Key takeaways
- Your stress response has a fast arm, adrenaline, and a slower arm, cortisol, and both are meant to switch off once a threat passes4.
- The famous “inverted U” curve of stress and performance traces back to a 1908 study of dancing mice, with groups as small as two animals and no statistics7.
- In a 2024 review of 35 trials, learning to see stress as helpful improved task performance only slightly, and less after accounting for studies that likely went unpublished11.
- “Cortisol face” isn’t a medical term; the real disease of excess cortisol, Cushing’s syndrome, most often comes from steroid medicines, and the kind the body causes itself is rare36.
- In 2004, the FTC sued the marketers of CortiSlim, a pill promoted to control cortisol; by 2007 they had settled without admitting wrongdoing and given up at least $12 million12.
In mid-2003, marketers began selling a supplement called CortiSlim. Its pitch: control cortisol, the body’s main stress hormone, and the pounds would come off fast1.
The ads were built to look like talk shows, not commercials2. By August 2004, the Food and Drug Administration had sent the marketer a warning letter, and in late September the Federal Trade Commission (FTC) sued1.
The FTC charged that the weight-loss promises were false or unsubstantiated. In settlements that admitted no wrongdoing, seven marketers of CortiSlim and a sister product gave up at least $12 million in cash and assets2.
Two decades later, cortisol is a social media star again. Videos about “cortisol face,” a puffy, rounded look blamed on stress, have drawn millions of views3.
Both stories miss the same point. Your stress response is a lifesaving system built for short emergencies, and it’s meant to shut off afterward. Once you know how it runs, it’s easier to tell which claims fit the biology and which ones sell a product.
Two alarms: one fast, one slower
A stressor is anything, physical or mental, that knocks your body off its steady state4.
The fast alarm. Your sympathetic nerves and the inner core of your adrenal glands, which sit on top of the kidneys, release adrenaline (also called epinephrine) and noradrenaline46. Your heart beats faster and harder, blood pressure climbs, airways widen and blood sugar rises4. Digestion slows, attention narrows and pain fades into the background4. This is the classic “fight or flight” setup4.
The slower alarm. At the same time, a chain of messages runs from the brain to the adrenals. Scientists call it the HPA axis, for hypothalamus, pituitary and adrenal4.
The hypothalamus sends a signal hormone to the pituitary gland, which sends another, called ACTH, to the outer layer of the adrenal glands. They release cortisol4. Cortisol keeps fuel in your blood, holds back insulin and calms inflammation and immune activity4.
The brakes. The system has a built-in off switch. Part of the brain, the hippocampus, sends feedback that helps rein in cortisol release4. Once the threat passes, the body is meant to return to baseline4.
Trouble starts when the alarm keeps ringing. Long-running activation of both arms is linked to hardened arteries, immune changes, gut problems, anxiety and depression4. Our upcoming article on chronic stress covers that side.
Cortisol runs on a daily clock, not just on stress
Cortisol isn’t only an emergency hormone. It also helps regulate blood sugar, metabolism, blood pressure and inflammation every day5.
Your levels rise and fall on a schedule. They’re normally highest in the morning and much lower by around 4 p.m., according to MedlinePlus, the National Library of Medicine’s health site5. They drop again after you fall asleep6.
That rhythm explains why one cortisol number means little on its own. Stress, exercise, pregnancy, heat or cold, and some medicines, including birth control pills, can all change a result5.
For readers who trust the body’s own wisdom, this is a reassuring story. The stress system has an accelerator, a clock and brakes. Most of the time it works without any help from a pill.
Your stress response, decoded, plus a 60-second reset
Our own table, built from the sources cited: the top rows describe a normal alarm, the bottom rows signs worth taking to a clinician.
| What you notice | What’s happening in your body | Useful, or a sign to get checked? |
|---|---|---|
| Pounding heart, faster breathing | Adrenaline speeds the heart and widens airways4 | Useful; should settle when the threat passes4 |
| A sinking stomach or “butterflies” | Blood flow to the gut drops and digestion slows4 | Useful short term |
| Sudden sharp focus | Alertness and vigilance rise4 | Useful |
| Not noticing a scrape until later | Stress hormones dull pain4 | Useful in an emergency; check yourself afterward |
| A jolt of energy | Blood sugar rises for quick fuel4 | Useful |
| Feeling keyed up for weeks or months | Both alarms stay switched on4 | Talk with a clinician |
| Sad, empty or hopeless most days for two weeks or more | Possible depression15 | Get checked |
| Dizziness on standing, salt craving, darkening skin, weight loss | Possible signs of Addison’s disease13 | Get checked |
| Wide purple stretch marks, a fatty hump between the shoulders, easy bruising | Possible signs of Cushing’s syndrome6 | Get checked |
| Thoughts of death or suicide | A crisis sign15 | Call or text 988 now |
The 60-second “after the alarm” reset. This routine is ours. It borrows the idea of reappraisal, which has small benefits in trials11, but the routine as a whole hasn’t been tested. Try it after a near miss, a hard call or a startle:
- Breathe out long. Let three breaths out run a little slower than the breaths in. No counting needed.
