Essentials: Timing Light for Better Sleep, Energy & Mood | Dr. Samer Hattar

0:00:02 – Welcome to Huberman Lab Essentials,
0:00:04 where we revisit past episodes
0:00:07 for the most potent and actionable science-based tools
0:00:10 for mental health, physical health, and performance.
0:00:13 I’m Andrew Huberman,
0:00:16 and I’m a professor of neurobiology and ophthalmology
0:00:18 at Stanford School of Medicine.
0:00:21 Today, I have the pleasure of introducing Dr. Samer Hattar
0:00:23 as my guest on the Huberman Lab Podcast.
0:00:27 And now, my conversation with Dr. Samer Hattar.
0:00:30 Samer, thanks for sitting down with me.
0:00:31 – My pleasure.
0:00:33 – You are best known in scientific circles
0:00:37 for your work on how light impacts mood, learning,
0:00:41 feeding, hunger, sleep, and these sorts of topics.
0:00:46 So maybe you could just wade us into what the relationship is
0:00:49 between light and these things like mood and hunger, et cetera.
0:00:50 – Sure.
0:00:54 So, I mean, you do appreciate the effect of light for vision.
0:00:59 So when you wake up in a beautiful area, beautiful ocean,
0:01:03 light is essential, the sunrise, the sunset.
0:01:05 So that’s your conscious perception of light.
0:01:08 But light has a completely different aspect
0:01:11 that is independent of conscious vision.
0:01:14 And that’s how it regulates many important functions
0:01:15 in your body.
0:01:18 I think the best that is well-studied and well-known
0:01:20 is your circadian clock.
0:01:23 And the word circadian comes from the word circa,
0:01:25 which is approximate, and the end is day.
0:01:27 So it’s an approximate day.
0:01:29 Why is it an approximate day?
0:01:31 Because if I put you or any other human being
0:01:35 who have a normal circadian clock in a constant conditions,
0:01:38 with no information about feeding time,
0:01:41 about sleep time, about what time it is outside,
0:01:45 you still have a daily rhythm, but it’s not exactly 24 hours.
0:01:48 So it will shift out of the solar day
0:01:50 because it’s not exactly 24 hours.
0:01:51 And hence the name circadian.
0:01:54 – How does that rhythm show up in the tissues of our body?
0:01:57 – It shows up at every level that we know we studied.
0:01:59 It shows up at the level of the cell.
0:02:01 It shows up at the level of the tissue,
0:02:03 and it shows up at your behavior.
0:02:06 The most obvious for you is your sleep-wake cycle.
0:02:10 You sleep and you’re awake and sleep at the 24 hour rhythms.
0:02:13 The period length of the sleep rhythm on average
0:02:15 is 24.2 hours.
0:02:18 So you’ll be drifting 0.2 hours every day
0:02:20 out of the solar day if you don’t get the sunlight.
0:02:24 So the sunlight adjusts that approximate day
0:02:25 to an exact day.
0:02:28 So now your behavior is adjusted
0:02:31 to the light, dark environment or the solar day.
0:02:34 It’s part of the brain that is not consciously driven.
0:02:36 So you actually do not know when it happens
0:02:37 or when it doesn’t happen.
0:02:39 And that’s what we’ll get into
0:02:41 when I tell you why light affects your mood
0:02:43 and why sometimes people don’t know how to deal with light
0:02:46 to improve their mood, for example.
0:02:46 – What’s the relevance?
0:02:48 I mean, why should we care about that short difference?
0:02:49 – So let’s do the math.
0:02:51 If you shift out 0.2 hours a day,
0:02:53 in five days, you’re shifting out one hour.
0:02:56 So you’re literally one hour off
0:02:58 in your social behavior in five days.
0:03:00 In 10 days, you’re two hours off.
0:03:03 And if you’re an organism that is living in the wild,
0:03:06 shifting out of the right phase of the cycle,
0:03:09 you could either miss food or you could become food.
0:03:11 So it’s really essential for survival.
