Journal Club with Dr. Peter Attia | Effects of Light & Dark on Mental Health & Treatments for Cancer

1. 0:00 – 2:40

   Dr. Peter Attia, Journal Club

   1. AHAndrew Huberman0:00

      (instrumental music) Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today marks the second episode in our Journal Club series with myself and Dr. Peter Attia. Dr. Peter Attia, as many of you know, is a medical doctor who is a world expert in all things healthspan and lifespan. He is the author of the best-selling book Outlive as well as the host of his own terrific podcast, The Drive. For today's episode, Peter and I each select a different paper to share with you. We selected these papers because we feel they are both extremely interesting and extremely actionable. First, I present a paper that is about how light exposure during the morning and daytime as well as dark exposure at night each have independent and positive effects on mental health as well as the ability to reduce the symptoms of many different mental health disorders. Now, I've talked before on this podcast and elsewhere about the key importance of seeing morning sunlight as well as trying to be in dim light at night. However, the data presented in the paper today really expands on that by identifying the key importance of not just morning sunlight, but getting bright light in one's eyes as much as is safely possible throughout the entire day and a separate additive effect of being in as much darkness at night as possible. I describe the data in a lot of detail, although you do not need a background in biology in order to understand that discussion. And there's a key takeaway, which is that if you can't get enough light in your eyes during the daytime, you would be well-advised to get as much darkness exposure at night. In other words, light and dark have independent and additive effects on mental health, and during today's discussion, you'll learn exactly how to apply light exposure and dark exposure in order to get those benefits. Then Peter presents a paper about novel treatments for cancer. I must say, it's an extremely important conversation that everybody, regardless of whether or not you may have had cancer or know somebody who's had cancer, ought to listen to. He highlights the current technology of cancer treatments as well as the future technology of cancer treatments, and the key role that the immune system and the autoimmune system play in treatments for cancer. I assure you that by the end of today's Journal Club episode, you will have learned a ton of new information about light and dark and mental health as well as cancer and the immune system and treatments for curing cancer. Before

2. 2:40 – 7:14

   Sponsors: Eight Sleep, BetterHelp & Joovv

   1. AHAndrew Huberman2:40

      we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero-cost-to-consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Eight Sleep. Eight Sleep makes smart mattress covers with cooling, heating, and sleep tracking capacity. I've spoken many times before on this podcast about the fact that sleep is the foundation of mental health, physical health, and performance. Now, a key component of getting a great night's sleep is that in order to fall and stay deeply asleep, your body temperature actually has to drop by about one to three degrees, and in order to wake up feeling refreshed and energized, your body temperature actually has to increase by about one to three degrees. One of the best ways to make sure that those temperature changes occur at the appropriate times, at the beginning and throughout and at the end of your night when you wake up, is to control the temperature of your sleeping environment, and that's what Eight Sleep allows you to do. It allows you to program the temperature of your mattress and sleeping environment such that you fall and stay deeply asleep easily and wake up each morning feeling incredibly refreshed and energized. I've been sleeping on an Eight Sleep mattress cover for almost three years now, and it has dramatically improved the quality of my sleep, so much so that when I travel and I'm at a hotel or an Airbnb and I don't have access to my Eight Sleep, I very much look forward to getting home because my sleep is always better when I sleep on my Eight Sleep mattress cover. If you'd like to try Eight Sleep, you can go to eightsleep.com/huberman to get $150 off their Pod 3 mattress cover. Eight Sleep currently ships in the USA, Canada, UK, select countries in the EU, and Australia. Again, that's eightsleep.com/huberman. Today's episode is also brought to us by BetterHelp. BetterHelp offers professional therapy with a licensed therapist carried out online. Now, I've been going to therapy for well over 30 years. Initially, I didn't have a choice. It was a condition of being allowed to stay in school, but pretty soon I realized that therapy is extremely valuable. In fact, I consider doing regular therapy just as important as getting regular exercise, including cardiovascular exercise and resistance training, which of course I also do every week. The reason I know therapy is so valuable is that if you can find a therapist with whom you can develop a really good rapport, you not only get terrific support for some of the challenges in your life, but you also can derive tremendous insights from that therapy, insights that can allow you to better not just your emotional life and your relationship life, but of course also the relationship to yourself and to your professional life, to all sorts of career goals. In fact, I see therapy as one of the key components for meshing together all aspects of one's life and being able to really direct one's focus and attention toward what really matters. If you'd like to try BetterHelp, go to betterhelp.com/huberman to get 10% off your first month. Again, that's betterhelp.com/huberman. Today's episode is also brought to us by Joovv. Joovv makes medical-grade red light therapy devices. Now, if there's one thing I've consistently emphasized on this podcast, it's the incredible role that light can have on our biology. And of course I'm always telling people that they should get sunlight in their eyes as soon as possible after waking on as many days of their life as possible for sake of setting circadian rhythm, daytime mood, focus, and alertness, and improved sleep. Now, in addition to sunlight, red light and near-infrared light has been shown to have positive effects on improving numerous aspects of cellular and organ health, including faster muscle recovery; improved skin health and wound healing, even improvements in acne, or that is removal of acne; reducing pain and inflammation; improving mitochondrial function; and...... even improving vision itself. What sets Joovv apart and why it's my preferred red light therapy device is that it has clinically proven wavelengths, meaning it uses specific wavelengths of red light and near-infrared light in combination that trigger the optimal cell or adaptations. Personally, I use the handheld Joovv every day. The handheld Joovv is about the size of a thick piece of toast. And I also own a Joovv panel that allows for full body exposure, and I use that one approximately five times per week for about 10 to 15 minutes per session. If you'd like to try Joovv, you can go to Joovv, spelled J-O-O-V-V, .com/huberman. Again, that's joovv.com/huberman. For this month only, January 2024, Joovv is offering exclusive discounts to Huberman Lab listeners with up to $500 off select Joovv products. Again, that's Joovv, spelled J-O-O-V-V, .com/huberman to get up to $500 off select Joovv products. And now for my discussion with Dr. Peter Attia.

   2. PAPeter Attia7:13

      Andrew,

3. 7:14 – 11:16

   Light, Dark & Mental Health; Retina

   1. PAPeter Attia7:14

      great to have you here for journal club number two. I'm already confident this is going to become a regular for us.

   2. AHAndrew Huberman7:21

      I'm excited. I really enjoy this because I get to pick papers I'm really excited about. I get to hear papers that you're excited about, and we get to, um, sharpen our skills at reading and sharing data, and people listening can do that as well.

   3. PAPeter Attia7:37

      So last time I went first, so, uh, I think I'm gonna put you in the hot seat first and have, uh, have you go first and I'll follow you.

   4. AHAndrew Huberman7:44

      Okay. Well, I'm really excited about this paper, um, for a number of reasons. First of all, it, at least by my read, is a very powerful paper in the sense that it examined light exposure behavior as well as dark exposure behavior, and that's going to be an important point, in more than 85,000 people as part of this, um, cohort in the UK. Um, I'll just mention a couple of things to give people background, and I'll keep this relatively brief. First of all, there's a longstanding interest in the relationship between light and mental health and physical health, and we can throw up some very well agreed upon bullet points. First of all, there is such a thing as seasonal affective disorder. It doesn't just impact people living at really northern locations, but basically there's a correlation between day length and mood and mental health, such that for many people, not all, but for many people, when days are longer in the spring and summer, they feel better. They report fewer depressive symptoms. And conversely, when days are shorter, significantly more people report feeling lower mood and affect, okay? So there's a longstanding treatment for seasonal affective disorder, which is to give people exposure to very bright light, especially in the morning. The way that that's normally accomplished is with these SAD lamps, seasonal affective disorder lamps, and those lamps are basically bright, meaning more than 10,000 lux lights that they place on their kitchen counter or at their table in the morning or in their office, so they're getting a lot of bright light. That has proven to be fairly effective for the treatment of seasonal affective disorder. What's less understood is how light exposure in the middle of the night can negatively impact mood and health. And so where we're- we are headed with this is that there seems to be, based on the conclusions of this new study, a powerful and independent role of both daytime light exposure and nighttime dark exposure for mental health. Now a couple of other key points, the biological mechanisms for all this are really well established. There's a set of cells in the neural retina, which lines the back of your eye. They're sometimes called intrinsically photosensitive retinal ganglion cells, they're sometimes called melanopsin retinal ganglion cells. We'll talk about those in a bit of detail in a moment. It's well known that those cells are the ones that respond to two different types of light input, not one but two different types of light input, and send information to the hypothalamus where your master circadian clock resides, and then your master circadian clock sends out secretory signals, so peptides, hormones, but also neural signals to the brain and body and say, "Hey, now it's daytime, now it's nighttime. Be awake, be asleep." But it goes way beyond that. These melanopsin and intrinsically photosensitive retinal ganglion cells we know also project areas of the brain like the habenula, which can trigger negative affect, negative mood. They can trigger the release of dopamine or the suppression of dopamine, the release of serotonin, the suppression of dop- of serotonin. And so they're not just cells for setting your circadian clock. They also have a direct line, literally one synapse away, into the structures of the brain that we know powerfully control mood. So, so the mechanistic basis for all this is there. So there's just a couple

4. 11:16 – 16:17

   Outdoor vs. Indoor Light, Cataracts, Sunglasses

   1. AHAndrew Huberman11:16

      of other key points to understand for people to really be able to digest the data in this paper fully. There are basically two types of stimuli that these cells respond to. One is b- very bright light, as we just talked about. That's why getting a lot of daytime sunlight is correlated with elevated mood. That's why looking at a 10,000 lux artificial lamp can offset seasonal affective disorder.

