- Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today's episode is going to be all about the science of emotions.

And today, we're gonna talk in particular about something that most often is called stress. You might be thinking, wait, stress isn't an emotion, but stress really lies at the heart of whether or not our internal experience is matched well or not to our external experience or the events that are happening to us and around us.

And as you'll soon see, those converge or combine to create what we call emotions. I'd like you to come away from today's episode with what I call an organizational logic, a framework for thinking about these things that typically we just call happy or sad or depressed or anxious. And I'm going to make sure that you have tools that are grounded in physiology and neuroscience that will allow you to navigate this otherwise complex space that we call emotions that will allow you to ground yourself better when you're feeling like life is weighing on you or you're kind of being pulled by the currents of life, as well as to support other people, whether or not that's in a psychological practice, if you're a practitioner, or you have clients or children or spouses, really to be able to support other people in your environment better.

And as you may recall, the nervous system, which includes the brain and the eyes and the spinal cord, but also all the connections with the organs of the body, includes the brain and body. And those organs of the body, your gut and your liver and your spleen, they're also communicating with the brain.

So I look forward to a day, in fact, when we no longer think about neuroscience as just the brain. And many neuroscientists now also think about the body, of course, the brain controls the body, but the body is also having a very profound and concrete influence on the brain.

Today, we're going to talk about objective tools that match the brain-body experience or separate the brain-body experience in ways that leverage your ability to lean into life better, to feel better, literally, to just feel better about what you're experiencing, and believe it or not, to be able to control your emotions when that's appropriate.

Okay, so what is stress? We hear all the time that stress is bad. We hear people saying they're really stressed out. What is stress? Stress at its core is a generalized system. It wasn't designed for tigers attacking us or people attacking us. It's a system to mobilize other systems in the brain and body.

It wasn't designed for one thing. And that gives it a certain advantage in taking over the state of our brain and body, but it also gives you, all of us, an advantage in controlling it because it's based on hardwired biological mechanisms and there are hardwired biological mechanisms, meaning cells and chemicals and pathways and tissues that exist in you right now that require no neuroplasticity that allow you to put a brake on stress.

And so we're going to talk about those. So let's talk about the stress response. And by doing that, you will understand exactly why the tools I'm going to give you work. For those of you that are saying, "Wait, I just want the tools, just give me a summary." Trust me, if you understand mechanism, you are going to be in a far better position to incorporate these tools, to teach these tools to others, and to modify them as your life circumstances change.

Let's be clear about what we already know, which is that stressors can be psychological or they can be physical, okay? If I put you outside on a cold day without a jacket for a very long time, that is stressful. If I have you prepare for too many exams at once and you can't balance it all with your sleep schedule and your other needs for comfort and wellbeing like food, rest, sleep, and social connection, that is stressful.

So what happens when the stress response hits? Let's talk about the immediate or what we call the acute stress response. We could also think of this as short-term stress. So you have a collection of neurons that start right about at your neck and run down to about your navel, a little bit lower.

And those are called the sympathetic chain ganglia. When something stresses us out, either in our mind or because something enters our environment, that chain of neurons becomes activated like a bunch of dominoes falling all at once. It's very fast. When those neurons are activated, acetylcholine is released, but there are some other neurons for the aficionados out there.

They're called the post-ganglionic neurons. Those ones respond to that acetylcholine and then they release epinephrine, which is the equivalent to adrenaline. So we have this system where it's very fast. Whenever we're stressed, the core of our body, these neurons down the middle of our body, release these chemicals. And then there's adrenaline or epinephrine released at particular organs and acts in particular ways.

Some things like the muscles of your legs and your heart and other things that need to be active when you're stressed, they have a certain kind of receptor, which is called the beta receptor. And that beta receptor responds to epinephrine and blood vessels dilate. They get bigger and blood rushes in to our legs.

The heart rate speeds up. Lots of things happen that get activated. And at the same time, that epinephrine activates other receptors on certain tissues that we don't need, the ones involved in digestion, reproduction, and things of that sort that are luxuries for when things are going well, not things to pay attention to when we're stressed.

