my mind is racing, so I can't say how well it works when calm as I forget to do the routine when calm. The routine is basically a game to see if you can "flow" between mental images by envisioning scenes in your mind and then allowing some object in the scene to "pull" you into a different scene. For example, envision the power cable of your lamp, you fly along the power cable up to the light bulb, and then you envision the bulb glass exploding into a million pieces, which becomes snow falling on a ski lodge, you see the warm glow of fire in the fireplace, and a fireball blasts out the chimney into the sky, somehow becomes a perfect flaming sphere, that becomes a meatball and falls into a plate of spaghetti, you are eating it down, you see yourself at a ratty diner table, under the table you see your shoes, and then your shoes are running through rain puddles, you zoom into a single droplet which is actually a massive aquarium tank, fish are swimming in it except we are in the ocean, not a tank, and the fish is so colorful but those colors are actually an explosion of rainbow paint colors dripping down an apartment wall, etc. etc. It might sound ridiculous when written in words, but that is the gist of it. The game is to lay there and consciously morph and fly between mental images, letting your mind conjure imagery that comes next. It's crazy because I start doing this with a conscious struggle to envision the next chain-of-events but suddenly my brain catches on and starts unconsciously playing the game and images just kinda flow and BAM asleep.
- cube2222 1y ago
  Box breathing (2 secs in, 2 secs hold, 2 secs out, 2 secs hold) or meditation both usually help if I can’t fall asleep. Physical exercise during the day also helps.
anpwellness 1y ago
[dead]
shevy-java 1y ago
If that damn beast would ever fall asleep! Still listening to "Insomnia" from Faithless.
- hshdhdhehd 1y ago
  Tearing off tights with my teeth
submeta 1y ago
Tangential: Have had sleep disorders my whole life. Until I read an article here about melatonin (an article that was about substances that have an effect on longevity). So I started taking melatonin every night, 0.5mg. I must say: Never had this kind of deep sleep. Over such a long period of weeks (since I started taking it). My Garmin watch has a sleep tracker. And it confirms that I get way more deep sleep.
- v7engine 1y ago
  I am considering taking melatonin supplements. Could you recommend any? I wake up several times in the night.
  - submeta 1y ago
    I am in Germany, so I cannot recommend any. Just one without any supplements, just melatonin.
    - plumeria 1y ago
      I wish dm stores were available internationally
  - warp 1y ago
    My understanding is that melatonin helps you fall asleep, but doesn't help you stay asleep. In general, I have no trouble falling asleep, but I typically wake up once or twice at night and am usually unable to sleep more than 5.5 hours. I've tried 3mg Melatonin tablets in Ecuador, and I've tried a couple of different brands of 10mg time-release Melatonin gummies from the US. None of them had any noticeable effect on me. The only thing that has worked so far, is physical activity. We just moved to Europe, and the first two weeks was a lot of buying and building furniture, slept great those two weeks. Now that I'm back to my normal office worker life, my sleep has also gone back to not being great. (I track my sleep using the AutoSleep app on iOS, wearing an Apple Watch at night)
    - dpeckett 1y ago
webnrrd2k 1y ago
Taking melatonin has been mentioned several times in different threads here, and I just wanted to add my experience... I find that taking the minimal amount make a big difference here, and it's about 3 micro-grams (not milli-grams) for me. The trick is to get some liquid melatonin drops. There is a brand that has 3 milligrams per 30 drops as a recommended dosage, so I just take 3 or so drops and let them dissolve on my tongue. Using liquid drops this way, there is less of a sleep hangover, and It workes faster that way, too. I think I read about 3 micrograms as more appropriate for most people on lesswrong, but it might have been somewhere else. It's working really well for me, with frequent breaks from it, for five or more years.