   2. PAPeter Attia11:41

      By the way, just a couple questions on that. Um, how many lux does the sun provide on a sunny day at noon?

   3. AHAndrew Huberman11:47

      Okay, great question. So if you're out in the sun with no cloud cover or minimal cloud cover in the middle of the day at noon, chances are it's over 100,000 lux. Ch- On a really bright day could be 300,000 lux, okay? Most indoor environments, even though they might seem very bright, I like to think of y- your kind of like, uh, department store with the bright lights, believe it or not, that's probably only closer to 6,000 lux maximum, and probably more like 4,000 lux.... most brightly lit indoor environments are not that bright when it comes down to total photon energy.

   4. PAPeter Attia12:31

      Mm-hmm.

   5. AHAndrew Huberman12:31

      Now, e- here's the interesting thing. On a cloudy day, when you're outside, it can be as bright as or an average of 100,000 lux, but it won't seem that bright because you don't, quote-unquote, "see the sun," but it's also because when there's cloud cover, a lot of those long wavelengths of light, such as orange and red light, aren't coming through. However, and this is so important, the circadian clock, the suprachiasmatic nucleus, it sums photons. It's a photon-summing system. So basically, if you're outside in 8,000 lux, very overcast, UK winter day, and you're walking around, hopefully without sunglasses, because sunglasses are gonna filter a lot of those photons out, your circadian clock is summing the photons. So it's an integration mechanism. It's not triggered in a moment. And actually, the- the experiments of recording from these cells, first done by David Berson at Brown, were, you know, historic in the field of visual neuroscience. When you- shown bro- bright light on these intrinsically photosensitive cells, you could crank up the intensity of the light and the neurons would ramp up their membrane potential and then start spiking, firing action potentials, so krr, krr, krr, long trains of action potentials that have been shown to go on for hours. And so, that's the signal that's, uh, propagating into the whole brain and body. Okay, so the- the important thing to understand is this is not a quick switch. That's why I suggest on non-cloudy days, we'll call them, that people get 10 minutes or so of sunlight in their eyes in the early part of the day, another 10 minimum in the later part of the day, as much sunlight in their eyes as they safely can throughout the day. But since you're a physician, I should just, um... And you had a guest on talking about this recently. When the sun is low in the sky, low solar angle sunlight, that's really the key time for reasons we'll talk about in a moment, and when the sun is low in the sky, you run very, very little risk of inducing cataract by looking in the general direction of the sun. You should still blink as needed to protect the eyes. It's when the sun is overhead and there's all those photons coming in quickly, in one, in a short period of time, that you do have to be concerned about cataract and, um, macular degeneration if you're getting too much daytime sunlight. So the idea is sunglasses in the middle of the day are fine, but you really should avoid using them in the early and later part of the day, unless you're driving into the sun and you n- you know, for safety reasons.

   6. PAPeter Attia15:01

      A- another question, Andrew.

   7. AHAndrew Huberman15:02

      Yeah.

   8. PAPeter Attia15:02

      If- if a person is indoors, but they have large windows, so they're s- they're getting tons of sunlight into their space, they don't even need ambient indoor light, how much of the photons are making it through the glass, and how does that compare to this effect?

   9. AHAndrew Huberman15:19

      Yeah. In general, unless the light is coming directly through the window, most of the relevant wavelengths are filtered out.

   10. PAPeter Attia15:27

       In other words, if you can't see the sun through the window, even if sufficient light is being provided, that's insufficient to trigger this phenomenon?

   11. AHAndrew Huberman15:35

       That's right. However, if you have, um, you know, windows on your roof, which some people do, skylights, that makes the situation much, much better. In fact, the neurons that, in the eye, that signal to the circadian clock in these mood centers in the brain reside mainly in the bottom two-thirds of the neural retina and are responsible for looking up basically. They're gathering light from above. These cells are also very low resolution, so s- think of them as big pixels. Uh, they're not interested in patterns and edges and movement. They're interested in how much ambient light there happens to be. Now keep in mind that this mechanism is perhaps the most well-conserved mechanism in cellular organisms. So there...

5. 16:17 – 24:55

   Tools: Sunrise & Sunsets, Circadian Rhythm; Midday Light

   1. AHAndrew Huberman16:17

      And I'll use that as a way to frame up the four types of light that one needs to see every 24 hours for optimal health. And- and when I say optimal health, I really mean mental health and physical health, but we're gonna talk about mental health mainly today in this paper. There's an absolutely beautiful evolutionary story whereby single cell organisms all the way to humans, dogs, rabbits, and everything in between, have at least two cone opsins, one that responds to short wavelength light, AKA blue light, and another one that responds to longer wavelength light, orange and red. So your dogs have this, we have this, and it's a comparison mechanism in these cells of the eye, these neurons of the eye. They compare contrast between blues and orange, or sometimes blues and reds and pinks, which are also all long wavelength light. There are two times of day when the sky is enriched with blues, oranges, pinks, and reds, and that's low solar angle sunlight at sunrise and in the evening. These cells are uniquely available to trigger the existence of those wavelengths of light early in the day and in the evening, not in the middle of the day. So these cells have these two cone photopigments and they say, "How much blue light is there, how much red light is there, or orange light?" And the subtraction between those two triggers the signal for them to fire the signal off to the cir- circadian clock of the brain, and that's why I say look at low solar angle sunlight early in the day. What that does is it, what we call it is phase advances the clock. This can get a little technical and we don't wanna get too technical here, but think about pushing your kid on a swing. The period of that swing, the duration of that swing is a little bit longer than 12 hours, okay? So when you stand closer to the kid so his- your kid swings back and you give it an- a push, you're shortening the period, right? You're not allowing the swing to come all the way up. That's what happens when you look at morning sunlight. You're advancing your circadian clock. Translated to English or non-nerd speak, you're making it such that you will want to go to bed a little bit earlier and wake up a little bit earlier the next day.In the evening, when you view low solar angle sunlight, so in the aft- the afternoon-setting sun or evening-setting sun, you do the exact opposite. You're phase delaying the clock. It's the equivalent of your kid being at the very top of the s- of the arc, and so it's gone, you know, maybe 12 and a half hour, uh, 12 and, let's say 12 and a half hours is the duration of that swing, and you run up and you push them from behind and give them a little more push. That's the equivalent of making yourself stay up a little later and wake up a little later. These two signals average, so that y- your clock stays stable. You don't drift, meaning you're not waking up earlier every single day or going to sleep later every single day. This is why it's important to view low solar angle sunlight in the morning and again in the evening as often as possible, and it's done by that readout of those two photopigments. Now, midday sun, which contains its bright light, but you see it as white light, contains all of those wavelengths at equal intensity. So the middle of the day is the so-called circadian dead zone. In the middle of the day, bright light triggers the activation of the f- of the other opsin, the melanopsin, which increases mood, increases feelings of well-being, has some other consequences, but you can't shift your circadian clock by viewing the sun in the middle of the day because it's in the circadian dead zone. It's the equivalent of pushing your kid on the swing when they're at the bottom of the arc. You can get a little bit more, but not much, and in biological terms, you get nothing. So this is why looking at sunlight in the middle of the day is great, but it's not gonna help anchor your sleep-wake cycle. And if you think about it, this is incredible, right? Every organism from single cells to us has this mechanism to know when the sun is rising and when the sun is setting, and it's a color comparison mechanism, which tells us that actually color vision evolved first, not for pattern vision, not for seeing beautiful sunsets and recognizing, "That's beautiful," or paintings or things of that sort, but rather for setting the circadian clock.

   2. PAPeter Attia20:34

      Now, what if you only do one of these, Andrew? So what if you've got constant exposure to low morning light, but (clears throat) your job prevents you from doing the same in the evening or vice versa?