0:03:13 I think it’s one of the strongest aspects
0:03:18 of survival for animals to have the anticipation
0:03:20 and the adjustment to the solar cycle.
0:03:25 – What is the machinery that allows that to happen?
0:03:28 And how does that machinery work?
0:03:30 – Yeah. So we knew that in mammals, including us,
0:03:33 we are mammals, humans, that the eyes are required
0:03:34 for this function.
0:03:38 So if humans are born without eyes or the optic nerves are damaged,
0:03:42 humans are not able to adjust to the solar cycle.
0:03:44 So we know that the eyes are required.
0:03:48 In the human retinas, there are two types of photoreceptors.
0:03:51 They are called rods and cones because of their shapes.
0:03:54 And these rods and cones simply take the photon energy,
0:03:59 which light is made of, and they change it in a way to an electrical signal
0:04:03 that allow us to build the image of the environment in our cortices.
0:04:08 However, people have found, including me with the work of David Burson
0:04:13 and Ignacio Provencio, that there is a subset of ganglion cells.
0:04:16 The ganglion cells are the cells that leave the retina,
0:04:19 their axon, leave the retina and project to the brain.
0:04:23 So these were supposed to only relay rod and cone information
0:04:24 from the light environment to the brain.
0:04:28 We found that a small subset of these ganglion cells
0:04:32 are themselves photoreceptors that were completely missed in the retina.
0:04:37 And these are the photoreceptors that relay light environment
0:04:43 subconsciously to the areas in the brain that have and house the circadian clock
0:04:48 or the circadian pacemaker, which adjusts all the clocks in our bodies
0:04:51 to the central brain clock that allows them to entrain
0:04:53 to the 24-hour light dark cycle.
0:04:55 So these are cells that connect the eye of the brain
0:04:57 that behave like photoreceptors, essentially.
0:05:02 I think it’s worth mentioning now that people who are pattern vision blind,
0:05:07 so people who cannot see, but have eyes, many of them still have these cells,
0:05:10 these melanopsin intrinsically photosensitive cells,
0:05:16 and can essentially match or entrain, as we say, onto the light-dark cycle.
0:05:19 In fact, they possibly have no problems in circadian photoentrainment.
0:05:21 They’ll have enormous sleep-wake cycle.
0:05:22 But they’re totally blind.
0:05:24 But they are totally image-blind.
0:05:29 And what’s really interesting is that, and this story I heard from Chuck Seisler, so I’ll give him
0:05:35 credit, that some of these people who are image-blind, usually they get dry eyes and they give them a lot
0:05:35 of pain.
0:05:40 And doctors used to think, oh, since they are image-blind and they’re getting dry eye,
0:05:42 why don’t you just remove their eyes?
0:05:44 They’re not using them anymore.
0:05:48 And the minute they would remove their eyes, they start having cyclical sleep problems,
0:05:54 indicating that now they are not entraining to the light-dark cycle and are having cyclical jet
0:05:57 lags when their clock shifts through the light-dark cycle.
0:05:59 That’s really interesting.
0:06:04 And I hear from a number of blind people, a lot of them have issues with sleep, I think,
0:06:09 in part because they don’t realize that they too need to see light at particular times of
0:06:11 day or night in order to match their schedule.
0:06:18 What is the proper way to interact with light in the first part of the day?
0:06:20 Honestly, I think the easiest thing is waking up.
0:06:22 Get as much light as you can.
0:06:22 To your eyes.
0:06:24 Yeah, it’s really nice.
0:06:25 Your system is primed.
0:06:27 If you’re entrained, it’s primed to get light.
0:06:29 The sun should be out.
0:06:33 Even when it’s cloudy, you’re going to get enough intensity to help you adjust your cycle
0:06:34 to the day-night cycle.
0:06:37 These are general rules of thumb, but how long do you recommend people go outside?
0:06:40 If you do it daily, I would say 15 minutes.
0:06:42 If you don’t do it daily, you may want to increase it.
0:06:44 If you do it more, it doesn’t hurt.
0:06:48 And I’ll tell you, if you’re sensitive, you don’t even have to go in the sun.