- jonahrd 1y ago
  That would be 300 micrograms
- mallomarmeasle 1y ago
  As pointed out above me, 250-300 micrograms is what you likely meant. You might have to hunt for such low doses. I split a 1 mg tab in quarters. Repeated studies have shown that there is not an increase in efficacy, but there is an increase in adverse effects when doses are higher. See https://slatestarcodex.com/2018/07/10/melatonin-much-more-than-you-wanted-to-know/ https://slatestarcodex.com/2018/07/10/melatonin-much-more-th...
  - wahnfrieden 1y ago
    Products exist in US and recently Canada too
- hypeatei 1y ago
  What time do you take them? An hour before going to sleep or right before?
  - AngryData 1y ago
    Not the same guy but, when I took them it was as I was laying down to try to sleep, so maybe 10 minutes before I was actually asleep. In my experience you don't want to take them and not try to go to sleep right afterwards or you can ruin the effect, and trying to take more trying to sleep afterwards merely results in addiction and needing it to sleep at all. I can also confirm you want a very low dosage. Higher dosages didn't help at all, just merely built tolerance to it. The ones I got were 3-5mg and I broke them up into tiny little pieces and took partial mgs at most. You want to nudge yourself towards sleep with it, not try to drug yourself with it.
dpeckett 1y ago
I'm pretty sure at this point I have familial advanced sleep phase syndrome of an unknown genetic etiology [1]. Wake up stupid early in the morning, get drowsy very early in the evenings etc. For a long time due to social pressure/habit I'd just power through the evening drowsiness. That lead to me only being able to sleep six hours or so (due to waking up stupid early), which over time lead to a substantial sleep debt. Going to bed early helps a lot, but over time it seems like I easily start drifting earlier and earlier. I've recently had some success stabilizing my rhythm using sublingual melatonin when I first waken at 2-3am. Let's me get a couple extra hours of additional quality sleep which is a lifesaver. Wears off quick enough that by 9am or so it's basically out of my system. I've actually been tinkering/hacking the last year or so on sleep tracking wearables. Initially focused on EEG/HRV monitoring but I'm taking a very modular approach and ultimately want to build a full set of sensors/effectors/etc. I've recently been experimenting a lot with skin temperature gradients, turns out in the lead up to sleep it's not just blood flow in the brain that is altered [2]. 1. https://en.wikipedia.org/wiki/Advanced_sleep_phase_disorder#Familial_advanced_sleep_phase_syndrome https://en.wikipedia.org/wiki/Advanced_sleep_phase_disorder#... 2. https://journals.physiology.org/doi/pdf/10.1152/ajpregu.2000.278.3.R741 https://journals.physiology.org/doi/pdf/10.1152/ajpregu.2000...
- soulofmischief 1y ago
  You might know this, but sleep debt doesn't just keep piling on. Eventually, and rather quickly, you may begin to experience permanent brain damage after a few nights of sleep deprivation. https://www.ahajournals.org/doi/10.1161/STR.0000000000000453 https://www.ahajournals.org/doi/10.1161/STR.0000000000000453 From one insomniac to another... In the past I've been lucky if I get 3 hours total of sleep in a night due to physical pain disorders. I have deep trouble getting into NREM. I lucid dream often and my brain is active even when I'm supposed to be sleeping. In my dreams, I have to be careful not to be too energetic or overstimulated, or I will wake up. I've had insomnia and night terrors since before I was regularly forming memories. An abusive childhood intensified that. I'm in my early 30s now and the damage is clear, both physically and to my life in general. As much as I fear them, sleeping medication seems like the only way to save myself from early onset dementia or not accomplishing certain goals due to a perpetually low energy budget. It also has prevented me from losing weight. Sleep studies have shown that people who get frequently woken up while sleeping can burn around 50% less fat.. In my case, that's my entire calorie deficit which means in order to lose weight I have to basically starve myself. Melatonin, etc. have never worked for me. All this to say... Don't wait for the damage to build up even more. Sleeping medication might change your life. I'm hoping it restores mine.