So the stress response is two pronged. It's a yes for certain things and it's a no you may not right now for other things. That's why you feel blood in certain organs and tissues of your body, but not in others. But basically you are activated in ways that support you moving.

And that's because fundamentally the stress response is just this generic thing that says, do something. You're going to feel agitated and that's because it was designed to move you. So this is important because if you want to control stress, you need to learn how to work with that agitation.

I'd like to give you a tool at this point, because I think if we go any further with a lot more science, people are going to begin to wonder if this is just going to be a kind of standard university lecture about the stress response. If you want to reduce the magnitude of the stress response, the best thing you can do is activate the other system in the body, which is designed for calming and relaxation.

And that system is called the parasympathetic nervous system. And the parasympathetic nervous system is really interesting because especially the cranial nerves, the ones that are up in the brainstem and in the neck area, those have a direct line to various features of your face, in particular, the eyes. They control things like eye movements, pupil dilation, things of that sort, as well as the tongue, the facial muscles, et cetera.

So I'm going to teach you the first tool now, so I don't overwhelm you with all this academic knowledge without giving you something useful. And the tool that, at least to my knowledge, is the fastest and most thoroughly grounded in physiology and neuroscience for calming down in a self-directed way is what's called the physiological PSY, S-I-G-H.

What I'm talking about when I refer to physiological PSYs is the very real medical school textbook relationship between the brain, the body, and the body as it relates to the breathing apparati, meaning the diaphragm and lungs, and the heart. Let's take the hallmark of the stress response. The heart starts beating faster.

Blood is shuttled to the big muscles of the body to move you away from whatever it is the stressor is, or just make you feel like you need to move or talk. Your face goes flushed, et cetera. There is, however, a way in which you can breathe that directly controls your heart rate through the interactions between the sympathetic and the parasympathetic nervous system.

Here's how it works. When you inhale, so whether or not it's through the nose or through the mouth, this skeletal muscle that's inside your body, called the diaphragm, it moves down. And that's because the lungs expand, the diaphragm moves down. Your heart actually gets a little bit bigger in that expanded space.

There's more space for the heart. And as a consequence, whatever blood is in there is now at a lower volume or moving a little bit more slowly in that larger volume than it was before you inhaled. Okay, so more space, heart gets bigger, blood moves more slowly, and there's a little group of neurons called the sinoatrial node in the heart that registers, believe it or not, those neurons pay attention to the rate of blood flow through the heart, and send a signal up to the brain that blood is moving more slowly through the heart.

The brain then sends a signal back to the heart to speed the heart up. So what this means is if you want your heart to beat faster, inhale longer, inhale more vigorously than your exhales. Now, the opposite is also true. If you want to slow your heart rate down, so stress response hits, you want to slow your heart rate down.

What you want to do is, again, capitalize on this relationship between the body, meaning the diaphragm and the heart, and the brain. Here's how it works. When you exhale, the diaphragm moves up, which makes the heart a little bit smaller. It actually gets a little more compact. Blood flows more quickly through that compact space.

The sinoatrial node registers that blood is going more quickly, sends a signal up to the brain, and the parasympathetic nervous system, some neurons in your brainstem, send a signal back to the heart to slow the heart down. So if you want to calm down quickly, you need to make your exhales longer and/or more vigorous than your inhales.

Now, the reason this is so attractive as a tool for controlling stress is that it works in real time. This doesn't involve a practice that you have to go and sit there and do anything separate from life. The physiological side is something that people naturally start doing when they've been crying and they're trying to recover some air or calm down, when they've been sobbing very hard, or when they are in claustrophobic environments.

However, the amazing thing about this thing that we call the diaphragm, the skeletal muscle, is that it's an internal organ that you can control voluntarily. So this incredible pathway that goes from brain to diaphragm through what's called the phrenic nerve, P-H-R-E-N-I-C, phrenic. The phrenic nerve innervates the diaphragm. You can control it anytime you want.