0:06:49 You could be in the shade.
0:06:52 There’s going to be so many photons out there in the shade.
0:06:53 It’s going to be perfect.
0:06:54 Okay.
0:07:01 And if for some reason one finds themselves very far north and it’s very, very dense cloud cover,
0:07:08 how long and at what point should somebody consider using an artificial light source to mimic the sunlight?
0:07:09 Yeah.
0:07:15 Honestly, this is where we don’t have a lot of information still, because this is where we’re
0:07:21 going to discuss this maybe in more detail, that if you put humans in artificial conditions,
0:07:24 the circadian system is very sensitive to light.
0:07:32 But in reality, in the real environment, light also is affecting other aspects that are independent
0:07:34 of the setting of the circadian pacemaker.
0:07:35 Okay.
0:07:38 And these, which we call the direct effect of light on mood, for example.
0:07:43 So that is very hard to figure out what intensity you need to use.
0:07:47 And we haven’t done enough experiments because the system has been discovered just recently.
0:07:52 But yeah, I mean, if you’re, honestly, if you’re that far north and you’re in the winter
0:07:57 and you want to get, make sure you don’t use these light boxes, I would suggest that personally.
0:08:02 Okay. So I think we’ve nailed down that first part of the day. Basically, it’s get 10 to 30 minutes,
0:08:07 depending on how bright it is, and try and do that as often as possible to give the system a regulation.
0:08:13 Daily is the best. This system is really about, and you’ll see that even for the effect on depression,
0:08:18 it’s about multiple days. So you don’t have to worry if you missed it one day, you know,
0:08:23 stay longer if you want. But if you’re in a hurry and you want to do other stuff, that’s a great
0:08:27 recovery. So you might want to compensate with some extra time if you missed a day or two.
0:08:32 I’ve heard you say before, it’s entirely possible to get severely jet lagged without traveling.
0:08:32 Absolutely.
0:08:36 Simply by staying in, being on your phone too much, not getting the sunlight.
0:08:41 And you saw this during the pandemic, a lot of people mentioned that their sleep-wake cycles
0:08:47 suffered a lot. Because if you’re not going out, and if you’re staying at home, and you don’t have
0:08:53 big windows, and you’re waking late, waking up late, and then you’re using very bright light
0:08:59 till late at night, your body is going to shift. And now your day is going to start instead of like,
0:09:02 really, when the sun comes up, let’s say at six o’clock in the morning, it’s going to,
0:09:06 your day is going to start at 11 o’clock in the morning. That’s what your body is going to think
0:09:12 is the beginning of the day. So then you’re not going to be able to sleep at 10 o’clock at night,
0:09:17 because now that’s really for your body is completely different timing.
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0:12:16 that’s Roka.com and enter the code Huberman at checkout. There is this idea of chronotypes that we
0:12:22 all each intrinsically have a best rhythm of either being a morning person, you called yourself an early
0:12:28 person or a night owl or more of a kind of standard, you know, to bed around 10:30 up around seven type
0:12:34 thing. And the, and I think there are now good data, correct me if I’m wrong, from the National Institutes
0:12:41 of Mental Health and elsewhere showing that the more we deviate from that intrinsic rhythm, the more mental
0:12:43 health issues and physical health issues start to crop up.
0:12:48 So there is great data on this and there is a couple of things that complicate this. The first is
0:12:54 the people who usually are late. What do you mean? People that wake up late and go to sleep late and
0:13:00 wake up late. They, they have an overwhelmingly higher level of depression because human notice
0:13:05 that people who go to sleep early and wake up early, they do better in life. They notice that they just
0:13:10 perform better. They perform. But the question is, is, is that intrinsic to the system or is that
0:13:15 society? Because society start things usually early or late. That’s a hard question. We discriminate
0:13:20 against late risers. In a way we discriminate. And I’m not so sure that the circadian system is that
0:13:25 variable in the human population. I mean, clearly there are maybe some genetic factors that make a small
0:13:32 percentage of like everything with a bell shape. But I think most of the time, the light environment may
0:13:37 play a role. And once, as you, as we’ve talked about, this is a long-term effect of light.