   3. AHAndrew Huberman20:45

      Yeah, a great question. Better to get the morning light because if, if you have to pick between low solar angle light earlier or later in the day, and keep in mind if you miss a day, no big deal. It's a slow integrative mechanism averaging across the previous two or three days, but if you miss a day, you'll want to get twice as much light in your eyes that next morning. The reason it's better to do in the morning as opposed to the evening, although both would be to do, uh, best would be to do both, excuse me, is that most people are getting some artificial light exposure in the evening anyway, and here's the diabolical thing. Your retina is very insensitive to light early in the day. You need a lot of photons to trigger this mechanism early in the day. As the day goes on, retinal sensitivity increases, and it takes very little light to shift your circadian clock late in the day. Keep in mind also that if you do see afternoon and evening sunlight, there's a beautiful study published in Scien- uh, Science Reports, uh, yes, Science Reports two years ago showing that that can partially offset the negative effects of artificial light exposure at night. I think of this as your Netflix inoculation. And the amount of melatonin suppression from nighttime light exposure is halved by viewing evening-setting sun. Now, keep in mind you don't need to see the sun cross the horizon. It can just be when it's low solar angle. So you're looking for those yellow/blue or blue/pink, blue/red contrasts, and on cloudy days, believe it or not, they're still there. Just you don't perceive as much of it coming through. So there really... So that's three things that we should all strive to do. View low solar angle sunlight early in the day, v- view solar angle sunlight later in the day, and get as much bright light in our eyes as we safely can, ideally from sunlight, throughout the day. And if you can't do that, g- perhaps invest in one of these, uh, SAD lights, although they can be a bit expensive. Uh, there are a couple companies that are starting to design sunrise simulators and evening simulators that are actually good, that actually work, um, but right now my read is that aside from one company out there, which, by the way, I have no relationship to, it's called the Tuo Light, T-U-O, and that light bulb was developed by the biologist at the University of Washington who basically discovered these color-opponent mechanisms. Um, those lights are not particularly expensive, but they're, um, they do seem to work. In fact, they, their, the study that is emerging, again unpublished data, seems to indicate that if you look at it for (laughs) more than five or six minutes, it can induce a mild euphoria. That's how powerful this contrast is. And what they did there in that light, I'll just tell you the mechanism, is they figured out that when most people look at low solar angle sunlight in the morning, they're getting 19 reversals of blue/orange per second. So when you look at this light, it looks like a, a barely flashing, uh, white light, but it's reversals of orange and blue, orange and, um, and, you know, red and blue, and it's happening very fast.

   4. PAPeter Attia23:39

      And so what does the, what does the person looking at it perceive?

   5. AHAndrew Huberman23:42

      Um, well, I've used one of these. Um, it just looks like a, a flickering light, and of course there's the, always the potential for a placebo effect, but-

   6. PAPeter Attia23:49

      Well, that's what I was gonna say. Is there a way to control for that by having something that looks the same to the user-

   7. AHAndrew Huberman23:56

      Yeah.

   8. PAPeter Attia23:56

      ... but of course is not producing the same photo effect?

   9. AHAndrew Huberman23:59

      Yeah, well, they've done that with the 10,000-lux SAD lamps, and you w- and which most people use to try and induce sunrise simulation in their home, but keep in r- in mind that sunrise is, gives you this comparison of short- and long-wavelength light. Just a bright 10,000-lux light triggers one of the opsins that, that, but it won't set your circadian clock. So most of the SAD lamps that are out there are activating only one of the mechanisms in these cells that's relevant, and not the one that's most relevant. So I'm excited about what Tuo is doing. I think that, um, and again, I have no relation to them, except I know the biologists who did the work that, that-... provide the mechanistic logic for th- that engineering. I still think, um, we're in the, like, the really, like, early days of this stuff. What should be done is to have this stuff built into your laptop, right? (laughs) It should be built into your phone, and hopefully it will be. Now,

6. 24:55 – 31:05

   Tools: Night & Light Exposure; Waking Before Sunrise

   1. AHAndrew Huberman24:55

      I mentioned this color contrast thing in sunrise and sunset. I mentioned the bright light throughout the day. But there's a fourth light stimulus that turns out to be really important, and this w- will provide the segue into the paper. It turns out that dark exposure at night, independent of light exposure during the day, is important for mental health outcomes. Now, most people think dark exposure, how do I think about that? Well, it is dark, yes.

   2. PAPeter Attia25:20

      A- absence of light exposure?

   3. AHAndrew Huberman25:20

      It's the absence of light. But what this paper really drives home is that people who make it a point to get dark exposure at night, AKA the absence of light at night, actually benefit even if they're not getting enough sunlight during the day. And this is especially true for people with certain mental health issues. So, I don't think we can overstate the value of prec- of accurately timed light exposure to the eyes in the context of mental health. I think, you know, the- there's so much data by now. I will say, however, that some people seem more resilient to these light effects than others, meaning some people, you know, also don't suffer from jet lag too much. Some people can stay up late, get a lot of bright light exposure in the middle of the night, and during the day, they've got their sunglasses on all day and they're in a great mood all the time. Other people are more susceptible to these sorts of things, and we don't know whether or not gen- polymorphisms underlie that. I personally am very sensitive to sunlight in the sense that if I don't get enough sunlight, I don't feel well after a couple of days, um, but I'm less sensitive to light exposure at night, for instance. But I think it is perhaps, this is a big statement, but is perhaps the most fundamental environmental stimulus for levels of arousal and alertness which correlate with all sorts of, you know, neuromodulator and hormone outputs. And, um, so it- none of this should come as any surprise. I will mention one last thing. There was a study published, gosh, over 10 years ago now from Chuck Zeissler's lab at Harvard Medical School, it's a phenomenal lab exploring circadian human health behavior. He's just considered a l- (laughs) no pun, a luminary in the field. But there wasn't a study that was in error where they had published in Science Magazine that light shown behind the knee could shift circadian rhythms, and that paper was retracted, um, and a lot of people don't know that it was retracted. Light exposure to the eyes is what's relevant here, and as far as we know, the color of one's eyes, like, the darkness or lightness of one's eyes bears no relevance on their sensitivity to these types of mechanisms and on and on. Yeah.

   4. PAPeter Attia27:25

      So, so one question, one comment. The question, again, is going back to the morning/evening light, and I spend a lot of time looking at those types of skies. For example, just 'cause of m- the nature of my hobbies.

   5. AHAndrew Huberman27:35

      Right.

   6. PAPeter Attia27:36

      Right? 'Cause I'm always doing archery in the morning and rucking in the afternoon, so it's not uncommon that I'm seeing both of those. How relevant is it that the sun be above the horizon? So for example, um, it begins to get light about in 30 minutes before sunrise.

   7. AHAndrew Huberman27:52

      Mm-hmm.

   8. PAPeter Attia27:52

      And then, you know, right at s- so if sun rises at 7:30, first light is 7:00, and then, you know, sort of 7:15 to 7:30 is actually quite bright. I mean, you can see-

   9. AHAndrew Huberman28:03

      Mm-hmm.

   10. PAPeter Attia28:03

       ... anything and everything, and the same is true at sunset. So does, does that 30 minutes pre- or when sun is beneath the horizon constitute part of that 10 minutes?

   11. AHAndrew Huberman28:13

       It does. I mean, in an ideal circumstance, you'd get outside and see the sunrise every day, and you'd see the sunset every day, even on cloudy days. M- some people like myself wake up before the sun comes up, in which c- and I get this question all the time. Well, in the absence of powers to make the sun rise faster, which I'm not aware anyone has, certainly not me, I think the best thing to do is simply to turn on as many bright lights as you can indoors to trigger that melanopsin mechanism if you want to be awake. If you want to stay asleep or sleepy, then keep them dim, and then get outside once the sun is starting to come out. Some people wake up after the sun has risen, right, in which case, get what you can. And some people wake up 10:00 AM or noon, in which case you can still get the bright light exposure but you won't shift your circadian clock. Now, in the evening, especially in the winter months, it's important to look west and try and get some sunlight in your eyes in the evening. If you've ever gone into the clinic, for instance, at 2:00 in the afternoon after lunch, you know, and then in the winter, and then come out and it's dark when you're walking to your car, it's a kind of eerie feeling. That sort of eerie feeling may correlate with the fact that y- you missed a signal, your, your brain is trying to orient your brain and body in time, and that's what all of this is, right? It's trying to orient in time. And again, some people are more susceptible to that than others. Some people might like that, um, feeling of, "Oh, I went in at- when it was bright and I come out when it's dark." But the vast majority of people feel better when they're getting this morning and evening sunlight exposure, and this is especially important in kids, all right? This is one of the things that, you know, this paper points out and there are good data that people are spending approximately 90% of their time indoors nowadays, n- daytime time indoors. And those indoor environments are simply not bright enough. You think, "Oh, there's all these bright lights," and some people are putting blue blockers on in the middle of the day, which is the worst thing you could possibly do. If you're gonna wear blue blockers, and I don't think they're necessary, but if you're going to wear them, you'd want to wear them at night. And in the evening, you don't need to wear blue blockers, you just simply should dim the lights and ideally have lights that are set a little bit lower in your environment, which the Scandinavians have been doing for a long time, so, you know, kill the overhead lights. And don't obsess about bright light exposure in the middle of the night. In fact, for a long time, I and some other people were saying, "Oh, you know, even just a brief flash of light in the middle of the night can, you know, quash your melatonin." That's true, but the other time in which...... you're in this, quote-unquote, "circadian dead zone" is in the middle of the night. You can't shift your circadian clock in the middle of the night. But, you know, all of this gets down to interweaving rhythms of light sensitivity, temperature, hormone output, cortisol. It... I mean, there's a whole landscape of circadian biology. This paper, um, which was published in a new journal that I'm really