You can double up your inhales or triple up your inhales. You can exhale more than your inhales, whatever you want to do. It's such an incredible organ. And the physiological side is something that we do spontaneously. But when you're feeling stressed, you can do a double inhale. Long exhale.

Now, I just told you a minute ago that if you inhale more than you exhale, you're going to speed the heart rate up, which would promote more stress and activation. Now I'm telling you to do a double inhale exhale in order to calm down. And the reason is the double inhale exhale, which is the physiological sigh, takes advantage of the fact that when we do a double inhale, even if the second inhale is sneaking in just a tiny bit more air, 'cause it's kind of hard to get two deep inhales back to back.

You do big, deep inhale, and then another little one sneaking it in. The little sacs in your lungs, the alveoli of the lungs, your lungs aren't just two big bags, but you've got millions of little sacs throughout the lungs that actually make the surface area of your lungs as big as a tennis court.

It's amazing. If we were to just spread that out. Those tend to collapse as we get stressed and carbon dioxide builds up in our bloodstream. And that's one of the reasons we feel agitated as well. But when you do the double inhale exhale, the double inhale reinflates those little sacs of the lungs.

And then when you do the long exhale, that long exhale is now much more effective at ridding your body and bloodstream of carbon dioxide, which relaxes you very quickly. When you're feeling stressed, the physiological sigh done just one to three times. So it'd be double inhale, exhale, double inhale, exhale, maybe just two times will bring down your level of stress very, very fast.

And as far as I know, it's the fastest way to accomplish that. Be aware that if you're going to use the physiological sigh or exhale emphasize breathing to calm down, that your heart rate will take about 20 to 30 seconds to come down to baseline. And you may need to repeat the physiological sigh a few times.

So let's think about something now. Let's think about stress from not whether or not it's acute or chronic, whether or not it's good for us or bad for us, but on three different timescales, because then we can arrive at what this is all about as it relates to emotions.

But I really want you to understand the difference between the three kinds of stress on three different timescales, short-term, medium-term, and long-term, and what it's good for and what it's bad for. I think we've all heard that stress is bad for us. We've seen these pictures intended to frighten us, and indeed they are frightening.

You see the nice, really plump brain on the left says healthy or control. And then you see the brain that says stressed above it on the right, and it's like withered. Or we see that the hippocampus, an area involved in memory is smaller. People that are stressed. I think we've all heard now so many times that stress is bad but in that conversation, unfortunately, it's eclipsed some of the really positive things that stress does for us in the short-term.

When the stress response hits, that is good for your immune system. I know that might be a tough pill to swallow, but it's absolutely true. In fact, stress often comes in the form of bacterial or viral infection. And the stress response is in part organized to combat bacterial and viral infection.

So short-term stress and the release of adrenaline in particular or epinephrine, same thing, adrenaline epinephrine, is good for combating infection. And this to me is just not discussed enough, so that's why I'm discussing it here. And it relates to a particular tool that many of you ask about, but I don't often get the opportunity to talk about in such an appropriate context.

It's not that it's ever inappropriate to talk about, but what I'm about to talk about now is the use of, again, respiration, breathing, to somewhat artificially activate the stress response. And that will accomplish two things, okay? I'll return to medium and long-term stress, but I want to say short-term stress is good because the dilation of the pupils, the changes in the optics of the eyes, the quickening of the heart rate, the sharpening of your cognition.

And in fact, that short-term stress brings certain elements of the brain online that allow you to focus. Now, it narrows your focus. You're not good at seeing the so-called big picture, but it narrows your focus. It allows you to do these, what I call duration path outcome types of analysis.

It allows you to evaluate your environment, evaluate what you need to do. It primes your whole system for better cognition. It primes your immune system to combat infection. And that all makes sense when you think about the fact that famine, thirst, bacterial infections, viral infections, invaders, all of this stuff liberates a response in the body that's designed to get you to fight back against whatever stressor that happens to be, psychological, physical, bacterial, viral.

Again, the stress response is generic. The tool takes advantage of the fact that when adrenaline is released in the body from the adrenals, it has the effect of also liberating a lot of these killer cells from the immune organs, in particular from the spleen, but from elsewhere as well, and interactions with the lymphatic system that combat infection.