0:13:44 Once you get into a rhythm, it’s hard to break out of that rhythm. Because if you start sleeping late
0:13:49 and waking up late, you’re not getting the morning sunlight. Right. And so you, you’re just going to be
0:13:58 late. It seems to me is the case is that the only way to really know if you’re meant to be an early bird,
0:14:03 as they call it, an early person or a late person, or somewhere in between, is to get morning sunlight
0:14:09 and figure out whether or not that makes you feel better. So what should people do in the afternoon
0:14:14 slash evening time in terms of their light viewing behavior? I mean, the best thing to do is to let the
0:14:21 natural light creep in into darkness, right? That would be the best. But clearly, that would be inefficient.
0:14:27 You want to go home. You want to read. You want to talk to your kids. You want to talk to your
0:14:32 family. So I think, you know, it’s nice to extend the day. I don’t think that’s wrong. If you somehow
0:14:39 can block that light from affecting your circadian clock. You do keep your home quite dim to dark at
0:14:45 night. I am an extreme, but I measured it for myself. And I asked Reiji, my wife, if she’s okay with it.
0:14:50 She also liked the dimness. Both of us can see well in dim conditions. But I think you have to measure
0:14:56 it for yourself. You really have to do it. It’s a very simple experiment. Just try to dim the light
0:15:03 as much as you can. I call it the minimum amount of light you require to see comfortably. You know,
0:15:10 use red light that is very dim if you want to keep the room for sleeping. Red light that is very dim has
0:15:18 very small effect on circadian clock. And below 10 lux of red light literally doesn’t affect sleep at all.
0:15:26 So there are ways to do it. I’ve seen you check your phone after dark once or twice. And you did it by
0:15:32 sort of pointing your phone away from you, right? It actually makes sense that, you know, if you shine
0:15:36 a flashlight in your eye, it’s much brighter than if you shine a flashlight in direct line. So if you just
0:15:41 look on the side, most of the light is going to go this way and you’re on the same. And even when I
0:15:46 check sometimes, I check it so fast and switch it off so fast. So ideally, I should not check
0:15:52 iPhones and iPads. I don’t use iPad at night because it’s hard to lower it enough because it’s a huge.
0:15:55 But even my iPhone, I try not to use it at night.
0:16:02 You had a, what I consider absolutely landmark, beautiful paper published in Nature a few years ago,
0:16:11 showing that if you disrupt the exposure to light or the timing of the exposure to light,
0:16:16 that there are dramatic effects on the stress system and on the learning and memory system.
0:16:23 So if I interpret that correctly, that could mean that when we view light and how much light
0:16:30 could make us feel happier or less happy, or even depressed, stressed, learning, etc.
0:16:31 Bingo.
0:16:35 Even if we’re sleeping and waking up at the appropriate time.
0:16:39 Bingo. I mean, eventually, because we’re talking about the whole system,
0:16:43 eventually, when you start having the other problems, you also develop sleep problems.
0:16:50 But you’re absolutely right. And in fact, now, research from Diego Fernandez in the lab
0:16:55 have found that now we know that they actually require different brain regions. So we don’t
0:17:00 only have a theory, we don’t only have a light environment that showed they can be dissociated.
0:17:06 We know that they use completely different brain regions. So the SCN that I told you about earlier,
0:17:11 the place where the central pacemaker is, the one that receives direct input from the retina,
0:17:17 through the IPRGCs to adjust your circadian clock, is not the area that receives the light input for
0:17:22 mood regulation. It’s a completely different brain region. And what’s really amazing, this region also
0:17:29 receives direct input from the IPRGCs, but projects to areas in the brain that are known to regulate mood,
0:17:35 including the ventral medial prefrontal cortex, which has been studied for many years,
0:17:45 to be impacted in a human depression. So just by this amazing serendipity, to find that a region that is
0:17:52 so deep in the advanced brain, like the prefrontal cortex is your executive brain, one of the most
0:18:00 elaborated in humans to see that they receive input from this ancient photoreceptor was stunning to us.