7. 31:05 – 36:50

   Article #1, Light/Dark Exposure & Mental Health

   1. AHAndrew Huberman31:05

      excited about called Nature Mental Health, this journal was just launched recently, um, is entitled "Day- and night-light Exposure Are Associated With Psychiatric Disorders: An Objective Light Study In More Than 85,000 People." Now, I have to say that I think the title of this paper is terrible. Sorry folks at Nature Mental Health. Because if one just read the title, it sounds like "Day and night light exposure associated with psychiatric disorders." Right? (laughs) Right? If this were a, if this were a newspaper headline, you'd be like, "Oh, my goodness. Well, what are you supposed to do?" Right? But that's not the conclusion. The conclusion (laughs) is that getting a lot of sunlight exposure during the day and getting a lot of dark exposure at night is immensely beneficial for psychiatric health and in a number of ways. Now, I'm not one to bring up a- another paper unannounced, but I will say that this paper built off a previous study entitled "Time Spent In Outdoor Light Is Associated With Mood, Sleep, and Circadian Rhythm Related Outcomes." And that was a cross-sectional, longitudinal study in 400,000 biobank participants. So this UK Biobank is an incredibly valuable resource, and there are now multiple studies establishing that one's pattern of light exposure is extremely important. Now, the previous study in 400,000 participants basically nailed home the idea that the more time you spend outdoors, the better your- is your mood, the better is your sleep, the better is the rhythmicity of your sleep-wake cycles, and on and on. Something that I think even though people will say, "We've known that for thousands of years," needed scientific substantiation. This new study essentially looked at the relative contributions of daytime light exposure and nighttime dark exposure, and they did that on a background of, uh, looking pre- in particular at people who had major depressive disorder, generalized anxiety, PTSD, bipolar disorder. H- here's the, the basic takeaway, and I'll, I'll quote them here, and then I'll g- I'll tell you my interpretation. That... Here, I'm quoting. "Avoiding nightli- light and seeking light during the day," I love that word seeking, "may be a simple and effective non-pharmacologic means for broadly improving mental health." So that's a pretty bold statement, right? And I love that they say seeking, because it implies that people aren't reflexively getting the light exposure that they need, that this... It needs to be a practice, m- much like zone II cardio or resistance training. Okay, so what... So what do they do in this study? So basically, they gathered up 100,000 people or so. It eventually was pared down to about 86,000 participants, 'cause some just didn't qualify or didn't report their data back. They equipped them with accelerometers on their wrists, and those wrist devices also could measure ambient light. Now, that's not a perfect tool, 'cause what you'd love to do is measure ambient light at the level of the eyes. By the way, will somebody design an eyeglass frame that changes color when you've gotten sufficient light from sunlight during the day, and then ch- and then at night, is a different color, and then if you're getting too much light exposure, will go to a different color f- frame? This, uh, has to be possible so that you don't have to wonder if you got enough light during the day. And of course, if it's at the level of the eyes, then you know that's what's-

   2. PAPeter Attia34:20

      Y-

   3. AHAndrew Huberman34:20

      ... landing at the eyes.

   4. PAPeter Attia34:21

      Yeah, and it's le- I mean, that's what I was gonna ask you about that. I- i- do these wrist-based devices potentially get covered by clothing in some-

   5. AHAndrew Huberman34:28

      Yeah, turned over.

   6. PAPeter Attia34:29

      Like, y- you have your sleeves down-

   7. AHAndrew Huberman34:30

      Yeah.

   8. PAPeter Attia34:30

      ... I have my sleeves up.

   9. AHAndrew Huberman34:31

      Yeah, they had it on the outside of the sleeve, but they asked that people just keep it on their dominant hand. It's not perfect, but in some ways it's kind of nice that it's not perfect. We could turn that disadvantage into an advantage by thinking, you know, when the person is out and about, they're not often looking right at the sun. You know, if you're talking to a colleague under an overhang, for instance. So it's- it's not perfect.

   10. PAPeter Attia34:52

       It's directionally-

   11. AHAndrew Huberman34:53

       It's directionally, right.

   12. PAPeter Attia34:54

       Yeah.

   13. AHAndrew Huberman34:54

       Okay, and then they had two hypotheses, two primary hypotheses, one that greater light exposure in the day is associated with lower risk for psychiatric disorders, and two, second hypothesis, greater light exposure at night is associated with higher risk for psychiatric disorders and poorer mood. This is oh-so relevant for the way we live now, people on screens and tablets in the middle of the night. Okay, then they collected information about how much light exposure people were getting, as well as their sleep and their activity, and so on. I should mention this was done in males and females. It was a slightly older cohort than one is used to seeing, people in their 50s and 60s. They had psychiatric diagnosis information, and then they divided people into essentially two groups, but they had a lower, so a Q1 and a Q2, a lower quartile. That meant people that were getting less daytime light as opposed to the third and fourth quartile, more daytime light. They also had a nighttime light exposure evaluation, and they had people who were... When the low Q1 and Q2, so these people are getting less nighttime light versus Q3, Q4, more nighttime light. Nicely, they also looked at sleep duration, and they looked at photoperiod, meaning how long the days were for those individuals, how active they were. What, 10 hours a day, 14 hours a day? Because the more active you are, the more opportunity for light exposure you have during the day or night, for instance. Okay, so it... They had, I would say, fairly complete data sets. Then, and I'm just gonna kind of to- hit the top contour of what they did in each-

   14. PAPeter Attia36:30

       And sorry, sleep duration, sleep efficiency, et cetera-

   15. AHAndrew Huberman36:33

       Yep.

   16. PAPeter Attia36:33

       ... was determined off the accelerometer?

   17. AHAndrew Huberman36:34

       That's right, as well as self-report. Yeah. Not, not ideal, right? You'd love t- for people to be wearing a whoop band or, or, or a ring or something of that sort, but this was initiated some time ago, so, um, they either didn't have access to that technology or for whatever reason didn't select it.I'd

8. 36:50 – 38:18

   Sponsor: AG1

   1. AHAndrew Huberman36:51

      like to take a brief moment and thank one of our sponsors, and that's AG1. AG1 is a vitamin mineral probiotic drink that also contains adaptogens. I started taking AG1 way back in 2012. The reason I started taking it, and the reason I still take it every day, is that it ensures that I meet all of my quotas for vitamins and minerals, and it ensures that I get enough prebiotic and probiotic to support gut health. Now, gut health is something that over the last 10 years we realized is not just important for the health of our gut, but also for our immune system and for the production of neurotransmitters and neuromodulators, things like dopamine and serotonin. In other words, gut health is critical for proper brain functioning. Now, of course, I strive to consume healthy whole foods for the majority of my nutritional intake every single day, but there are a number of things in AG1, including specific micronutrients that are hard to get from whole foods, or at least in sufficient quantities. So AG1 allows me to get the vitamins and minerals that I need, probiotics, prebiotics, the adaptogens, and critical micronutrients. So anytime somebody asks me if they were to take just one supplement what that supplement should be, I tell them AG1 because AG1 supports so many different systems within the body that are involved in mental health, physical health, and performance. To try AG1, go to drinkag1.com/huberman and you'll get a year's supply of vitamin D3K2 and five free travel packs of AG1. Again, that's drinkag1.com/huberman.

9. 38:18 – 45:43

   Odds Ratio, Hazard Ratio

   1. AHAndrew Huberman38:19

      Then what they did is they got... They have information on who has major depressive disorder, who has PTSD, generalized anxiety, bipolar psychosis, et cetera, and then they ran three models. And you can tell me what you think about the power of these models, but, you know, as somebody who thinks about the mechanistic aspect of all of this a lot, but not somebody who's ever run this type of study, I'd be really curious. Model 1 examined the unadjusted association between day and nighttime light exposure and psychiatric outcome. So just basically asking, is there a relationship between how much light you get e- during the day and how much light you get at night and how bad your, or, your depression is or anxiety is, et cetera, looking at, you know, just a standard ratio of the probability that you have a certain symptom or set of symptoms versus you don't given a certain amount of light exposure. Model 2 adjusted for the age of the person, their sex and ethnicity, and photoperiod. So they looked at, you know, how long the days were in that given person's region of the world. And then model 3 also-

   2. PAPeter Attia39:30

      But these people were all in the UK, or were they around the world?