thunderbong 1y ago
Melatonin has helped, of course. But a few other steps I had read on a Reddit thread [0] also helped me - specifically the point about relaxing facial muscles. For some reason, doing this also seems to calm the mind and reduce random thoughts. [0]: https://old.reddit.com/r/sleep/comments/1bn2emp/how_do_yall_fall_asleep_almost_instantly/kwgbhjp/ https://old.reddit.com/r/sleep/comments/1bn2emp/how_do_yall_...
- Noumenon72 1y ago
  It is crazy how you can relax your face 4-5 times in a row getting less tense each time, and how well this method works to get you to sleep, especially after it has worked for a while so your body associates the relaxing with sleeping.
- buzzardbait 1y ago
  I find that Yoga Nidra helps a lot. It relaxes all your muscles and also has nothing to do with "yoga".
iandanforth 1y ago
23 healthy adults ... who were able to fall asleep inside an MRI with EEG leads stuck to their heads. That's not an easy feat!
- ASalazarMX 1y ago
  TBH the inside of an MRI is one of the most boring places in the world.
buzzardbait 1y ago
I wonder how much of sleep research is affected by the difference in sleep quality between your own bed and a lab. Even if you're on vacation and the hotel bed is of exceptional quality, your brain knows that it's in a different environment and would naturally be on partial alert, at least for the first couple of nights. Now imagine sleeping in a lab setting, knowing that your sleep data is being measured. Intellectually you know that you're not at any risk but there must be some difference in the architecture of your sleep.
- elisaado 1y ago
  I have been thinking about this too, not just for the bed but also measuring equipment like pulse-oxymeters you would wear during a study.
sys32768 1y ago
I started intermittent fasting and my sleep improved remarkably when I stopped eating calories after 3PM. Last night it shows I was awake for 16 minutes but in the morning my dream memories seem to be vast. My mother got Alzheimer's in her early 60s and was always a super light sleeper despite a healthy and happy lifestyle. I suspect her brain's glymphatic system wasn't kicking in often enough to clean her brain.
tartoran 1y ago
During my 20s I developed a severe insomnia, probably due to not knowing how to handle stress. It was so bad that I had to go to the ER because I haven't had any sleep in days and didn't know what else to do. They gave me ambien and it helped at the time, but I knew that it was not something to take long term. I then started to experiment with various methods to help me fall asleep and sleep hygene such as hot/cold showers, warm baths, relaxing exercises and meditation, lowering the room temperature, removing sources of light (especially those blue LEDs). In my 40s now and am happy to report that I no longer have any insomniac episodes and I rarely have a hard time falling asleep. Out of all the techniques I found that forcefully yawning for a couple of minutes is the most efficent way for me to induce sleep.
- maksimur 1y ago
  Would be interesting to know why yawning induces sleep at all.
  - neetle 1y ago
    My psych pointed out that yawning is a tension release mechanism, so it’s likely just punting a bunch of cortisol from your nervous system
    - mirekrusin 1y ago
      I use forced yawning to wet my eyes when they become dry, works better than any drops.
  - dotancohen 1y ago
    I do this as well. It is probably both a symptom and an initiator of certain sleep-associated changes in the body.