0:18:06 How does that finding inform daily protocols for you or for other people?
0:18:12 So that’s why we came up with the tripartite model, because as a circadian biologist, I only thought of
0:18:17 light through the circadian clock affecting behavior. As a sleep biologist, they only thought of the homeostatic
0:18:23 drive affecting sleep, affecting behavior. And for people who study light for vision and other things,
0:18:28 they thought only of the environmental input. But now if you put them all together, you get with
0:18:34 this tripartite model where it’s really mind-boggling and it makes so much sense. The organism doesn’t want
0:18:40 to depend on a single component. But if you could incorporate these three together, you could have a
0:18:46 beautiful system that is well adapted. So let me tell you the sleep-wake cycle, right? So we know there is
0:18:50 a homeostatic drive to affect sleep. You’ve had beautiful talks about that.
0:18:53 Which is basically the longer you’re awake, the more you want to be asleep.
0:18:58 So that’s your homeostatic drive. We’ve talked about the circadian influence of sleep and the fact
0:19:03 that light-dark cycle affect the circadian system, which eventually affects sleep. So these two
0:19:09 components are well understood. Now, the third factor is your direct light or environmental input. How much
0:19:15 stress, how much light you get from there also can highly impact sleep. So even if you have a good
0:19:20 circadian and homeostatic drive, if you’re getting light at the wrong time of the day or if you’re
0:19:25 being stressed and thinking, then your sleep is going to suffer. So you have to think of the three
0:19:29 together to have a beautiful sleep-wake cycle.
0:19:40 So let’s talk about food and eating and appetite. You had yet another, yes, I greatly admire your success in this
0:19:49 way, yet another incredible discovery showing that there are direct effects of light on appetite and feeding
0:19:57 behavior. So for somebody who’s interested in affecting their eating behavior, how should they use light in order to
0:20:03 adjust their eating behavior? Right. So now that I’ve told you about all these interactions between the
0:20:09 different inputs to the circadian clock, just you think about it as an engineer, what would be the
0:20:16 best thing? The best thing is to know when your food times happen in the day, when should you get light,
0:20:25 when is your circadian clock in your system? Right? So if you eat at very specific times of the day, that’s
0:20:30 another signal that is telling your body, your clock, you’re in a certain time of the day. So if you’re
0:20:35 having lunch at the correct time every day and you’re getting bright light, now you have two systems that are
0:20:41 informing your clock, your clock is going to be better. So regular mealtimes. Regular mealtimes that
0:20:48 fit your circadian clock. So, and in fact, if you do that, when I started doing this and it helped me
0:20:54 lose weight, is that I’m exposing myself to the right amount of light, dark cycle. I’m eating at regular
0:21:00 time. It is amazing. You will be not hungry. Let’s say, let’s say you eat at noon. You will not feel any hunger at
0:21:07 11:45. And then all of a sudden the hunger jumps in. This is clearly not an energy issue because it could
0:21:13 not be that drastic. Right. No, the desire to eat is mainly driven by these, these cues, these
0:21:22 hormone cues that are very exquisitely timed to sleep, wake cycle, but also to light. Exactly.
0:21:28 How regular are you, or do you recommend people be about mealtimes? Are we talking about down to the
0:21:33 minute? Absolutely not. All right. So 12 noon is my normal lunch, let’s say,
0:21:41 plus or minus? Half an hour. Okay. Yeah. So eat around between 11:30 and 12:30. If that’s the
0:21:47 time. And it depends if you also do multiple meals. Remember, three meals, that’s a decision that somebody
0:21:51 came up with. I don’t know why. Nowadays, fewer people are doing that, I think. Yeah.
0:21:56 Given our friend Sachin Panda’s work. Right. I mean, so you could have two meals. You could have
0:22:02 very multiples meals that are distributed across your active time.