- Name it. Say to yourself, “That was my alarm doing its job.”
- Unclench. Drop your shoulders, loosen your jaw and open your hands.
- Look around. Name three things you can see right now.
- Pick a next step. If the threat is real, act. If it has passed, choose one small task and start it.
Our article on relaxation methods before bed and the upcoming article on beginner breathing exercises offer longer practices.
A little stress can sharpen you, but the famous curve rests on 1908 mice
A short burst of stress lets the body push harder than usual, notes StatPearls, a medical reference hosted by the National Library of Medicine4. That’s the kernel of truth behind a chart you may have seen at work: the “inverted U,” where performance rises with arousal and then falls when you’re overwhelmed.
The curve usually carries the names of psychologists Yerkes and Dodson. Their 1908 study looked at how task difficulty and stress affected how well dancing mice learned to tell two choices apart7.
The study had no statistical analysis, and some groups held as few as two mice, notes David Diamond, a researcher at the University of South Florida7. Later work in cats, rats and people found a similar pattern, and the finding hardened into the “Yerkes-Dodson law“7.
Not everyone accepts the law. A 2026 review in the journal Music Performance Research traced how the idea changed over the 20th century. The authors called its evidence limited and inconsistent and its history contested, and they urged music researchers to use it with caution8.
The fair summary: some arousal helps you rise to a challenge, but no law fixes where your peak sits.
Seeing stress as fuel helps a little, in tests so far
If stress can help, can believing that help more? Psychologist Alia Crum and her colleagues tested this.
In studies published in 2013, employees watched short videos that framed stress as either improving or harmful9. Those shown the “improving” videos reported better health and work performance9. A later study from Crum’s group found healthier responses to a lab stress test after a single 3-minute “improving” video9. Her team has since noted that those early studies tracked effects for only hours or days9.
In 2023, the same lab tested a fuller “Rethink Stress” program at work. In one experiment, technical job performance rose equally with or without it, though people-skills ratings improved only with the program; in a second, the technical effect was borderline9. Most outcomes were self-reported9.
A larger test came in 2022. Psychologist David Yeager of the University of Texas at Austin led six studies of high school and college students, with samples ranging from 118 to 2,71710. A 30-minute online lesson combined two messages: abilities can grow, and a racing heart can help you perform10.
Students who took it showed better heart and blood-vessel responses to a stress test and lower cortisol, and they reported less anxiety during the 2020 school closures10. Funding came partly from the National Institutes of Health, along with the National Science Foundation, Google’s Empathy Lab and the Jacobs Foundation10. All the stressors were school-related10.
The best overall view comes from a 2024 meta-analysis, a study that pools other studies, by Michel Bosshard and Patrick Gomez in Scientific Reports11. Across 35 randomized trials with 5,638 people, reappraising stress gave task performance a small lift11. Adjusting for studies that likely went unpublished shrank the effect by about 40%, though it didn’t vanish11. Mindset-only lessons, without other content, showed no clear effect11.
The authors’ verdict: helpful, but not a silver bullet11.
Not everyone fights or flees: the case for “tend and befriend”
In 2000, psychologist Shelley Taylor and colleagues at UCLA pointed out a gap. Before 1995, women made up only about 17% of participants in lab studies of the body’s stress hormones12. Of 14,548 people in 200 stress studies they reviewed, 66% were men12.
Taylor’s team argued that fight or flight doesn’t describe women’s behavior well. They proposed another pattern: “tending” to children and “befriending” others, building social ties that protect and support12.
The authors said the basic adrenaline and cortisol responses are similar in both sexes12. They suggested that oxytocin, a hormone tied to bonding, works with estrogen and the body’s own opioids to shape the difference12. They called this a model, and they said the roles of those hormones remained to be seen12. The work was funded by the National Science Foundation, the National Institute of Mental Health and the MacArthur Foundation12.
The idea resonates with natural-health values: community, caregiving and connection as part of how humans cope. The mechanism is still a hypothesis. Reaching for people under stress is a sound instinct either way, and our upcoming article on social support goes further.