179 points by XzetaU8 1y ago

Interesting study, but it mostly reinforces what we already know about sleep mechanics. Of particular importance is how sensory regions remain metabolically active while higher-order regions downshift during NREM sleep. That suggests the benefit of sleep depends less on how long we sleep and more on the specific activation and de-activation of networks during sleep. I work in neurotech/sleeptech as the founder of https://affectablesleep.com https://affectablesleep.com. Our stimulation triggers sensory pathways during sleep to enhance the brain’s restorative function without changing sleep time. This systematic review [1] covers non‐invasive approaches to enhancing slow‐wave activity in sleep and outlines their physiology and effects. This focused paper [2] explores the neurophysiology of closed‐loop auditory stimulation during sleep. Though the title of the post suggests the study looks at falling asleep, the study is really focused on what happens during NREM sleep, which has been our focus for the last few years. Of particular interest to me right now are the processes of waking. Research suggests that different neural networks come online in a specific sequence, and when that sequence is disrupted, we experience sleep inertia or the sense of not being fully restored. [1]https://doi.org/10.1016/j.smrv.2021.101438 https://doi.org/10.1016/j.smrv.2021.101438 [2]https://doi.org/10.1111/ejn.16132 https://doi.org/10.1111/ejn.16132

Lucian6 1y ago

[dead]

Rileyen 1y ago

I used to think sleep was just like shutting off a computer. But after one night of insomnia, my brain felt foggy all day and I could barely speak clearly. That made me realize sleep is not just about resting the body. I have been trying deep breathing before bed and it seems to help a little.

jansan 1y ago

Only slightly related, but I often try to find ways to fall asleep faster. One thing that seems to work in some situations is trying to imagine a void (like a white or gray plane) for a while. However, often enough this does not work and I wonder if anyone knows of tricks that work for her/him (without using Melantonin or other drugs).

CrimsonCape 1y ago
I have a routine and the crazy part is that it is 100% effective, in that I can be restless, consciously start the routine, and 100% of the time I fall asleep. It is the oddest feeling to begin the routine, which requires conscious mental effort, and suddenly you can't remember anything because you fell asleep. I can only ever recall doing it at times when my mind is racing, so I can't say how well it works when calm as I forget to do the routine when calm. The routine is basically a game to see if you can "flow" between mental images by envisioning scenes in your mind and then allowing some object in the scene to "pull" you into a different scene. For example, envision the power cable of your lamp, you fly along the power cable up to the light bulb, and then you envision the bulb glass exploding into a million pieces, which becomes snow falling on a ski lodge, you see the warm glow of fire in the fireplace, and a fireball blasts out the chimney into the sky, somehow becomes a perfect flaming sphere, that becomes a meatball and falls into a plate of spaghetti, you are eating it down, you see yourself at a ratty diner table, under the table you see your shoes, and then your shoes are running through rain puddles, you zoom into a single droplet which is actually a massive aquarium tank, fish are swimming in it except we are in the ocean, not a tank, and the fish is so colorful but those colors are actually an explosion of rainbow paint colors dripping down an apartment wall, etc. etc. It might sound ridiculous when written in words, but that is the gist of it. The game is to lay there and consciously morph and fly between mental images, letting your mind conjure imagery that comes next. It's crazy because I start doing this with a conscious struggle to envision the next chain-of-events but suddenly my brain catches on and starts unconsciously playing the game and images just kinda flow and BAM asleep.
cube2222 1y ago
Box breathing (2 secs in, 2 secs hold, 2 secs out, 2 secs hold) or meditation both usually help if I can’t fall asleep. Physical exercise during the day also helps.

anpwellness 1y ago

[dead]

shevy-java 1y ago

If that damn beast would ever fall asleep! Still listening to "Insomnia" from Faithless.

hshdhdhehd 1y ago
Tearing off tights with my teeth

submeta 1y ago

Tangential: Have had sleep disorders my whole life. Until I read an article here about melatonin (an article that was about substances that have an effect on longevity). So I started taking melatonin every night, 0.5mg. I must say: Never had this kind of deep sleep. Over such a long period of weeks (since I started taking it). My Garmin watch has a sleep tracker. And it confirms that I get way more deep sleep.

v7engine 1y ago
I am considering taking melatonin supplements. Could you recommend any? I wake up several times in the night.
- submeta 1y ago
  I am in Germany, so I cannot recommend any. Just one without any supplements, just melatonin.
  - plumeria 1y ago
    I wish dm stores were available internationally
- warp 1y ago
  My understanding is that melatonin helps you fall asleep, but doesn't help you stay asleep. In general, I have no trouble falling asleep, but I typically wake up once or twice at night and am usually unable to sleep more than 5.5 hours. I've tried 3mg Melatonin tablets in Ecuador, and I've tried a couple of different brands of 10mg time-release Melatonin gummies from the US. None of them had any noticeable effect on me. The only thing that has worked so far, is physical activity. We just moved to Europe, and the first two weeks was a lot of buying and building furniture, slept great those two weeks. Now that I'm back to my normal office worker life, my sleep has also gone back to not being great. (I track my sleep using the AutoSleep app on iOS, wearing an Apple Watch at night)
  - dpeckett 1y ago

