Cortisol isn't the enemy: timing is what matters

The Short Version

Cortisol has a bad reputation, but none of these sources treats it as the enemy. What matters is when it rises, how high it goes and how long it stays up. Andrew Huberman argues that a strong cortisol pulse early in the morning, anchored by outdoor sunlight, is healthy: it raises energy, focus and immune readiness, and it sets the timer for sleep that night [1][2]. His mental health toolkit adds the other half of the rhythm: six to eight hours of real darkness at night, which on its own is linked to better mental health [3]. Dr. Sara Gottfried adds the clinical view: a "flat" or late-shifted cortisol pattern, low in the morning and high at night, is linked to anxiety, depression, PTSD and autoimmunity, and she explains how women can test for it [4]. The shared conclusion: protect the shape of the daily curve, high early and low late, rather than trying to push cortisol down across the board.

Table of contents

What They Said

Huberman on cortisol as a hormone of energy

In his episode on cortisol and adrenaline, Huberman starts by defending the hormone. "The word stress shouldn't stress you out, because you need cortisol," he says. "You don't want your cortisol levels to be too low. It's very important for immune system function, for memory, for not getting depressed" [1]. The problem is the wrong amount at the wrong time: "You just don't want your cortisol levels to be too high, and you don't want them to be elevated even to normal levels at the wrong time of day" [1]. He sums up the thesis in one line: "it's a question of how much and how long and the specific timing of release of cortisol and epinephrine as opposed to cortisol and adrenaline being good or bad. They're terrific when they're regulated. They are terrible when they're misregulated" [1].

He also covers the basic biology. Cortisol is a steroid hormone made from cholesterol, the same raw material as estrogen and testosterone, and it competes with them for it. Under stress, "more of that cholesterol is going to be devoted toward creating cortisol" [1]. The release chain starts with corticotropin-releasing hormone (CRH) in the brain, which tells the pituitary to release ACTH, which tells the adrenal glands above the kidneys to release cortisol [1]. Then comes the reframe he wants listeners to take away: "I would like you to think about cortisol not as a stress hormone, but as a hormone of energy. It produces a situation in the brain and body whereby you want to move and whereby you don't want to rest and whereby you don't want to eat. At least at first" [1].

Huberman on timing the peak with morning light

Everyone gets a daily cortisol rise that moves us from sleep into activity, and the key tool, Huberman says, is making sure the highest level comes first thing in the morning [1]. Within about 30 minutes of waking, get outside and view sunlight without sunglasses, even on overcast days [1]. His guidelines: "If it's bright outside and no cloud cover, get outside for 10 minutes. If it's a cloudy day, dense overcast, you're probably going to need about 30 minutes. If it's light cloud, broken cloud cover, it's probably going to be somewhere between 10 and 20 minutes" [1]. The reason is intensity. Morning sun with no clouds is around 100,000 lux, a cloudy day about 10,000 lux, very bright artificial light about 1,000 lux and ordinary room light 100 to 200 lux, which is why indoor bulbs and phones don't do the job [1]. Done regularly, he says, this gets "that cortisol released early in the day. That sets you up for optimal levels of energy" [1].

In his sleep episode, Huberman explains why the early peak matters for the whole day. On waking, the adrenals release a pulse of cortisol with epinephrine that raises heart rate and gets you moving, and he calls this a normal, healthy rising tide of cortisol that should come early in the day [2]. That pulse also starts a timer: about 12 to 14 hours later, the pineal gland releases melatonin, the sleepiness signal [2]. So the morning cortisol pulse helps decide when you'll feel sleepy that night.

The rhythms of cortisol and melatonin are "what we call endogenous," Huberman explains. They would continue even in a cave with no light at all [2]. But light is what anchors them. When your eyes open, melanopsin cells in the retina, discovered by his colleague David Berson, signal the suprachiasmatic nucleus, the master clock, which has "connections with essentially every cell in organ of your body" [2]. "It's vitally important that we get light communicated to this central clock in order to time the cortisol and melatonin properly," he says, because "if you don't get your cortisol and melatonin rhythms right, there are tremendously broad and bad effects on cardiovascular health, dementia, metabolic effects, learning, depression" [2].