   3. AHAndrew Huberman39:32

      They were all in the UK-

   4. PAPeter Attia39:33

      Okay. All right.

   5. AHAndrew Huberman39:33

      ... as far as I know. And then model 3 adjusted for employment, so employed versus unemployed, which if you think about it, is pretty important. Like, you say, "Well, an unemployed person has a lot more time to control these variables, but an employed person who's doing shift work does not." Right? And they, they incorporated information about employed versus unemployed physical activity, which turns out to be very important, and then things like shift work, et cetera. And so these... Wha- wha- what we can say very safely is that the outcomes with each of these models, the results were very similar. So we don't want to discard the differences between those models entirely, but in... My read is in every figure of the paper, it doesn't seem like model 1, 2, or 3 differ from one another in terms of total outcome.

   6. PAPeter Attia40:22

      Yeah. Th- that's an unusual aspect of this paper. So, so these adjustments are very standard, right? So that's-

   7. AHAndrew Huberman40:28

      Okay.

   8. PAPeter Attia40:28

      This is a, a, a classic, uh, tool that's used in most epidemiology, um, because you don't have randomization. So once randomization is out the window, you know, you, you're... Like, so for example, the paper I'm gonna present is based on an RCT. There will be no models. It's just here are the data.

   9. AHAndrew Huberman40:43

      Right. Yeah.

   10. PAPeter Attia40:44

       And so you-

   11. AHAndrew Huberman40:44

       Here, they're asking people, "What, what do you do? Report back to us. We're gonna measure your light exposure." But no one was assigned any groups or swapped.

   12. PAPeter Attia40:51

       That's right.

   13. AHAndrew Huberman40:51

       They're, they're... The, the... Whatever cont- quote unquote controls are there, uh, they're really not there. It's just comparisons between groups.

   14. PAPeter Attia40:59

       So what is interesting to me, uh, (laughs) is that as... It's exactly as you said, and we'll make all these figures available in addition to the papers. But, um, I mean, there... It's very unusual that there's no difference between the unadjusted and the adjusted models. And as you say, there's probably two places out of, you know, 30 when you look at all the different quartile comparisons where you might creep from-

   15. AHAndrew Huberman41:27

       Mm-hmm.

   16. PAPeter Attia41:28

       ... you know, statistically significant just out of it or just into it.

   17. AHAndrew Huberman41:31

       Mm-hmm.

   18. PAPeter Attia41:32

       But yeah, you could simplify this figure too completely by just showing one of the models and you would be, you know, getting 95% of the information, which is... You know, I, I mean, I think in one way that suggests m- that there's less dependency on those variables. Of course, it still doesn't address probably the greatest question I have here, which I'm sure we'll get to at some point as, as you continue.

   19. AHAndrew Huberman42:01

       Yeah. So I'm very curious what that question is, but I'll ho- I'll ho- I'll suppress my curiosity-

   20. PAPeter Attia42:05

       (laughs)

   21. AHAndrew Huberman42:05

       ... for the moment. You know, so if we look at figure two of this paper, and I realize a lot of people are listening and, and they're not able to look at this, although we have posted the figures on the YouTube versions of this. Uh, just wanna make clear what's going on just for those that are listening. Essentially what they're looking at is what they call the odds ratio, which is the probability of something happening in one group vers- divided by the probability of something happening in another group. I guess, would it, by way of example be, you know, if you were gonna look at the odds ratio of, you know, the probability of somebody getting lung cancer if they smoke versus probability of somebody getting lung cancer if they don't smoke.

   22. PAPeter Attia42:42

       So odds ratios and hazard ratios are often confused. They're very similar and odds ratios generally refer to a lifetime exposure, whereas a hazard ratio is, um, defined over a specific period of time, but the math is still effectively the same. And, uh, using the example you gave, if you took the w-... odds ratio of, you know, death, so let's talk all-cause mortality for a smoker versus a non-smoker, and the answer were 1.78. I'm making that up, but that's directionally correct. 1.78 as an odds ratio means there's a 78% chance greater of the outcome of interest, in this case death by any cause, in the affected group, which would be the smokers. So, a odds ratio of two is 100%. An odds ratio of three is 200%, so the math is take the number, subtract one, and that's the percent.

   23. AHAndrew Huberman43:33

       You know, figure two of this paper is one of the key take-homes. They essentially look at the odds ratio of people who are in the... Let's say that, let's just look at the nighttime light exposure.

   24. PAPeter Attia43:47

       And just remind me, Andrew, 'cause, and- and everybody else watching, th- every one of these is showing second, third, fourth as your x-axis.

   25. AHAndrew Huberman43:54

       Right.

   26. PAPeter Attia43:54

       Meaning, they're all being compared to the first quartile.

   27. AHAndrew Huberman43:57

       That's right.

   28. PAPeter Attia43:57

       And the first quartile is lowest light exposure or highest light exposure?

   29. AHAndrew Huberman44:03

       That's right. Lowest.

   30. PAPeter Attia44:03

       Okay.
10. 45:43 – 51:35

    Night vs. Daylight Exposure, Mental Health Disorders

    1. AHAndrew Huberman45:43

       yeah, the way I would've done it is say, "Second quartile's low amounts of nighttime light exposure," and define what that is. You know, third quartile is more light exposure, and then fourth, maximum amount of light exposure at night. And basically what you see is that the probability of having worse major depressive symptoms linearly increases as you go from the second to third to fourth quartile. So, more nighttime light exposure, worse for you, and there's a dose response, if you will, of the effect. Now, we can march through or describe figure two pretty quickly by saying the same thing is true, now we're just talking about nighttime light exposure, for generalized anxiety disorder, so that's panel C. Bipolar disorder, although the difference between the second and third quar- quartile in bipolar disorder isn't as dramatic, once you get up to the fourth quartile, bipolar symptoms get much worse when people are getting nighttime light exposure. I really want to emphasize that point, because they go on in the discussion of this paper to re-emphasize that point several times. In fact, they say that while light exposure during the day, of course, we will go into the data, is beneficial for mental health. For people with bipolar disorder, it seems that light exposure at night is especially problematic, independent of how much sunlight they're getting during the day. So, your bipolar, um, in the person with bipolar disorder who's struggling with either a manic or a depressive episode, who's making a point to get sunlight during the day, who's also getting light exposure at night, is making their symptoms worse. And keep in mind, they, they couldn't completely control this, but this is largely independent of things like sleep duration. So, (laughs) that doesn't necessarily mean that the person's sleeping less, although in a bi- in a manic episode, presumably they are. It's independent of exercise, it's independent of a bunch of other things, because any, any logical person will hear this and say, "Okay, well, they're, they're getting more light at night because they're doing a bunch of other things." But it's largely independent of those other things. Likewise, the symptomatology of PTSD gets far worse with increasing light exposure at night. Self-harm really takes a, a leap from being fairly, I don't wanna say minimal, at the second and third quartile, so low and let's say medium, um, using some, uh, uh, taking some liberties here, but low and medium amounts of, of artificial light exposure at night, then for people who get quite a lot of nighttime light exposure, self-harm goes up, and probability of psycho- psychotic episodes goes up, or psychotic symptoms. Now, what's nice is that the, what's nice about the data is that the exact inverse is basically true for daytime light exposure. Although not across the board, we can generally say that for major depressive disorder, generalized anxiety, bipolar symptoms, there it's a little more scattered, PTSD and self-harm, the more daytime light exposure, ideally from sunlight, 'cause that's actually what's being measured in most cases, it- we can talk about how we know that, is going to approximately linearly drop the probability or the severity of these symptoms.

    2. PAPeter Attia49:00

       And we could just explain again that the odds ratios now seem to be going down, so an odds ratio of 0.7 now refers to a 30% reduction in the variable of interest here.

    3. AHAndrew Huberman49:10

       Exactly. Now, the, the psychosis, uh, panel F, which, uh, focuses on psychosis, I think is also worth mentioning.... in, in a bit more detail, th- there's a fairly dramatic reduction in psychotic symptoms as one gets more daytime light exposure, independent of nighttime light exposure. There's a well-known phenomenon called ICU psychosis, which is that people come into the hospital for a broken leg or a car accident, maybe they were getting surgery from, from Peter back when for something totally independent. They're h- they're housed in the hospital and as anyone who's ever been in a hospital as a patient or visitor knows, the light env- the lighting environment of the hospital is absolutely dreadful for health. Just dreadful. I mean, people often complain about the food in the cafeteria as being unhealthy, that's often, not always true, not always true. But the lighting environments in hospitals is absolutely counter to health.