Cortisol went viral before, but the science still doesn’t support the fixes
Doctors don’t use the phrases “cortisol face” or “moon face,” according to Christie Turin More, an endocrinologist, or hormone specialist, at the University of Colorado3. Cortisol that stays high for a long time can put weight on the face, she notes, but by itself a full face says little about your hormones3.
Her test is a pattern, not a selfie. True cortisol excess brings several changes at once, and they stick around3. By her reasoning, a face that slims down after a new diet or supplement is a clue that cortisol was never the problem, and she isn’t aware of any diet that rebalances cortisol3.
Besides suing CortiSlim’s marketers, the FTC had sent more than 25 warning letters by late 2004 to other companies making similar cortisol-control weight-loss claims1. “Paying for fad science is a good way to lose cash, not pounds,” said Deborah Platt Majoras, then FTC chairman2.
A related claim, that stress wears out your adrenal glands, goes by the name “adrenal fatigue.” Our article on hormone-balancing claims explains why researchers haven’t found evidence it exists.
How strong is the evidence?
| Claim | What the research shows | Evidence level |
|---|---|---|
| Adrenaline and cortisol prepare you for short emergencies, including hard physical effort | Well-mapped physiology4 | |
| Performance peaks at moderate arousal (the “inverted U”) | Pattern seen in animals and people7; a 2026 review calls the evidence limited and inconsistent8 | |
| Seeing stress as helpful improves performance | 35 trials; small effect that shrinks after bias adjustment11 | |
| “Tend and befriend” hormone mechanism | A theoretical model; roles of oxytocin unproven12 | |
| Everyday stress causes “cortisol face” | A round face alone is hard to link to cortisol3 | |
| Pills that “control cortisol” for weight loss | FTC alleged CortiSlim’s claims were false or unsubstantiated2 |
Real cortisol diseases look different from a stressful year
Most people who develop Cushing’s syndrome, long-term excess cortisol, get it from medicine: long-term, high-dose glucocorticoids, the steroids prescribed for asthma, rheumatoid arthritis or lupus6. The version the body causes on its own is rare. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) puts it at 40 to 70 cases per million people, mostly adults 30 to 50, with women affected about three times as often as men6.
When levels stay very high, the changes are hard to miss: weight gain over thin arms and legs, a rounder face, extra fat at the base of the neck or a hump between the shoulders, bruises that come easily, broad purple stretch marks and weak muscles6. No single test settles it, so doctors usually rely on two of three: cortisol in a 24-hour urine sample, in late-night saliva, or in blood after a small dose of the steroid dexamethasone6.
A hard year can raise cortisol without causing the disease. NIDDK notes that depression, anxiety, heavy drinking, poorly controlled diabetes and obesity can push levels up at times, a pattern doctors call pseudo-Cushing’s6.
Addison’s disease is the opposite: too little cortisol. MedlinePlus lists extreme tiredness and weakness, weight loss, nausea, belly pain, darkening skin, salt craving and dizziness on standing13. Symptoms often show up during an infection or other stress13. Signs of adrenal crisis, such as belly pain, trouble breathing, dizziness and reduced alertness, call for the emergency shot if one was prescribed; without it, call 911 or go to an emergency room13.
When stress itself needs help. Low mood, hopelessness, loss of interest and changes in sleep or appetite are signs of depression when they last most of the day, nearly every day, for two weeks, says the National Institute of Mental Health15. A clinician can help sort out what’s going on.
If you’re struggling or having thoughts of suicide, call or text 988 to reach the 988 Suicide & Crisis Lifeline. In a life-threatening emergency, call 91115.
Measuring stress: a questionnaire tells you more than a spit test
Researchers often measure stress with the Perceived Stress Scale, created by Sheldon Cohen and colleagues in 198314. It asks 10 questions about how often your life felt stressful over the past month, each rated from 0 for never to 4 for very often14. Totals run from 0 to 40, and higher means more stress14.
Saliva cortisol tests are a different matter. They have a real medical use: a late-night saliva test is one of the standard checks for Cushing’s syndrome, because cortisol should be low at that hour6.
As a general “stress test,” though, a cortisol reading is shaky. Results swing with the time of day, recent stress, exercise, temperature and medicines5. A cortisol test alone can’t tell what’s causing a high or low level, so doctors usually need follow-up tests5. A home kit that reads one sample can’t carry that much weight.
Your own signals often tell you more. Notice how fast you settle after a stressor, how you sleep, and whether your mood has shifted for weeks. Those patterns are worth bringing to a clinician.
Questions readers ask
Can stress really change my face?