0:22:06 Some people are not hungry early in the day. They might be late shifted people. Exactly. In which
0:22:10 case, eating later in the day will, will work well for them. It will work as long as they don’t eat
0:22:15 early in the morning. That’s just, you have to work with your schedule, with your active schedule.
0:22:20 What we’re talking about really is finding your ideal sleep schedule. Exactly. And finding your ideal
0:22:25 eating schedule. Exactly. And understanding how those two things interact. And you know,
0:22:30 the nice thing, as you said, finding them out is going to help you to understand how they interact,
0:22:35 because we know from the tripartite model that they are all interconnected. And for each person,
0:22:41 they’re going to be interconnected differently. It’s striking to me that in all animals,
0:22:48 besides humans, if they deviate too much from the appropriate exposure to light and light-dark cycle,
0:22:56 they essentially don’t mate and or die and or get killed off. But in humans, we are able to override
0:23:03 that at least to some extent. But the ways in which we suffer appear to be things like obesity,
0:23:08 metabolic syndromes, reproductive syndromes that accompany the other syndromes, you know,
0:23:14 endocrine syndromes, and mood and depressive disorders. Is there any effort at the level of the
0:23:23 nationally or laboratories that you’re aware of to try and use light in order to improve mood and mental
0:23:27 health? I mean, honestly, this is my moonshot. This is the thing that I think people,
0:23:33 because it’s, I say, don’t take a pill, take a photon. And not, I mean, you take pills. It’s
0:23:40 important. I’m just making it that really, we have an opportunity right now with the incredible advances
0:23:50 of LED lights, of changing spectra of light, of regulating intensities. And just for simple changes,
0:23:55 you could really improve sleep-wake cycle, productivity, and still you could actually get
0:24:02 more done. Because as we’ve talked about, when you have all these messed up, now you have to sleep
0:24:07 more, but your sleep is fragmented. It’s not very good. And you can’t focus when you can’t focus.
0:24:14 We don’t have alertness when you need the alertness. So having all these, you could allow you to do even
0:24:18 more actually at the end than less. And that’s the exciting part of it.
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0:25:48 Let’s talk about jet lag. What are the two or three things that people can do to adjust
0:25:52 their schedule quickly? Like let’s say fall classes are starting, you start a new job,
0:25:57 or you have a baby or a puppy or whatever. What is the best way to shift the clock quickly?
0:26:04 So it’s very simple as we’ve talked yesterday. So imagine you’re in the outside with no environmental,
0:26:11 with no industrial light. If your body thinks you’re in early evening and you see a bright light,
0:26:17 what does this tell you? Oh wait, this is not early evening yet. It’s still early afternoon or late
0:26:25 afternoon. So I have to delay my clock to go back to late afternoon. So if you get light early in the
0:26:30 evening, it delays your clock. So what does- Meaning that makes you want to go to sleep later?
0:26:37 Yes, it delays your clock. So later in the night, later in your night, and actually it just happens
0:26:44 that in humans, you get a temperature nadir later in the night, low temperature in your body. After that,
0:26:48 lights start advancing your clock. If I understand correctly, what you’re saying is
0:26:56 if your typical wake up time is say 7am, then your low point in temperature probably occurs somewhere
0:27:03 around 5am. And if you view light right around then, it’s going to essentially advance your clock.
0:27:09 Yeah, because then your body thinks, “Oh, it’s seven o’clock, so advance your clock by one to two hours.”
0:27:14 But if I were to view light, say at 3am, then it would probably delay my clock.
0:27:20 – Yeah. – Okay. Yeah. So, and then let’s say I land in a new schedule. I want to adjust to a new
0:27:24 schedule. Let’s say I didn’t manage to do anything with my light viewing before I went and I didn’t
0:27:31 anticipate the trip. Suddenly I’m on a new schedule, okay? I was told that one of the ways to help shift
0:27:38 the clock and to avoid gastrointestinal issues is to eat on the local schedule, to start basically
0:27:44 behaving like a local, even though your circadian clock will take a little bit of time to catch up.