He is especially direct about a late cortisol pulse. Referring to it as "a signature of depression and anxiety disorder," he adds that it's unclear whether it's "the cause or the effect" [2]. Either way, "Bringing that cortisol pulse earlier in your wakeful period earlier in your day has positive benefits ranging from blood pressure to mental health," and "many, many positive things happen when you are getting the cortisol early in the day far away from your melatonin pulse" [2].

The sleep episode adds finer detail to the light protocol. The clock cells respond best to the sun at a low solar angle; the eye and nervous system "don't know anything about sun rises or sunsets" [2]. You don't need to watch the sunrise, just get outside within an hour or two of it, or whenever you wake, while the sun is still low [2]. In very bright conditions, like a snowfield in Colorado in winter, "It probably takes 30 to 60 seconds to trigger the central clock and set your cortisol and melatonin rhythms properly"; two to ten minutes works for most people [2]. Stanford's Dr. Jamie Zeitzer told him that viewing sunlight through a window or windshield is 50 times less effective than being outside without sunglasses [2]. The free Light Meter app shows the gap: outdoors might read 10,000 to 20,000 lux, while a bright indoor light reads 500 to 1,000 [2]. If sunlight isn't available, blue-rich artificial light such as a sunrise simulator can help [2]. And he suspects that "about half of you that think that your night owls are just not getting enough sunlight early in the day" [2]. Pairing morning light with early exercise can make you a naturally earlier riser within two or three days [2].

Huberman on darkness at night as its own pillar

The morning peak is only half the curve. In his mental health toolkit, Huberman revised his "big six" pillars of mental health (sleep, light, movement, nutrition, social connection and stress control), changing the second from "sunlight" to "light slash dark" because "how much dark you get is also extremely important" [3]. The reason is a Nature Mental Health study of more than 85,000 people that measured light and dark exposure across the 24-hour cycle and linked it to bipolar disorder, schizophrenia, depression, PTSD and more [3]. Its key finding: "the positive effects of daytime sunlight exposure and the positive effects of nighttime dark exposure... are independent of one another" [3]. Being "in very dim to completely dark environments for a continuous six to eight hours within every 24-hour circadian cycle is correlated with much better mental health outcomes," independent "of how much light they're getting and independent of how much sleep they are getting" [3].

His practical rule: treat waking as time zero and keep roughly the 16- to 24-hour window after it dim or dark. "If you go to sleep at 10 pm and you wake up at 6 am, well, that 10 pm to 6 am phase of your circadian cycle, you should be in very dim light or entirely dark environment" [3]. He adds a study in the Proceedings of the National Academy of Sciences showing that "even having a small amount of light in the room, which isn't even that bright, while you're sleeping with eyes closed, can disrupt morning glucose levels" [3]. He isn't asking anyone to become a hermit: "Certainly go out to dinner every once in a while, go to the movies, go out and have a party, enjoy yourself," and attend to emergencies, but "to the extent that you can control it... keep your nighttime environment dim or dark" [3].

The sleep episode explains why night light is so disruptive. The longer you've been awake, the more sensitive your retina becomes, so even a little light from a screen or overhead bulb late in the evening can shift your clock [2]. He recommends as little light as possible after about 8 p.m., and especially avoiding bright light between 11 p.m. and 4 a.m. [2]. A Cell paper by David Berson and Samer Hattar showed that light at those hours, through a brain area called the habenula (sometimes called the disappointment nucleus), suppresses dopamine and can impair learning and mood [2]. Because the melanopsin cells sit mostly in the bottom half of the retina and view the upper visual field, overhead lights are worst in the evening. Dim lights placed low, candlelight and fire are better [2]. In his phrase, "the pineal is not the gland or the organ of sunlight. It is the gland of darkness" [2]. Viewing sunlight near sunset also helps: it signals the end of the day, and one study found it helps protect against the melatonin-suppressing effect of light later that night [2].

Huberman on brief spikes versus chronic elevation

Huberman's point about timing also covers the spikes that come during the day. Life delivers stressors, "Those will cause increases in cortisol and epinephrine. The key is these blips in cortisol and epinephrine need to be brief. You can't have them so often or lasting so long that you are in a state of chronic cortisol elevation or chronic epinephrine elevation" [1]. Brief spikes are useful: cortisol binds to receptors in the amygdala and learning areas, so neuroplasticity is first stimulated by attention, focus and often low-level agitation [1]. Brief stress can even protect against infection. Work associated with Bruce McEwen showed that short bouts of stress increased immune function, and a 2014 PNAS study by Kox and colleagues found that people who used Wim Hof-style breathing to raise adrenaline before an E. coli injection had greatly reduced symptoms [1]. But duration flips the effect: stress that stays high for about one to four days can protect you, while stress that lasts longer hinders immunity [1].