    4. PAPeter Attia50:06

       Espe- especially, especially in the intensive care unit. Yeah.

    5. AHAndrew Huberman50:09

       Right. So th-

    6. PAPeter Attia50:10

       I, I don't... I'm, I think the, the intensive care unit at Hopkins, the main one, the, the main NICU didn't have windows.

    7. AHAndrew Huberman50:16

       People who, who go into the hospital with, with a brain injury or, or with a stroke or something, I get contacted all the time, even though I'm not a clinician, "What should I do for my kid, my parent, my..." I always say, "Get them near a window and start, to the best of your abilities, controlling their sleep-wake cycle." Now oftentimes there's, they're, you know, nurses coming in and taking blood tests and measuring pulses in the middle of the night, that's disruptive. There, there's bright light, not just blue light, that's disruptive. It's noisy, that's disruptive. ICU psychosis is when non-psychotic individuals start having psychotic episodes in the hospital because of nighttime light exposure and, in some cases, lack of daytime sunlight. We n- can say that with some degree of confidence because when those people go home, even though sometimes their symptoms for what th- brought them to the hospital in the first place get worse, their psychosis goes away. Now, (laughs) th- and it's independent of medication. So let's just be really direct. W- there is a possibility that we are all socially jet-lagged, that we are all disrupting these mood regulation symptoms, uh, systems, excuse me, by not getting enough daytime light and by getting too much nighttime light. If we wanna look at just some of the bullet points or the takeaways, and then Peter, thank you, you highlighted a few of these. But-

11. 51:35 – 59:15

    Major Depression & Light Exposure; Error Bars & Significance

    1. AHAndrew Huberman51:35

    2. PAPeter Attia51:35

       Can we just go back to this figure two for a second?

    3. AHAndrew Huberman51:36

       Oh, yeah, sure.

    4. PAPeter Attia51:37

       Because there's a handful of things that really jumped out.

    5. AHAndrew Huberman51:38

       I had a feeling Peter was gonna wanna, wanna dig into the data more.

    6. PAPeter Attia51:40

       Yeah, yeah.

    7. AHAndrew Huberman51:41

       Let's do it. Let's do it.

    8. PAPeter Attia51:41

       I just, um... And, and again, I normally wouldn't make so much hay out of this except for the fact that they're so tight, um, but the, there are a few that really stand out, um, and again, I love this figure. Um, I would have labeled it a little differently to make it completely user-friendly. But nevertheless, the increasing light at night and the impact on depression, uh, or the-

    9. AHAndrew Huberman52:04

       Panel A, yeah.

    10. PAPeter Attia52:04

        Let's, let me be really technical in what I say. And the relationship or correlation to depression is very strong. Um, the relationship to light and self-harm in the upper quartile, so when you take those 25% of people with the most nighttime light, that relationship to self-harm is interesting and completely uncoupled from the other 75%. That's interesting.

    11. AHAndrew Huberman52:27

        Oh, do, by uncoupled you mean that at the lower levels of light exposure at night you're not seeing an increase in self-harm?

    12. PAPeter Attia52:33

        Not whatsoever.

    13. AHAndrew Huberman52:33

        And then once you get to that fourth quartile...

    14. PAPeter Attia52:36

        It's a big step.

    15. AHAndrew Huberman52:36

        It's a, like, a 30% greater risk of self-harm.

    16. PAPeter Attia52:39

        That's right. Yeah, so it's totally flat, the first, second, third quartile, no different, and then fourth, big jump. Um, and then the, the, the inverse relationship, right? As light increases during the daytime you see this reduction in self-harm. Interesting. The PTSD relationship based on nighttime light and the psychosis relationship based on daytime light, those are the ones that really jumped out to me. Uh, I think anxiety relatively the, you know, less impressive here.

    17. AHAndrew Huberman53:08

        Mm-hmm, yep.

    18. PAPeter Attia53:08

        And, and bipolar disorder didn't seem as strong-

    19. AHAndrew Huberman53:12

        Right.

    20. PAPeter Attia53:12

        ... as well. So I think those, those are the big ones that, that-

    21. AHAndrew Huberman53:15

        I agree.

    22. PAPeter Attia53:15

        ... that, that jumped out to me.

    23. AHAndrew Huberman53:16

        Yeah, I agree. There's a bit, there's a bit more scatter on generalized anxiety and, and the degree of, the signifi- the degree of significant change is not, is not as robust. In other words, getting a lot of daytime light, ideally from sunlight, is not necessarily going to reduce your levels of anxiety. Getting a lot of nighttime light exposure is not increasing nighttime anxiety that much, although 20%, you know, is, is not nothing, um, for nighttime light exposure. But yeah, where... The psychosis, major, major depression, and self-harm are, are really, you know, they leap out. Actually, we, maybe we even just drill a little bit deeper on major depression. I mean, basically when you go from the second to third quartile of nighttime light exposure, so more nighttime light exposure, you basically go from no significant increase to almost, almost a 20% increase, and then as you get up to the fourth quartile, so the most nighttime light exposure, you're at about 25% increase in major-

    24. PAPeter Attia54:16

        Yeah.

    25. AHAndrew Huberman54:16

        ... depressive symptoms. No- that's no joke. Um, and you know, and I think that, I think that we, you know, if we were to, uh, I mean, and we don't have the data right here, but if we were to look at, what, standard SSRI treatment for major depression, you know, (laughs) um, people debate this th- pretty actively. But, um, light is, is a very potent stimulus and the timing of light is critical, because on the... The inverse is also true, as you get to the fourth quartile of daytime light exposure, you get about a 20% reduction in major depressive disorder.

    26. PAPeter Attia54:48

        What I like about a study like this is that it puts the error bars so easy to see on the data. And why is that interesting? Well, um, there's, there's, um, there's a, there's a belief that bigger is always better in sample size and we often talk about that through the lens of power analysis, right? So how many subjects do we need to, um, to, to reach a, a conclusion that is powered to, you know, this level?... and that's, that's true, but what I don't think gets discussed as often is th- the opposite of that, which is, what if you overpower a study? In other words, what if the power analysis says to be, uh, to, to have a level of power at 90%, you need 1,000 subjects, and you say, "Great, we're gonna do 10,000 subjects." Well, you're clearly powered for it, but you might be overpowered and people might say, "Well, why would that be a bad thing?" It could be a bad thing because it means you are very likely to reach statistical significance in things that might not be actually significant. And so one thing about this study that is just a quick back, like kind of a quick and dirty way to tell that it's probably not overpowered is that you have varying lengths of error bars. And what that tells me is that... And again, this is not like a formal statistical analysis. It's just kind of like a back of the envelope statistical analysis. If you look, for example, at self-harm in the top quartile, you actually have pretty big error bars. In fact, all the self-harm have sort of slightly bigger error bars, and yet when you look at, for example, the depression, even though the error bars aren't all the same size, they're tighter. In fact, when you look at the relationship between depression and daytime light, the error bars are really, really small. So, that just gives me confidence that there is variability in this, which paradoxically you kind of want to see, 'cause it tells me that this wasn't just done, you know... There was, I think you said 8,000 subjects were in this, and I realize-

    27. AHAndrew Huberman56:47

        80, more than 80, 86,000.

    28. PAPeter Attia56:49

        86,000-

    29. AHAndrew Huberman56:49

        Yeah.

    30. PAPeter Attia56:49

        Sorry.
12. 59:15 – 1:00:39

    Sponsor: LMNT

    1. PAPeter Attia59:15

    2. AHAndrew Huberman59:15

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13. 1:00:39 – 1:08:14

    Prescriptions; Environmental & Artificial Light; Red Lights

    1. AHAndrew Huberman1:00:39

       One thing that I hope people are taking away from this study is that, imagine you're somebody who has a very sensitive circadian mood system. Well, that would mean you need less daytime light exposure to feel good or less bad, but it also means that you might need very little light at night in order to negatively impact your mood systems. And in fact, they make this argument in the discussion as an interesting point that I think is worth mentioning. The way... Because here what I... Again, what I like about this study is that they've separated day and nighttime light-

    2. PAPeter Attia1:01:18

       Yeah.

    3. AHAndrew Huberman1:01:18

       ... exposure-It turns out that many of the drugs that are used to treat bipolar disorder reduce the sense... Are, are effective, perhaps in part because they reduce the sensitivity of the light-sensing circadian apparati. Now, that's interesting, right? I- if, if you think about this, okay, so these are drugs that can ameliorate some of the symptoms of bipolar perhaps in part by reducing the extent to which nighttime light exposure can relieve bipolar symptoms, c- excuse me, can exacerbate bipolar symptoms. Conversely, there's evidence that people who take certain antidepressants may suppress the ability for daytime light-

    4. PAPeter Attia1:01:59

       Mm.