webnrrd2k 1y ago

Taking melatonin has been mentioned several times in different threads here, and I just wanted to add my experience... I find that taking the minimal amount make a big difference here, and it's about 3 micro-grams (not milli-grams) for me. The trick is to get some liquid melatonin drops. There is a brand that has 3 milligrams per 30 drops as a recommended dosage, so I just take 3 or so drops and let them dissolve on my tongue. Using liquid drops this way, there is less of a sleep hangover, and It workes faster that way, too. I think I read about 3 micrograms as more appropriate for most people on lesswrong, but it might have been somewhere else. It's working really well for me, with frequent breaks from it, for five or more years.

jonahrd 1y ago
That would be 300 micrograms
mallomarmeasle 1y ago
As pointed out above me, 250-300 micrograms is what you likely meant. You might have to hunt for such low doses. I split a 1 mg tab in quarters. Repeated studies have shown that there is not an increase in efficacy, but there is an increase in adverse effects when doses are higher. See https://slatestarcodex.com/2018/07/10/melatonin-much-more-than-you-wanted-to-know/ https://slatestarcodex.com/2018/07/10/melatonin-much-more-th...
- wahnfrieden 1y ago
  Products exist in US and recently Canada too
hypeatei 1y ago
What time do you take them? An hour before going to sleep or right before?
- AngryData 1y ago
  Not the same guy but, when I took them it was as I was laying down to try to sleep, so maybe 10 minutes before I was actually asleep. In my experience you don't want to take them and not try to go to sleep right afterwards or you can ruin the effect, and trying to take more trying to sleep afterwards merely results in addiction and needing it to sleep at all. I can also confirm you want a very low dosage. Higher dosages didn't help at all, just merely built tolerance to it. The ones I got were 3-5mg and I broke them up into tiny little pieces and took partial mgs at most. You want to nudge yourself towards sleep with it, not try to drug yourself with it.

dpeckett 1y ago

I'm pretty sure at this point I have familial advanced sleep phase syndrome of an unknown genetic etiology [1]. Wake up stupid early in the morning, get drowsy very early in the evenings etc. For a long time due to social pressure/habit I'd just power through the evening drowsiness. That lead to me only being able to sleep six hours or so (due to waking up stupid early), which over time lead to a substantial sleep debt. Going to bed early helps a lot, but over time it seems like I easily start drifting earlier and earlier. I've recently had some success stabilizing my rhythm using sublingual melatonin when I first waken at 2-3am. Let's me get a couple extra hours of additional quality sleep which is a lifesaver. Wears off quick enough that by 9am or so it's basically out of my system. I've actually been tinkering/hacking the last year or so on sleep tracking wearables. Initially focused on EEG/HRV monitoring but I'm taking a very modular approach and ultimately want to build a full set of sensors/effectors/etc. I've recently been experimenting a lot with skin temperature gradients, turns out in the lead up to sleep it's not just blood flow in the brain that is altered [2]. 1. https://en.wikipedia.org/wiki/Advanced_sleep_phase_disorder#Familial_advanced_sleep_phase_syndrome https://en.wikipedia.org/wiki/Advanced_sleep_phase_disorder#... 2. https://journals.physiology.org/doi/pdf/10.1152/ajpregu.2000.278.3.R741 https://journals.physiology.org/doi/pdf/10.1152/ajpregu.2000...