He describes how chronic stress becomes self-sustaining. "Normally high levels of glucocorticoid shut off the releasing hormones in the brain and in the pituitary" [1]. But stress lasting more than about four to seven days changes that loop, so the brain and pituitary respond to high cortisol by releasing even more: stress begetting stress [1]. The costs include a battered immune system, "the classic pattern of cortisol-induced body fat," cravings, and gray hair [1]. He offers a simple self-check: "If it's a short-term boudou stress, typically it blocks hunger. If it's a longer boudou stress, typically it triggers hunger in particular for these so-called comfort food, sugary and fatty foods" [1].

His defense against the chronic pattern is, again, about timing: "getting your light and your feeding and your exercise and your sleep on a consistent schedule or a consistent ish is going to be the most powerful thing you can do" [1]. His summary instruction: "Learn to control cortisol, turn it on with light in the morning, try and turn it off, and then when it spikes because of life events, learn to turn it off" [1]. For lowering cortisol, he names ashwagandha, which in otherwise healthy but stressed people reduces cortisol by 14.5 to 27.9 percent, and apigenin at 50 mg before bed, calling them the most potent non-prescription options "especially later in the day" [1]. Meal timing plays in too: after four to six hours without food, epinephrine and cortisol rise substantially, and many people benefit from eating roughly while the sun is up and stopping a couple of hours before sleep [1]. His own routine is morning sunlight, water, caffeine delayed 90 minutes to two hours, and a first meal around 11:30 or noon [1].

Sara Gottfried on testing cortisol in women

Dr. Sara Gottfried, a Harvard-trained obstetrician-gynecologist and clinical professor of integrative medicine and nutritional sciences at Thomas Jefferson University, brings the clinical and personal side [4]. She describes a "flat" cortisol pattern, low in the morning and high in the evening, and links it to anxiety, depression, PTSD and autoimmunity, and, in David Spiegel's Stanford research, lower breast cancer survival [4]. In the conversation, the late-shifted pattern is described as "not good, not good," and it "seems to have the worst immune downstream issues of any of the cortisol patterns," mapping to PTSD in veterans, autoimmunity and fibromyalgia [4].

Because the shape of the day matters, she's specific about how to measure it. She prefers saliva for cortisol because it shows free cortisol. Huberman confirms, "you get free cortisol, which is the active cortisol" [4]. Dried urine adds the metabolites, while blood gives "A static, total level", a cheaper and more limited snapshot [4]. For teenagers, whose hormonal control system is still immature and whose periods often skip under stress, she finds cortisol more informative to measure than estrogen and progesterone [4]. She wishes she had known her own cortisol levels as a stressed 27-year-old resident, because knowing early that you run high changes how you care for yourself [4].

Her own story shows what a misplaced rhythm can look like. After residency weeks of up to 120 hours, she discovered she was a "massive stress case" [4]. At 35, exhausted, gaining belly fat and uninterested in sex, she was offered a birth control pill and an antidepressant. Instead she tested herself and found her cortisol three times too high, alongside fasting insulin in the 20s, fasting glucose of 105, low progesterone and mild thyroid problems [4]. She also found that running four miles several times a week was raising her cortisol further, so she switched to Pilates and yoga. She says women doing "chronic cardio" tend to have high cortisol, and she favors about one-third cardio and two-thirds resistance training [4].

Her philosophy lines up with Huberman's refusal to treat cortisol as the enemy: "I'm not a fan of lowering stress. I'm a fan of lowering perceived stress" [4]. Her tools are an à la carte menu: meditation, yoga, breathwork, sex, connection, and feeling heard and loved [4]. Huberman described his Stanford study in which five minutes a day of cyclic sighing improved mood, lowered resting heart rate and improved sleep more than meditation or other breathing patterns [4].

When she does target cortisol with supplements, timing and testing come first. She cites multiple randomized trials showing that rhodiola rosea lowers cortisol, as does phosphatidylserine (typically 400 to 800 mg, with 400 mg more effective in trials), taken when your cortisol runs high [4]. For people with high nighttime cortisol, she mentions a combination product, Cortisol Manager by Integrative Therapeutics [4]. And she warns that supplements like phosphatidylserine are wasted money if your cortisol is normal [4]. Huberman shared his own n-of-1 experience taking rhodiola later in the day, and Gottfried called that kind of self-experiment the highest level of evidence for the individual [4].