    5. AHAndrew Huberman1:02:00

       ... to positively impact the mood systems of the brain. Now, of course, we don't want people halting their medication on the basis of that statement alone. Please don't. You know, talk to your psychiatrist. But if we know one thing for sure, it's that if you want a significant outcome and a paper as a scientist, give a drug, any drug, and look at the amount of rapid eye movement, sleep, or their circadian cycle. Pretty much any drug alters their circadian rhythm, for better or worse. But if we start to think about which medications might adjust our overall sensitivity to light, sometimes this could be a good thing. You think less sensitivity to light. Well, for people who have bipolar disorder, the amount of daytime light exposure isn't that important for their overall mood regulation, but the amount of nighttime light exposure really is. In other words, darkness for eight hours every night should be viewed, in my opinion, as a treatment for bipolar disorder. Not the only treatment, but it's also clear that we should all be avoiding really bright... Extensive really bright nighttime light exposure. I mean, if a- if anything, you know, my takeaway from this study is that darkness at night is the fourth key light stimulus. Now, one... A couple of things. Very bright moonlight, very bright candlelight is probably only like, gosh, three to 50 lux.

    6. PAPeter Attia1:03:24

       What?

    7. AHAndrew Huberman1:03:25

       When you go outside on a br- br- brightly lit full moon night... I encourage people to download this free app, I have no relationship to it, called Light Meter, and you... It gives you a pretty good read of what the lux are in that environment. By the way, a lot of people don't realize this. They think you just tap the button and then it tells you how many lux. You hold it down. It's kinda fun. You can scan around the room and see how many lux are on average coming from that location or outside. Go out on a really bright moonlit night.

    8. PAPeter Attia1:03:50

       I mean, we, we should have a f- full moon tonight.

    9. AHAndrew Huberman1:03:52

       Yeah, let's do it.

    10. PAPeter Attia1:03:53

        I don't have to go... Yeah.

    11. AHAndrew Huberman1:03:54

        You're not gonna get above 100 lux.

    12. PAPeter Attia1:03:55

        That's incredible.

    13. AHAndrew Huberman1:03:56

        You're sitting at a candlelight dinner with your spouse or with friends and it's clearly bright enough to see them. Put that lux meter right up, not too close to the flame, 50 to 200 lux.

    14. PAPeter Attia1:04:08

        I, I had a... Maybe 400 lux. I had, I had an interesting experience a couple of months ago on an elk hunt where it was a full moon, which actually makes the hunting not so great, but it was the first time I've ever noticed my shadow in relation to the moon. Uh, that's how bright it seemed the light was, but-

    15. AHAndrew Huberman1:04:26

        This is Halloween-appropriate-

    16. PAPeter Attia1:04:28

        Yeah, yeah, yeah.

    17. AHAndrew Huberman1:04:28

        ... since we're coming... We're, we're recording this close to Halloween.

    18. PAPeter Attia1:04:30

        So, so-

    19. AHAndrew Huberman1:04:31

        Yeah, it's remarkable.

    20. PAPeter Attia1:04:32

        ... super interesting to think it could be that dim.

    21. AHAndrew Huberman1:04:34

        Campfire, you know, and firelight.

    22. PAPeter Attia1:04:36

        Yeah.

    23. AHAndrew Huberman1:04:36

        You think, okay, gathering around a campfire. Then, okay, you know, everyone's circadian rhythm must've been disrupted for ages before the development of, of electric- electricity. No. No, th- those campfires are extremely bright, but they're, they're, they're not... They're not that bright compared to a very densely overcast day.

    24. PAPeter Attia1:04:53

        And what is your phone if you don't use any sort of, uh, light mitigating, uh, tech on it?

    25. AHAndrew Huberman1:05:00

        Well, distance matters, um, but, but-

    26. PAPeter Attia1:05:03

        But at the distance we're holding it.

    27. AHAndrew Huberman1:05:04

        Yeah, yeah, with... So with all the, the wavelengths cranked up, so no, uh... There is a nice feature intrinsic to the phone where you can eliminate the blues at night or, you know, this kinda thing, but if you crank it up to maximum light intensity, probably something like, you know, 500 to 1,000 lux. Now, keep in mind though, it's additive, right? (laughs) So it's over time. So lux is a measure of, I think, I think it relates back to candelas, is the amount of light, um, shown at I think it's like the, uh, one meter away and there's a squaring and a falling off of distance. We can look it up. Um, these are old measurmen- uh, old school measurements converted to lux, but keep in mind that if you're looking at your phone or tablet at 800 lux or 500 lux in the evening and you do that for two hours, well, you're summing quite a lot of photons. Now, it is true, and I, I, I, I do wanna be fair to the biology, uh, and it'd be dishonest to say anything different. You know, we, we've hammered on people about not shifting their circadian rhythm with light at night, but we know that the middle of the day and the middle of the night are circadian dead zones. You can't shift your circadian rhythm that well in the middle of the day and the middle of the night, but you can provide a wake-up signal for, for your body and brain. It's really that sunrise and sunset that are critical. That's why I said there are four things: see sunrise or sunrising, you don't need to see it across the horizon, sunset, bright light during the day, minimize light exposure at night. And you don't need pitch black. In fact, pitch black probably just increases the frequency of injury, you know? I get up in the middle of the night to use the bathroom probably once, I think that's normal, and go back to sleep. You know, if it were pitch black, I'd probably injure myself.

    28. PAPeter Attia1:06:40

        Yeah, I-

    29. AHAndrew Huberman1:06:40

        So just di- just dim it down. Some people use red lights. You know, our friend Rick Rubin.

    30. PAPeter Attia1:06:44

        Our mutual friend.
14. 1:08:14 – 1:13:54

    Nighttime Light Exposure; Sleep Trackers & Belief Effects

    1. PAPeter Attia1:08:14

       Here, here's something where I've, I've sorta softened my tune. So I used to be kind of a hard-liner, no blue light in the evening guy. Um, you know, had the, you know, everything was red light at night as far as my phone, using f.lux on the computer, you know, whatever it was. Um, I suspect that that matters somewhat, but I think what matters more is the stimulation that may come from those things. And what I've come to realize, at least in me, which means it probably is true in others as well, in at least some others, is that what I'm doing on my phone matters more than how bright my phone is. In other words, if I've got the best blue light filter in the world on my phone, but I'm doom-scrolling social media and getting lit up on email, that's way worse for me than if I've got my phone on maximum light and I'm, like, watching YouTube videos of F1 cars and driving around having fun. Like-

    2. AHAndrew Huberman1:09:17

       Yeah. Oh-

    3. PAPeter Attia1:09:18

       ... it's a totally different experience. So-

    4. AHAndrew Huberman1:09:19

       Yeah.

    5. PAPeter Attia1:09:19

       So, so the context matters and, um, I think f- I think for that reason, I, I would want people to be mindful of the whole picture. Um, you know, going to bed under a period of, you know, intense duress brought on by something, uh, y- you know, that's an equally dangerous component to all of this that's, that's distinct from what we're talking about.

    6. AHAndrew Huberman1:09:40

       Yeah.

    7. PAPeter Attia1:09:40

       But, but, you know, you just wanna s- I, like, I want people to be able to think of this in the context of everything.

    8. AHAndrew Huberman1:09:44

       Yeah. I, it's a really important point. Uh, you know, one thing I'll say is that if you're going to stay up past your normal bedtime, if you're gonna get a lot of light in your eyes, I would hope they will be for fun reasons and for reasons you enjoy. You should definitely spend some nights out. You should definitely do some all-nighters studying if you really, (laughs) you know, if you, if it's gonna help you get the grade that's permanent, right? I certainly have done all-nighters studying and grant writing for years. Um, you know, there are going to be the inevitable all-nighters due to, God forbid, a hos- trip to the hospital, or you heard something on the news that really amped you up, or you just simply can't sleep. Th- that stuff is gonna happen, so I think the goal should be to minimize light exposure at night. And I think what you just said is especially true because we don't know... For instance, people talk about the negative impact of social media. Is it the fact that people are looking at this little box for so many hours per day? Is it all the things they're not doing? Is it what they're looking at per se? All of those things interact and are really important. I, we know based on studies from the Stanford Sleep Lab that if you wake up in the middle of the night, looking at what time it is can be very disruptive to your ability to fall back asleep and to your sense the next day, it's just a placebo effect, but it's a powerful one, of how tired you are the next day. Y- they've done this where they wake people up in the middle of the night and then they say, "It's, you know, 4:00 AM versus 2:00 AM versus 6:00 AM," and people's perceived levels of energy during the day in some ways (laughs) correlate with what they think, how much sleep they think they got. Likewise, and this is one of the concerns, potential concerns with sleep trackers-

    9. PAPeter Attia1:11:16

       Yup.