soulofmischief 1y ago
You might know this, but sleep debt doesn't just keep piling on. Eventually, and rather quickly, you may begin to experience permanent brain damage after a few nights of sleep deprivation. https://www.ahajournals.org/doi/10.1161/STR.0000000000000453 https://www.ahajournals.org/doi/10.1161/STR.0000000000000453 From one insomniac to another... In the past I've been lucky if I get 3 hours total of sleep in a night due to physical pain disorders. I have deep trouble getting into NREM. I lucid dream often and my brain is active even when I'm supposed to be sleeping. In my dreams, I have to be careful not to be too energetic or overstimulated, or I will wake up. I've had insomnia and night terrors since before I was regularly forming memories. An abusive childhood intensified that. I'm in my early 30s now and the damage is clear, both physically and to my life in general. As much as I fear them, sleeping medication seems like the only way to save myself from early onset dementia or not accomplishing certain goals due to a perpetually low energy budget. It also has prevented me from losing weight. Sleep studies have shown that people who get frequently woken up while sleeping can burn around 50% less fat.. In my case, that's my entire calorie deficit which means in order to lose weight I have to basically starve myself. Melatonin, etc. have never worked for me. All this to say... Don't wait for the damage to build up even more. Sleeping medication might change your life. I'm hoping it restores mine.

thunderbong 1y ago

Melatonin has helped, of course. But a few other steps I had read on a Reddit thread [0] also helped me - specifically the point about relaxing facial muscles. For some reason, doing this also seems to calm the mind and reduce random thoughts. [0]: https://old.reddit.com/r/sleep/comments/1bn2emp/how_do_yall_fall_asleep_almost_instantly/kwgbhjp/ https://old.reddit.com/r/sleep/comments/1bn2emp/how_do_yall_...

Noumenon72 1y ago
It is crazy how you can relax your face 4-5 times in a row getting less tense each time, and how well this method works to get you to sleep, especially after it has worked for a while so your body associates the relaxing with sleeping.
buzzardbait 1y ago
I find that Yoga Nidra helps a lot. It relaxes all your muscles and also has nothing to do with "yoga".

iandanforth 1y ago

23 healthy adults ... who were able to fall asleep inside an MRI with EEG leads stuck to their heads. That's not an easy feat!

ASalazarMX 1y ago
TBH the inside of an MRI is one of the most boring places in the world.

buzzardbait 1y ago

I wonder how much of sleep research is affected by the difference in sleep quality between your own bed and a lab. Even if you're on vacation and the hotel bed is of exceptional quality, your brain knows that it's in a different environment and would naturally be on partial alert, at least for the first couple of nights. Now imagine sleeping in a lab setting, knowing that your sleep data is being measured. Intellectually you know that you're not at any risk but there must be some difference in the architecture of your sleep.

elisaado 1y ago
I have been thinking about this too, not just for the bed but also measuring equipment like pulse-oxymeters you would wear during a study.

sys32768 1y ago

I started intermittent fasting and my sleep improved remarkably when I stopped eating calories after 3PM. Last night it shows I was awake for 16 minutes but in the morning my dream memories seem to be vast. My mother got Alzheimer's in her early 60s and was always a super light sleeper despite a healthy and happy lifestyle. I suspect her brain's glymphatic system wasn't kicking in often enough to clean her brain.

tartoran 1y ago

During my 20s I developed a severe insomnia, probably due to not knowing how to handle stress. It was so bad that I had to go to the ER because I haven't had any sleep in days and didn't know what else to do. They gave me ambien and it helped at the time, but I knew that it was not something to take long term. I then started to experiment with various methods to help me fall asleep and sleep hygene such as hot/cold showers, warm baths, relaxing exercises and meditation, lowering the room temperature, removing sources of light (especially those blue LEDs). In my 40s now and am happy to report that I no longer have any insomniac episodes and I rarely have a hard time falling asleep. Out of all the techniques I found that forcefully yawning for a couple of minutes is the most efficent way for me to induce sleep.

maksimur 1y ago
Would be interesting to know why yawning induces sleep at all.
- neetle 1y ago
  My psych pointed out that yawning is a tension release mechanism, so it’s likely just punting a bunch of cortisol from your nervous system
  - mirekrusin 1y ago
    I use forced yawning to wet my eyes when they become dry, works better than any drops.
- dotancohen 1y ago
  I do this as well. It is probably both a symptom and an initiator of certain sleep-associated changes in the body.