Where They Agree, and Where They Don't

They agree that cortisol isn't the villain. Huberman calls it "a hormone of energy" and says you need it for immunity, memory and avoiding depression [1]. Gottfried says she'd rather lower perceived stress than stress itself, and warns against lowering cortisol that is already normal [4]. Both reject the idea that less cortisol is always better.

They agree that timing and duration are the real problem. Huberman warns against cortisol "elevated even to normal levels at the wrong time of day" [1] and calls a late pulse a signature of depression and anxiety [2]. Gottfried links the flat, low-morning, high-evening pattern to anxiety, depression, PTSD, autoimmunity and worse breast cancer survival [4]. Huberman's point that brief stress helps while stress lasting more than about four to seven days turns into a self-feeding loop [1] fits her picture of chronically high cortisol [4].

They agree that light and dark are the main anchors. Huberman's sleep and toolkit episodes both make morning light and nighttime darkness the foundation, and the toolkit gives darkness its own place in the second pillar [2][3]. His cortisol episode says consistent light, food, exercise and sleep are "the most powerful thing you can do" against chronic stress [1].

They partly disagree on exercise. Huberman lists sprints, weightlifting, cold and hot yoga as useful ways to raise cortisol and adrenaline briefly, and his toolkit recommends 180 to 220 minutes a week of zone 2 cardio plus a high-intensity session [1][3]. Gottfried found that her own frequent running pushed an already-high cortisol higher and says women doing "chronic cardio" tend to run high [4]. The difference is context. Huberman is describing brief, deliberate stressors for people who need more daytime energy, while Gottfried is describing women whose cortisol is already too high. For them, more of the same stress adds to the load [1][4].

They differ on the evidence for ashwagandha. Huberman cites a 14.5 to 27.9 percent cortisol reduction in otherwise healthy but stressed humans and ranks it among the most potent non-prescription options [1]. Gottfried says its evidence is mostly animal studies and traditional use, and she leans on rhodiola and phosphatidylserine, which she says have multiple randomized trials [4]. Both, however, frame supplements as secondary: Huberman says each person must check safety and ranks light, nutrition and activity ahead of any supplement [1][2], and Gottfried says they're wasted if your cortisol is normal [4].

They differ in emphasis on testing. Huberman's tools are behavioral and free; he doesn't ask listeners to measure cortisol [1][2][3]. Gottfried, a practicing clinician, wants women to know their levels, ideally from the teens or 20s, using saliva and urine to see the pattern [4]. Huberman is teaching tools anyone can use without a lab; Gottfried sees many patients whose symptoms go unexplained until someone measures.

Why It Works

The morning pulse starts the sleep timer. The waking cortisol pulse, with epinephrine, raises heart rate and alertness, and it starts a countdown to melatonin release roughly 12 to 14 hours later [2]. A pulse that comes early lands melatonin at a reasonable bedtime; a late pulse pushes both later and puts cortisol close to the melatonin window [2].

Light is the only direct input to the clock. Melanopsin retinal cells respond best to bright, low-angle sunlight and signal the suprachiasmatic nucleus, which sets clocks throughout the body [2]. Exercise and meal timing also help set the clock through a separate pathway, but light is the only direct input and far more powerful [2]. There is "no extra ocular photoreception in humans," so only light through the eyes counts [2].

The eye gets more sensitive as the day goes on. Early in the day the retina isn't very sensitive, which is why phones and indoor lights can't set the clock [2]. Late at night it is highly sensitive, so a little light can shift the clock, and light between 11 p.m. and 4 a.m. suppresses dopamine through the habenula [2]. That asymmetry is why you need bright light early and darkness late.

Darkness helps separately from light and sleep. In the Nature Mental Health data, nighttime darkness was associated with better mental health independent of daytime light and of sleep amount [3]. Even dim light during sleep can disrupt morning glucose [3].

Brief spikes switch off; chronic ones feed themselves. Normally, high glucocorticoid levels shut down the brain's releasing hormones through negative feedback [1]. After more than about four to seven days of stress, that loop turns into positive feedback, and cortisol begets more cortisol [1]. That is how a healthy daily curve can flatten into a chronic pattern, with cravings, fat gain, immune suppression and graying as downstream effects [1].