The way this works in the real world is best captured by a study that can be mapped back to so-called Wim Hof breathing. Now Wim Hof breathing is so named after the so-called Iceman Wim Hof. There are two components to a sort of breathing protocol that he developed that was based also on what's called TUMO breathing, T-U-M-M-O.

So before Wim, there was TUMO breathing, and many people call this now super oxygenation breathing. So it's deliberate hyperventilation. Why would somebody want to do this? Well, deliberate hyperventilation done for maybe 25 cycles. So inhale, exhale, inhale, exhale, inhale, exhale. That pattern of breathing, rapid movements of the diaphragm will liberate adrenaline from the adrenals.

When adrenaline is released in the body, you are in a better position to combat infections. And so whether or not you breathe very quickly in these cycles of 25 breaths, and regardless of what you call it, doesn't matter, adrenaline is released. If you take a cold shower, adrenaline is released.

If you go into an ice bath deliberately, and even if you do it non-deliberately, adrenaline is released. You are mimicking the stress response. And that adrenaline serves to suppress or combat incoming infections. And this was beautifully shown in a study that was published in a very fine journal, the Proceedings of the National Academy of Sciences for the US, it's literally called Proceedings of the National Academy of USA to distinguish it from other proceedings of other national academies in other countries.

The way the experiment went is that people were injected with endotoxin, or in some cases they were injected with a bacterial wall that mimics infection. It gives you a fever. It makes you feel nauseous. It makes you feel sick. It is not pleasant. Half of the people did a particular pattern of breathing that looked very much like the pattern of breathing I described a moment ago of doing 25 deep inhales and exhales followed by an exhale, holding their breath, then repeating, 25 inhales, exhales, holding their breath.

So this would look something like this, or if you're listening, it sounds like 25, 30 times, you'll start feeling heated up. You'll start feeling the adrenaline response. You're liberating adrenaline in your body. Then exhale, hold your breath for 15 seconds, and then repeat. Now, I want to emphasize, never, ever, ever do this anywhere near water.

People have passed out, so-called shallow water blackout. People have died. Please don't do it at all unless you get clearance to do it from your doctor, because there are some pulmonary effects and whatnot, and the breath holds should definitely not be done by anyone that has glaucoma or pressure concerns for the eyes, but these repeated cycles of breathing that liberate adrenaline allowed the group that did that protocol to essentially experience zero symptoms from the injection of this E.

coli, which is remarkable. They had much reduced or no symptoms. They didn't feel feverish. They didn't feel sick. They weren't vomiting, no diarrhea, which is remarkable, but makes total sense when you think about the fact that the short-term stress response, that what's typically called the acute stress response, is designed to combat all stressors.

Many of us are familiar with the experience of work, work, work, work, work, or taking care of a loved one, or stress, stress, stress, stress, stress, and then we finally relax. Maybe we even go on vacation. Like, oh, now I'm finally going to get the break, and then we get sick, and that's because the adrenaline response crashed and your immune system crashed with it.

So please understand this. Now, many of you might say, well, how long? Is it two hours? Is it three hours? A lot of you out there that really like specificity, it will vary for everybody. I would just kind of use a rule of thumb. When you are no longer able to achieve good sleep, what good sleep means to you, and please see the episodes on sleep if you want more about tools to sleep.

When you are no longer able to achieve good sleep, you are now moving from acute stress to chronic stress. You need to be able to turn the stress response off. Okay, so now let's talk about medium-term stress. Medium-term stress is going to be stress that lasts anywhere from several days to several weeks.

What is stress threshold? Well, stress threshold is actually our ability to cognitively regulate what's going on in our body. A lot of stress inoculation, a lot of managing medium-term stress on the timescale of weeks or maybe even a couple months. So we're not talking about years of stress. A lot of that has to do with raising our stress threshold.

