How to Reclaim Your Brain in 2026 - Dr Andrew Huberman - #1042

**Chris Williamson** (0:00)
Most people think about cortisol as a bad thing that you want less of. Is that the right way to think about it?

**Andrew D. Huberman** (0:07)
Not at all. Cortisol has been labeled a stress hormone, and it is involved in stress. We have a bout of stress, you get a spike of cortisol, so to speak. Cortisol, like other stored hormones, is bound to things, and there's a free form of cortisol. That's the active one. You don't want your free unbound cortisol to be chronically high. But we need to really think about why it was called a stress hormone in the first place. And the main reason is cortisol's job is to deploy energy sources for your brain and body to be able to react to things, think and move. So cortisol naturally goes up a bit during stress, and it comes back again, provided you don't ruminate on that stress too much, on the stressor, that is. The big eye-opener for me was when I actually went into the modern textbooks on cortisol. Not the ones that most medical students learn from, but what the endocrinologists, the specialists really learn from, and what the circadian and sleep biologists now understand, which is the reason you wake up every single morning, even if you have an alarm clock, is because of something called the cortisol awakening response. So if we just step back from a typical healthy 24 hours, it looks something like this. A couple hours before sleep, your cortisol is low, your heart rate's low, you're calm. Hopefully it's dim in the room. You go to sleep. Your cortisol is then at its absolute lowest levels for the entire 24 hours. And by the way, this is the same time when melatonin, the sleepy hormone, is at its highest levels. After about four or five hours of sleep, and typically in that first four or five hours of sleep is when you get your most deep sleep, slow wave sleep, non-REM sleep, many people experience a transition into the sort of last third of their sleep for the night. And they tend to wake up around that time. And often they use the restroom and go back to sleep. Why did they wake up? Well, it turns out that your cortisol is starting to rise about two thirds of the way through the night. I mean, it's really creeping up throughout the entire night, but it's gone from this nadir to it's starting to climb. And then at some point, let's assume you get back to sleep or you slept through the night. At some point, maybe 6 a.m., maybe 8 a.m., depends on who you are and what your schedule is, you wake up. Maybe your alarm clock goes off. You wake up. You wake up because the cortisol level reached a certain threshold, is literally the cortisol awakening response. It is healthy, it is good. And if I were to measure your cortisol at that moment and compare it to what people might call like a stress episode in the afternoon, you would say it's much higher than what stress induced. Okay, so then your cortisol continues to rise, and there's this unique opportunity in the first hour, or maybe 90 minutes, but in the first hour after waking, where viewing bright light can increase your morning cortisol spike, as I'll refer to it, by up to 50%.
Bright light can come from sunlight, ideally, or from a bright artificial light, like a 10,000 lux artificial light, or even a very bright indoor artificial LED or incandescent light. Okay, why is this important? Well, we could explore all the biology of cortisol, and we can summarize it by saying you have this hypothalamic, pituitary adrenal axis that sets off cortisol, self-regulates, negative feedback loop, et cetera, et cetera. That's the normal regulation of cortisol, which basically can be summarized as it never allows you to have your cortisol too high for too long. It feeds back on itself and shuts it down. However, in the first hour after waking, your brain's circadian clock has a unique privileged pathway that is separate from the HPA axis, where it can amplify cortisol only in that first hour. So you say, why would that be? This is nature's evolutionarily hardwired mechanism for giving you the opportunity to boost your cortisol so that you have energy to lean into the activities of your day. And when I say energy, I'm not saying, you know, it's not like we happen to be in California at the moment, but not energy, energy. I'm talking about glucose mobilization. If you're on a low carbohydrate diet, you're going to mobilize other energy sources. Your brain and body wakes up because of cortisol. You have the opportunity to boost that wakefulness even further by viewing bright light. Yes, you could exercise. Yes, you could drink caffeine. It turns out caffeine, if you're a chronic caffeine user, such as me, such as you, doesn't actually increase cortisol that much. You could jump in a 40 degree Fahrenheit cold plunge. Doesn't actually increase your cortisol. All this nonsense going around the internet about, you know, women shouldn't do a cold plunge, and if they do, not as cold. Okay, maybe, but it's always attributed to increases in cortisol. Cold plunge reduces your cortisol levels. You can look at the data. The data show that it goes down. Adrenaline goes up, dopamine goes up, norepinephrine go up. So cortisol makes you alert. It makes you focus. And here's the key thing, spiking your cortisol in that first hour after waking is so, so important because that negative feedback loop mechanism kicks in about three hours after you've been awake. And that's why your cortisol then starts to drop late morning, early afternoon, later afternoon. And in the afternoon, if you have a bout of stress, no problem. You just have a little bit of cortisol bump, adrenaline bump, and it goes back down. If you don't spike your morning cortisol, what ends up happening is your cortisol system, essentially the HPA axis, is primed for stress events to give you big lasting increases in cortisol later, which make it hard to fall asleep, which make it hard to stay asleep, which are part of the reason why people have afternoon anxiety, all sorts of things. So you're actually supposed to feel a little stressed first thing in the morning. This is normal, this is healthy, and it sets you up for being more calm in the afternoon. Now, none of this is tied to whether or not you wake up at 8 a.m., 6 a.m., 4 a.m., or 11 a.m. This is not about chronotype. This is simply about the first hour after waking, but after about 90 minutes post waking, that opportunity to spike your cortisol goes away. So if you can't view bright light in the form of sunlight, get it from artificial light. You would do well to compound that with hydration, which by the way, for reasons that still aren't entirely understood, it probably has to do with some electrolyte balance, et cetera, first thing in the day, will also burst your cortisol. If you can't get in, exercise right away, even just some skipping rope, jumping jacks, this kind of thing, getting the body into a high cortisol state early sets you up for being in a low cortisol state in the afternoon and evening. And any cortisol that you might trigger through a stress event will quickly subside, unless what's called flattening your cortisol curve by not spiking in the morning. And by the way, the curve that I'm describing, being high in the morning, lower into the afternoon, low, low, low, as you get into the first hours of sleep, this is the healthy cortisol curve for men, women, kids, pregnant women. Post-menopausal women, it tends to flatten out a bit, and they need to do additional things to get that spike earlier. So this is when I hear all this stuff about don't cold plunge, it increases cortisol, it doesn't increase cortisol. And also this notion that we're supposed to avoid stress entirely, not true. You and I both generally agree on that. But how you time your stress is important. And the last point I'll make is that if you were to do, say, a very intense workout in the late afternoon evening, it's been demonstrated that will triple or quadruple your baseline cortisol levels for a few hours. Not a problem. You can take a hot shower afterwards, do some slow breathing and calm down, provided you didn't fill up with caffeine prior, you could probably fall asleep just fine. But because you spiked your cortisol late day, what you find is that the next day cortisol is lower, which is one of the, not the only reason, but one of the reasons why you're a bit more sluggish the next morning. So, and this is why people's, if they exercise too late in the day, their rhythm starts to shift. When we talk about your circadian rhythm shifting in response to light, it's the cortisol peak that's shifting or flattening, which in turn adjusts your melatonin peak and trough.