Cortisol competes with sex hormones for raw material. Because cortisol, estrogen and testosterone are all made from cholesterol, stress diverts more of it toward cortisol [1]. That helps explain why Gottfried sees cortisol, sex hormones, thyroid and gut as one connected control system in women [4].

Where It Applies, and Where It Doesn't

The morning-light, evening-dark approach applies to almost anyone: it's free, and Huberman offers it before any supplement or drug [2][3]. It's especially relevant for self-described night owls, about half of whom he suspects simply lack morning light [2], and for people with low daytime energy or poor sleep [1][2]. His outdoor times depend on brightness, from under a minute on a snowfield to about 30 minutes under dense cloud [1][2].

There are safety limits. Never look at a light that's painful; wear sunglasses when safety requires it, such as driving; and people with retinal conditions should be cautious with bright light [2][3]. Deliberate stressors like cold exposure or cyclic breathing call for a doctor's clearance, and used too often they can deplete rather than strengthen immunity [1]. Huberman also doesn't ask for perfection. Occasional late nights out, a late flight or an emergency are fine, and these systems average over time [2][3].

Gottfried's testing advice applies most clearly to women with symptoms: exhaustion, belly fat, low libido, constipation, anxiety, or periods that skip under stress [4]. Her cautions cut the other way too: lowering cortisol with supplements only makes sense if testing shows it's high, and they're wasted money if it's normal [4]. Women considering apigenin, which Huberman uses before bed to lower cortisol, should know that he describes it as "a fairly potent estrogen inhibitor" and says women who want to keep their estrogen levels up "should probably avoid apogenin altogether" [1][2]. On melatonin, which the morning pulse is meant to time naturally, Huberman's personal bias is against supplementing it, partly because tested products ranged from 15 percent of the labeled dose to 400 times more [2].

Finally, these sources don't treat the daily rhythm as a cure for serious mental illness. Huberman repeatedly advises anyone worried about a mood disorder to see a licensed clinician [3]. If you suspect your cortisol rhythm is off, ask a doctor about testing before starting supplements.

What To Do With It

1. Get outside within about 30 minutes of waking and view daylight without sunglasses: about 10 minutes on a clear morning, 10 to 20 with broken clouds, around 30 under dense overcast. A window or windshield doesn't count [1][2].
2. If you wake before sunrise, turn on bright indoor lights, then go outside once the sun is up. Where sun is scarce, a 10,000 lux lamp or other bright, blue-rich light can help [3][2].
3. Look at the sky again near sunset for a few minutes to signal the end of the day [2].
4. Dim your evenings after about 8 p.m. Use low lamps on desks or floors instead of overhead lights, dim your screens, and avoid bright light between 11 p.m. and 4 a.m. [2].
5. Protect six to eight hours of darkness every night. If you sleep 10 p.m. to 6 a.m., keep those hours dark and remove even small lights from the bedroom [3].
6. Keep a steady schedule. Wake and sleep within about an hour of your usual times, and keep light, meals, exercise and sleep roughly consistent from day to day [1][3].
7. Watch your appetite as a stress gauge. Brief stress blocks hunger; stress that drives cravings for sugary, fatty food suggests it has gone chronic and needs to be switched off [1].
8. Keep daytime stress spikes brief. Use deliberate stressors like cold or intense exercise only with a doctor's clearance and not too often. If your cortisol already runs high, favor strength training and gentler movement over "chronic cardio" [1][4].
9. If you're a woman with symptoms, ask about testing your daily curve. Gottfried prefers saliva for free cortisol and dried urine for metabolites, and suggests getting a baseline in your 20s or 30s [4].
10. Use cortisol-lowering supplements only after the basics, and only if testing shows high cortisol. Options discussed include rhodiola and phosphatidylserine (400 to 800 mg) [4] and ashwagandha and apigenin later in the day [1]. Talk to your doctor first, and note apigenin's estrogen effects [2].

Sources

1. Using Cortisol & Adrenaline to Boost Our Energy & Immune System Function · Huberman Lab
2. Master Your Sleep & Be More Alert When Awake · Huberman Lab
3. Mental Health Toolkit: Tools to Bolster Your Mood & Mental Health · Huberman Lab
4. Dr Sara Gottfried How To Optimize Female Hormone Health For Vitality Longevity · Huberman Lab