Very high cortisol over a long period can add fat to the face3. But a round face alone is hard to blame on cortisol, and real cortisol excess comes with other signs that persist36.
Should I take a supplement to lower cortisol?
The University of Colorado endocrinologist we cite knows of no diet that balances cortisol3, and the FTC has acted against cortisol-control weight-loss claims12. If you suspect a hormone problem, ask for the specific tests above.
Is all stress bad for me?
No. Short bursts can sharpen focus and briefly lift performance4. The concern is an alarm that stays on for weeks or months4.
Do women and men respond to stress differently?
The core hormone responses look similar, but Shelley Taylor’s team proposed that women more often respond by tending and befriending12. That idea is still a model12.
The bottom line
The stress response is one of the body’s best tools. Adrenaline and cortisol get you through an emergency, then the system is built to settle down. A little stress can even help, though the famous curve and the “stress is good” lessons are shakier and smaller than popular advice suggests.
What the biology doesn’t support is a pill, a drink or a saliva kit that promises to fix your cortisol. Real cortisol diseases have specific signs and specific tests. Stress that lingers, darkens your mood or brings thoughts of suicide calls for help from a person, starting with a clinician or a call or text to 988.
Related reading
About this article
This article was researched from federal health agencies, FTC records, peer-reviewed studies and university sources, listed below, and reviewed in October 2026. It is general education, not medical advice..
Sources
- SupplySide Supplement Journal. “Cortisol-control Dietary Supplements Draw FTC Attention.” November 8, 2004 (trade press, cited for events only). supplysidesj.com
- Federal Trade Commission. “Federal Trade Commission Reaches ‘New Year’s’ Resolutions with Four Major Weight-Control Pill Marketers.” Press release, January 4, 2007. ftc.gov
- Shaw T. “Do You Think You Have a ‘Cortisol Face’? What You Should Know About This TikTok Trend.” University of Colorado Anschutz Medical Campus, November 25, 2024. news.cuanschutz.edu
- Chu B, Marwaha K, Sanvictores T, Awosika AO, Ayers D. “Physiology, Stress Reaction.” StatPearls, NCBI Bookshelf, updated May 7, 2024. ncbi.nlm.nih.gov
- MedlinePlus. “Cortisol Test.” National Library of Medicine, updated December 23, 2024. medlineplus.gov
- National Institute of Diabetes and Digestive and Kidney Diseases. “Cushing’s Syndrome.” National Institutes of Health, last reviewed May 2018. niddk.nih.gov
- Diamond DM. “Cognitive, Endocrine and Mechanistic Perspectives on Non-Linear Relationships between Arousal and Brain Function.” Nonlinearity in Biology, Toxicology and Medicine, 2005;3(1):1-7 (University of South Florida record). digitalcommons.usf.edu
- Rivera K, Smyth L, West S, Pike-Rowney G. “From mice to music: a historical critique of optimal arousal in music performance.” Music Performance Research, 2026;13:1-37 (Australian National University record). researchportalplus.anu.edu.au
- Crum AJ, Santoro E, Handley-Miner I, et al. “Evaluation of the ‘Rethink Stress’ Mindset Intervention: A Metacognitive Approach to Changing Mindsets.” Journal of Experimental Psychology: General, 2023 (Stanford Mind & Body Lab copy). mbl.stanford.edu
- Eunice Kennedy Shriver National Institute of Child Health and Human Development. “Online tool helps protect adolescents from stress, NIH-funded study suggests.” Science Update on Yeager DS, et al., Nature 2022, July 2022. nichd.nih.gov
- Bosshard M, Gomez P. “Effectiveness of stress arousal reappraisal and stress-is-enhancing mindset interventions on task performance outcomes: a meta-analysis of randomized controlled trials.” Scientific Reports, 2024;14:7923 (University of Bern repository). pubmed.ncbi.nlm.nih.gov
- Taylor SE, Klein LC, Lewis BP, Gruenewald TL, Gurung RAR, Updegraff JA. “Biobehavioral responses to stress in females: Tend-and-befriend, not fight-or-flight.” Psychological Review, 2000;107(3):411-429 (UCLA copy). taylorlab.psych.ucla.edu
- MedlinePlus. “Addison disease.” Medical Encyclopedia, National Library of Medicine, reviewed April 24, 2025. medlineplus.gov
- “The Effect of Mindset Interventions on Stress and Academic Motivation in College Students.” Innovative Higher Education (Springer), 2024. link.springer.com
- National Institute of Mental Health. “Depression.” NIH Publication No. 24-MH-8079, revised 2024. nimh.nih.gov