0:27:49 – Absolutely. But you have to remember the light, right? So let’s, now that we explained it very
0:27:56 simply, let’s take a very simple example, right? New York to Italy. That’s a simple example. New York
0:28:02 time, Italy time, six hour difference, right? So let’s say you fly from New York at night, you reach
0:28:07 Italy at eight o’clock in the morning. What is the time in your New York time? Although you reach…
0:28:08 – Six hours back. – Six hours back.
0:28:14 – It’s 2:00 a.m. – It’s 2:00 a.m. So when you land Italy, you want to avoid light like the plague.
0:28:17 Yeah, you could eat, but you really don’t want to get a light.
0:28:19 – Right. Because otherwise it’s going to delay. – It’s going to delay you.
0:28:21 It’s going to send you to California instead of sending you to Italy.
0:28:27 – Right. What Sam is saying is so crucial. Just because getting bright light in your eyes early
0:28:31 in the day is really beneficial when you’re at home, when you travel to a new time zone,
0:28:35 you have to take into account where your body thinks you are. And so if you’re looking at the
0:28:40 Italian sunrise, having just flown from New York to Italy, and you didn’t prepare for that trip by
0:28:43 waking up a little bit earlier in anticipation. – Multiple days, yeah.
0:28:49 – And you view light at 2:00 a.m., excuse me, at 6:00 or 7:00 a.m. Italian time, beautiful Italian
0:28:54 sunrise. You are going to delay your clock. You’re going to basically throw yourself back
0:28:58 to California, but you are in Italy. You’re going to throw your biology back to California,
0:29:03 and you are going to be up in the middle of the Italian night, and you’re going to be miserable.
0:29:09 – It’s very important to avoid getting the wrong light information when you’re trying to adjust your
0:29:14 body, because otherwise it shifts you to the other side. Absolutely right.
0:29:18 – You are one of these people that has such vigor. I think a lot of your
0:29:24 ability to work hard and focus and really do so many things at an impressive level is because you
0:29:29 think about these issues, and you think about when you’re going to be optimal for focus, when you’re
0:29:35 going to be optimal for exercise, and the when is the key. And I think a lot of people live in
0:29:38 the landscape of feeling like there’s something broken inside them.
0:29:43 – I really agree with you that I think part of the reason I’m continuing to be able to do this, that
0:29:50 I really think about it, and I make sure that I keep everything aligned. And that actually helps
0:29:57 me a lot. Like I don’t suffer in sleep. I don’t suffer in waking up. I never use a timer to wake up.
0:29:59 The system is so aligned. It works.
0:30:04 – A lot of times people will say, “How come I go to sleep? I fall asleep fine, but then I wake up at
0:30:08 three or four in the morning and can’t fall back asleep.” Is it possible that those people were
0:30:10 supposed to go to bed at 8:00 PM?
0:30:15 – Yeah. I mean, it is possible. Or it’s possible that their clock is completely misaligned, that
0:30:20 they are getting maybe a nap time at night when they are supposed, and then they possibly feel so
0:30:23 sleepy in the day. So all these are possible combinations.
0:30:27 – Well, that’s an interesting idea and considered. So what they think is their sleep,
0:30:31 their body is so out of whack with the light-dark cycle that it’s actually a nap.
0:30:36 – A nap, or the weaker part of the sleep. I mean, you see this when you travel to different
0:30:42 time zones before you adjust. You go to sleep really well, but two hours later, you’re fully up.
0:30:48 Two hours. If you were so tired and this is your regular sleep, there’s no way you’re going to wake
0:30:49 up in two hours.
0:30:54 – Let’s talk about seasonality a little bit. Are there other effects of seasonality on humans
0:30:55 that we are aware of?
0:31:01 – Honestly, you could see it perfectly, I think, in Scandinavia. I mean, you could talk to people
0:31:02 who live in.
0:31:04 – Sure. They get seasonal depression.
0:31:09 – Seasonal depression is one, but actually when you start asking them questions, they tell you
0:31:15 like in the winter, they barely could wake up. They barely have the energy. Before even depression,
0:31:20 even people who don’t get seasonal depression, they’ll tell you our energy level is lower. Our
0:31:26 ability to go to work is not the same. And in the summer, most people actually sleep very little.