    10. AHAndrew Huberman1:11:17

        ... Ali Crum talked about this when she came on our podcast, you know, if people see a poor sleep score, they often feel worse than if they see a good sleep score. Now, of course, physiology matters. You can't lie to yourself and say you, you know, got a great night's sleep simply by virtue of a sleep score, but I worry more about the, the false... Well, I don't know if it's a false negative that... We don't wanna put valence on this. Seeing a bad sleep score and then deciding that you're gonna have a terrible day. It, you know, I think a bad sleep score is an indication that you might need to dial some things in a bit better. S- getting a great sleep score is an indication that you might be doing a number of things right and start looking at these things as averages, wouldn't you? Would you agree?

    11. PAPeter Attia1:11:54

        Yeah, completely. I, I, I, I don't think it's that different from CGM, right? Like, I think that CGM is an amazing tool to provide insight, and you pretty much know the insights after a relatively short period of time. Y- 30 days, maybe at the outside, 90, for, for a really per- for a person with a very complicated life. Um, and you know all you need to know about how the inputs affect the output. Thereafter, if you choose to use it, it's a behavioral tool. In other words, you're using this to build in a Hawthorne effect. I think the same is largely true with sleep trackers. Um, most people have this profound sense of learning when they first encounter one of these things. And, and it's, again, you've heard it all 100 times, "Oh my God, I can't believe what alcohol does to my sleep."

    12. AHAndrew Huberman1:12:36

        Right. Or caloric trackers.

    13. PAPeter Attia1:12:38

        Exactly.

    14. AHAndrew Huberman1:12:38

        Like, I think Lane Norton's app, Carbon, I have no financial relationship to it. I use it, or, and it's taught me, wow, like, I consume a lot of calories in the form of certain things at certain times of day, and there's just a lot of good learning in that.

    15. PAPeter Attia1:12:52

        But it's the act of tracking that helps you manage it. And similarly, I think it's the act of knowing you're gonna be looking at that score that gamifies it, that kind of helps people do the right things. "Oh, you know what? I'm not gonna have that drink tonight," or, "I'm not gonna eat that snack before bed because I've now been conditioned to see how that impacts score." That said, I think that, um, you know, recovery scores and things like that are just notoriously poor at predicting performance, and, uh, I think there's a reason that serious athletes would never use things like that, um, they would tend to rely on the more tried and true methods of predicting behavior, such as-... heart rate, uh, maybe heart rate variability, but morning resting heart rate probably more predictive than anything else. And then, you know, in-workout things, such as heart rate, heart rate recovery, lactate threshold, things like that. So, yeah, I agree. I think we have to... And I say this as a guy who's generally perceived to be the most pro-device guy in the world. People would be surprised how sparingly I use things like that.

15. 1:13:54 – 1:17:21

    Light Directionality, Phone, Night

    1. AHAndrew Huberman1:13:54

       I mean, I do some tracking. Uh, not as much as you. Uh, I love things that seem to work the first time and every time in terms of our natural biology, uh, based on a couple of criteria. There's an established mechanism. Um, it's been explored in the context of pathology, like mental health disorders, as well as pro-health in healthy individuals. Um, that it'd make really good sense at the level of kind of, um, uh, wellness, uh, and, let's just say, ancient health. You know, when you're talking about getting a lot of sunlight during the day, like a lot of people will say, "Well, of course, get outside and play." Not getting too much light at night. Of course, this is just good old, quote-unquote, "good old-fashioned" advice. People spend 90% of their time indoors now. Their daytime environments are too dim. Their nighttime environments are too bright. And this kind of misleading aspect of artificial light, that when you see a bright bulb you think, "I'm getting a lot of photons," is part of the problem. And the fact that when you're out on a overcast day and it, you know, you think the sun, quote-unquote, "isn't out," well, it's hidden by cloud cover, but just think about how well you can navigate that environment without a flashlight- (laughs)

    2. PAPeter Attia1:15:10

       Yeah.

    3. AHAndrew Huberman1:15:10

       ... versus at night, where you would require a flashlight. We evolved under this dramatic difference in day/night availability of photons, independent of whether or not you can, quote, "see" the sun. And it's just very clear that our m- the... All the mechanisms in our brain and body that regulate mood are just powerfully regulated by this stuff. So, I've made it a point to really reduce the amount of nighttime light that I'm getting. But I'm less concerned about flipping on the light switch to use the bathroom as I used to be. I used to think, "Oh, I'm, like, quashing all my melatonin. This is terrible." I know I can't shift my circadian clock then. I know that that light, yes, while it's bright, if it's brief I'm not gonna worry about it too much. Would it be better to have a, you know, a dim light on as opposed to a bright light? Sure, but I'm not gonna stress it in a hotel bathroom or something. I'm not gonna walk around, you know, shielding my eyes. S- people will sometimes ask me, by the way, "Is it different to look at the phone directly versus if you tilt the phone away?" Well, it absolutely is. I mean, think about a flashlight shone on the ground in front of you, very few photons getting in your eyes, versus shone directly into your eyes. Think about ambient light from the sun going everywhere versus looking in the general direction of the sun, so east in the morning, west in the afternoon, of course. The directionality of the light matters. So, I'm not saying if, (laughs) you know, uh, that you need to, like, be- peek at your phone as if you're looking, uh, you know, over the edge of a bowl or something into it. But my friend, uh, Samer Hattaru, who's head of the chronobiology unit at the National Institutes of Mental Health, we used to room together at meetings. We stopped 'cause he's a terrible snorer. So I just could... Uh, there were a few times when I considered suffocating him in the middle of the night since he was already suffocating himself. Now, we just... We don't stay (laughs) in the same rooms anymore. We're no longer post-docs. But I caught him looking at his phone in the middle of the night, and he would tilt it, like away, like he's holding a platter for those that are just listening, and, and kind of, like, looking over at the screen there. I'm like, "What are you doing? (laughs) This is ridiculous." He said, "I'm trying not to get so much light in my eyes." That's a little extreme, but I think it illustrates the point, which is how much direct light exposure you get at night matters. How much direct sunlight exposure you get, especially early and late... Early morning, late afternoon, and throughout the day, it really matters.

16. 1:17:21 – 1:20:58

    Light Wavelengths & Sensors; Sunglasses

    1. AHAndrew Huberman1:17:21

    2. PAPeter Attia1:17:21

       Now remind me, Andrew, what is the wavelength of sunlight?

    3. AHAndrew Huberman1:17:24

       Great. So sunlight is gonna include all visible, uh, visible spectra, right?

    4. PAPeter Attia1:17:28

       Which runs from how many nanometers to what?

    5. AHAndrew Huberman1:17:29

       Yeah. So, well, let's, let's... We can answer two questions there. This wrist sensor detected 470 degree, uh, s- 70 nanometer to 650 nanometer light. So that's gonna be blue and ultraviolet. Ultraviolet's kind of high threes.

    6. PAPeter Attia1:17:43

       Yeah, that's kind of like blue to orange. So-

    7. AHAndrew Huberman1:17:45

       Yeah, blue, blue to orange. That's what this was measuring. So red light is gonna be more like 680. Um, far red is getting out to 700, 720 and up, upwards of that. Blue light is gonna fall somewhere in the, you know, low 400s. Ultraviolet is getting down into the high threes and, and lower. Um, and so these, these spectra of light... So during the day, you know, midday light, you're getting what looks like white light. You'll see, oh, the sky is blue and the sun is bright white light. It's not even yellow to your eye. And of course, don't stare at it, especially in the middle of the day. Y- you're getting all visible spectra, so you're getting everything from UV all the way out to red light. It's just coming in at equal intensities.

    8. PAPeter Attia1:18:24

       So was that a potential limitation of this study, in that it didn't have a sensor that could pick up the full spectrum of light?

    9. AHAndrew Huberman1:18:31

       Potentially, especially since they're... W- you know, we don't think of humans as UV, uh, capable. Like, we can't perceive UV light. Um, like a, a ground squirrel, for instance, can... Has UV sensors in its eyes. Turns out, you know why they use this? It's crazy. They actually... You know, when the ground squirrels sit up on their haunches, they're actually signaling one another. They rub urine on their belly and it reflects UV. Um, the, the New York Times for some reason has been running a series (laughs) of papers, uh, or articles rather, about, uh, f- naturally occurring fluorescents at night in all sorts of scorpions and, uh, monotremes like the platypus. No one really knows the reason for these odd, odd wavelength of light emissions for, for all these animals. But, you know, we view things in the blue, violet, and up to red. And, you know, uh, we're not pit vipers. We can't see far red. But we can see lower than 470 nanometers, and we can see higher than, uh, seven hund- 650.

Episode duration: 3:08:31