It's about capacity. And there are very simple tools, excellent tools that will allow us to modulate our capacity for stress. And they look a lot like the tools I just described. They involve placing oneself deliberately into a situation where our adrenaline is increased somewhat, not to the extreme. And then when we feel flooded with adrenaline and normally we would panic, it's about cognitively, mentally, emotionally, calming ourselves and being comfortable with that response in our body.

And what would this look like? You can use the cyclic hyperoxygenation breathing to combat infection if you're feeling kind of run down. And there's also a way in which you can use things like cold showers, or if you exercise and you bring your heart rate up very high, you kind of go into that high intensity realm where your heart is beating a little bit harder than you're comfortable with.

The key in those moments is to learn to relax the mind while the body is very activated. One way that you can do this, and this is kind of fun, if it's approved by your physician and you're able to do this, you can bring your heart rate up. You could do this through an ice bath if that's your thing, or a cold shower, or cyclic oxygenation breathing, or you could sprint, or you could go hard on the bike, whatever it is that brings your heart rate up.

And then what you want to do is you want to actually try and calm the mind while your body is in this heightened state of activation. When we are stressed, our pupils dilate. The effect of that pupil dilation is to create tunnel vision. It literally narrows our view of the visual world.

We no longer see in panorama. And there's some other effects as well, but that's because the visual system through this cranial nerve system that I described before is tethered and is part of this autonomic nervous system. By deliberately dilating your gaze, meaning not moving your head and eyes around, but by deliberately going from tunnel vision to broader panoramic vision, literally seeing more of your environment all at once, it creates a calming effect on the mind because it releases a particular circuit in the brainstem that's associated with alertness, aka stress.

Now, this is very powerful. If you're running, for instance, and you're at max capacity or close to it, or you're kind of hitting like 80, 90% of maximum on the bike and you dilate your gaze, what you'll find is the mind can relax while the body is in full output.

And this relates to work that in various communities, people are working with this in the sports community, military communities, et cetera. But it's a form, not really of stress inoculation. It's more about raising stress threshold so that the body is going to continue to be in a high alertness, high reactivity mode, high output, but the mind is calm.

And so this isn't about unifying mind and body. This is actually about using body to bring up your level of activation, then dissociating, not the clinical dissociation kind of disorders, but dissociating the mental or emotional response from what's going on in your body. And over time, so if you do this a couple of times, you don't have to do this every workout, but if you do this every, maybe once a week or so, you start being comfortable at these higher activation states.

What once felt overwhelming and like a lot of work, now is manageable, it feels tolerable. So that's for navigating medium term stress. And then there's long-term stress. Now, long-term stress is bad. You do not want adrenaline up in your system for a very long time. In fact, ideally, you would have your stress go up various times throughout the day, but it would never stay elevated and it would never prevent you from getting a good night's sleep.

We know that chronic stress, elevated stress, and especially in the so-called type A personalities, creates heart disease, leading killer for in most every country, but in particular in the US. But by no means do you want to be stressed out all the time chronically for months and months and months and years on end.

The best tools, the best mechanisms that we know to modulate long-term stress might surprise you a little bit. First of all, there are going to be the things that don't surprise you, which is everyone knows getting regular exercise, getting good sleep, using real-time tools to try and tamp down the stress response, et cetera.

That's all going to be really useful. The data really point to the fact that social connection and certain types of social connection in particular are what are going to mitigate or reduce long-term stress. And this is a particularly important issue nowadays where we have all these proxies or surrogates for social connection.

You know, we're online and texting with people a lot. Everyone has this kind of need to stay connected to one another. Humans are incredibly social creatures. The way to think about social connection and how it can mitigate some of the long-term effects of stress is really through the systems of neuromodulation, like serotonin.

Serotonin, again, is a neuromodulator. Neuromodulators are a little bit like playlists in the brain. They tend to amplify or bias the likelihood that certain brain circuits and body circuits are going to be activated and that others will not. Serotonin generally gives us feelings of wellbeing at very high levels.