0:31:33 – They tell you we really can, we feel like we’re manic, we have all this energy. And not in a negative
0:31:39 way, in a funny way, right? I mean, but if you want to sleep, we have to put this curtain. I think in
0:31:46 these situations, you could really appreciate the seasonality of humans. I think we kind of destroyed
0:31:52 our seasonality because we don’t get exposed to that much natural light. We have all this artificial light.
0:31:58 – But I think honestly, one of the things that is going to happen if they follow your recommendation,
0:32:03 this is going to cause them to also experience some changes across the season because now
0:32:08 they’re going to see the sun differently. If you’re going to go out in the morning,
0:32:12 in the summer, you’re going to get a much brighter. That’s why I don’t like the change in time. I know
0:32:16 people think, oh, because you’re biased, you, because I think-
0:32:19 – Wait, wait, wait, wait. Sorry, the change in time, are you talking about daylight savings?
0:32:25 – Daylight saving. It’s such a bad idea because it disrupts that rhythm that you’re having.
0:32:30 Because I think your body, if you keep that rhythm, you will see the whole seasonality.
0:32:35 And I look at it from a different aspect than other people. If you think about it, Andrew,
0:32:40 there is a situation where you’re getting light perfectly well, and then all of a sudden they delay
0:32:45 it by one hour because, and then even though it’s the summer, your body now, if you’re still
0:32:49 not adjusting, think, oh, wait, what happened? What kind of happened?
0:32:54 – Well, I’m glad you’re bringing this up because I always thought, you know, what’s the big deal?
0:32:57 One hour, right? One hour shift, you know, spring forward, fall back.
0:32:59 – It’s so hard to adjust to one hour actually.
0:33:04 – But this goes back to the beginning of our discussion. It’s not just one hour.
0:33:04 – Right.
0:33:09 – Because it’s one hour across that one day, but there’s this cumulative effect on the clock
0:33:15 and these three elements of your tripartite model, right? The homeostatic sleep and the
0:33:19 light direct effects on mood. – And when it’s so close, it’s sometimes hard to
0:33:25 figure out how to adjust it perfectly because, you know, we’re already sleep deprived in our society.
0:33:32 And then you shift it by, you know, so it, it just, it all accumulates and it has no benefit.
0:33:34 I just don’t understand why they do this. It makes no sense.
0:33:39 – Well, I think that the reason they do it is because they don’t understand the biology.
0:33:40 – Exactly.
0:33:45 – Because one hour seems trivial, unless you understand that the repercussions of that one
0:33:51 hour shift, because what’s also clear now based on what you’re saying is that that one hour shift is
0:33:56 taking you out of alignment with the natural light, dark cycle in exactly the wrong direction.
0:33:58 – It’s pushing people to get even later.
0:33:59 – Yeah.
0:34:02 – In the summer, when light is going to push you later anyway.
0:34:06 – It’s really compounding the problem that already exists.
0:34:06 – Exactly.
0:34:14 – Samer, this has been an amazing march through the importance of light. I’m certain that people are
0:34:20 going to start thinking about how to change their relationship with light as a way to anchor
0:34:24 everything that they do and that’s important to their health. Let’s talk a little bit about where
0:34:28 people can find you. Your laboratory is at the National Institutes of Mental Health. He is head
0:34:34 of the chronobiology unit, all these things that I’ve mentioned earlier, but you are active
0:34:35 on Twitter and Instagram.
0:34:35 – Right.
0:34:37 – So what is your Twitter handle?
0:34:41 – It’s @samerhattar and I think the same for Instagram.
0:34:47 – Definitely give him a follow there and on Twitter. And I’m sure that he’ll be happy to
0:34:53 answer questions and entertain any and all discussions about chronobiology.
0:34:55 – Absolutely. Yeah. And light.
0:34:56 – Yeah.
0:34:58 – Great. Thank you, Samerh.
0:35:04 – Awesome. Thank you, Andrew.