It makes us feel blissed. And it tends to make us feel like we have enough in our immediate environment. When we see somebody that we recognize and trust, serotonin is released in the brain. And that has certain positive effects on the immune system and on other systems of neural repair and synapses and things that really reinforce connections in the brain and prevent that long-term withering of connections.

So serotonin is tied to social connection. Now, social connection can take many forms. Some of those can be romantic attachments. Those could be familial attachments that are non-romantic, friendship, pets, even attachments to things that just delight us. Having a sense of delight, a sense of really enjoying something that you see and engage in, witness, or participate in, that is associated with the serotonin system.

And certainly play is one of those things, social connection of various forms. Those are things to invest in. I'll be the first to admit social connection and friendship and relationships of all kinds to animals or humans or inanimate objects takes work. It takes investment. It takes time in not needing everything to be exactly the way you want it to be.

Social connection is something that we work for, but it is incredibly powerful. Finding just a few people, even one, or an animal, or something that you delight in, believe it or not, has very positive effects on mitigating this long-term stress, on improving various aspects of our life as it relates to stress and emotionality.

Now, how do you know if you're making serotonin? You don't know in the moment, but you can learn if you pay attention to kind of recognize these feelings of comfort, trust, bliss, delight. And those are not weak terms. Those are not associated just with psychological terms. They are every bit as physiological as the movement of your muscles or the secretion of adrenaline.

Now, there are a plethora of things that will also impact wellbeing and allow you to modulate your long-term stress, reduce the likelihood that you'll engage in long-term stress. There are compounds that are not prescription compounds that can modulate the stress system. And sometimes, because of the way that life is, we just don't have the opportunity to control life and to control our response to stress.

The three I want to focus on, and one that I think you need to be cautious about that I've mentioned before, include ashwagandha, l-theanine, and melatonin. Let's talk about melatonin first. Melatonin is a hormone secreted from the pineal in direct relationship to how much darkness you are in, not emotional darkness, but light suppresses melatonin.

Melatonin helps you fall asleep. It doesn't help you stay asleep. I personally do not recommend supplementing melatonin because it's supplemented typically at very high levels, you know, one to three milligrams or even more. That is an outrageously high dose. It also has a number of potentially negative effects on the reproductive axis and hormones there.

The other is l-theanine. I've talked about l-theanine, which provided it's safe for you, can be taken 100 milligrams or 200 milligrams about a 30 minutes or 60 minutes before sleep. It can enhance the transition to sleep and depth of sleep for many people. It increases GABA, this inhibitory neurotransmitter in the brain.

It tends to turn off our forebrain a little bit or reduce the activity of our kind of thinking systems and ruminating systems help people fall asleep. But theanine has also been shown for people that are chronically anxious or chronically stressed to significantly increase relaxation. It is known to have a minor effect on anxiety, but eight studies have shown that.

It definitely has a notable effect on stress. The other supplement that can be very useful is ashwagandha. Ashwagandha is known to lower anxiety and cortisol. This is great. I mean, the opportunity for me anyway, to be able to take something that can help me reduce my cortisol so that I don't get some of the long-term effects of stress.

And I'm not going to take ashwagandha year round. I would only do this if I was feeling like I wasn't managing my short and medium-term stress well. So I don't take it on a regular basis. I do take it when I'm in these times when things are particularly stressful.

So social connection and some supplementation, of course, diet, exercise, sleep for long-term stress. So I hope today you were able to take a slightly different view of this thing that we call stress, not just see it as evil, but see it as powerful and useful in certain contexts, great for us in certain contexts, and problematic in other contexts.

And as well to think about the various tools that I've presented that can allow you to adjust and modulate your internal levels of alertness or calmness so that you can lean more effectively into life, which includes sleep and social connection and the work you have to do. And of course, acknowledges that the events in the world are beyond our control.

What's in our control is how we react to them. Something that's commonly said in the wellness and self-help and psychology world, but for which there often aren't as many concrete tools that we can really look to and trust in real time. As always, really appreciate your time and attention today.

I hope you practice some of the tools if they're right for you. I hope you think hard about stress and how you can control your stress. And above all, as always, thank you for your interest in science. (upbeat music)