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Cortisol Controversies

Will too many ice baths cause adrenal fatigue?


  • Online critics of cold plunge claim that a daily ice bath will put too much stress on the body, eventually causing either chronically elevated cortisol levels and/or adrenal burnout. Others claim that cold plunge will reduce cortisol spikes and help manage long-term stress.

  • Studies of cold plunge and cortisol often show a cortisol boost from a morning practice of cold plunge -- but the latest research suggests that when cortisol is already high, the ice bath will not elevate it further.

  • It's possible that a cold plunge practice will modulate cortisol levels by correcting adrenal dysfunctions, whether too high or too low -- which may explain how Mitch Wishnowsky shrunk the cortisol bubble beneath his retina and resolved his central serous retinopathy without surgery or retiring from football.

How to control excess cortisol in the NFL

Football fans might be familiar with San Francisco 49ers Australian-born punter Mitch Wishnowsky, who booted a 54-yarder during Super Bowl 2024 that pinned the Chiefs in their own end. What they might not realize is that a year earlier, doctors told Mitch that he would have to get his stress under control or undergo surgery to remove a bubble of excess cortisol from beneath his retina.

“You are way too stressed. You might have to do surgery if you don’t get your stress under control” Mitch’s doctor told him. 

Given the nature of his football career, Mitch was in no mood to reduce his stress. Instead, he opted for a regimen of Wim Hof breathwork and cold plunges.

When Mitch reported back to his eye doctor, his symptoms were gone and his retinopathy resolved.

"Doctors said 'This is incredible! You've shrunk it by so much!' " Mitch told Professor Thomas P Seager in an 2024 interview.

My doctor was sort of baffled by how quickly (my cortisol bubble) went down. The only thing I did different was breathing and cold tubs. That shows the level of stress I had and how I'm handling it. - Mitch Wishnowski, San Francisco 49'rs


Critique of Cold Plunge Critics 

Online social media is fraught with misconceptions of ice baths and cold plunge therapy. Morozko has previously debunked some of the online naysayers' warning against the extreme dangers of ice bath in Hypertension & Ice Baths. However, one of the most popular critiques circulating on social media is the misconception that regular cold plunges will lead to chronic dysfunction of adrenal glands sometimes called "adrenal fatigue" or "adrenal burnout."

Although the hyperbole of social media is great for generating clicks, Instagram influencer aren't incentivized to offer honest, reliable information. They're principally entertainers, not educators, and it can lead to come misconceptions. For example, the syndrome known as adrenal fatigue is a controversial constellation of self-reported symptoms characterized by feelings of fatigue and listlessness. It's not an medical diagnosis, per se, and it's not typically identified by abnormal adrenal makers (Cadegiani & Kater 2016).

Yet, "adrenal fatigue" is perfect for social media. The theory posits that prolonged exposure to stress could drain the adrenals (glands that secrete cortisol) leading to a low cortisol state. In turn, this adrenal depletion is supposed to cause brain fog, low energy, depressive mood, salt and sweet cravings, lightheadedness, and a myriad of other symptoms (Campos 2020). While these complaints describe real symptoms, they are not reliably associated with a physiological underperformance of the adrenals.

When blood markers of stress hormones, such as cortisol, are chronically low, endocrinologists might diagnose "primary adrenal insufficiency" (Husebye et al. 2021), not adrenal fatigue. The distinction between adrenal "fatigue" and "insufficiency" may seem semantic, but only the latter is characterized by blood markers. In addition to a general feeling of malaise, a diagnosis of adrenal insufficiency may be accompanied by weight loss, hyperpigmentation, low salt. The treatment is typically administration of exogenous steroids (such as hydrocortisone). Confusing adrenal fatigue with adrenal insufficiency could lead to unnecessary or dangerous overmedication.

The biology of stress 

To understand the physiological response to stress, one must understand two major body systems: the sympathomedullary pathway (SAM) and the hypothalamic-pituitary-adrenal (HPA) axis. The SAM is the pathway responsible for the short-term response to stress. When a short-term stress response is triggered, it sends signals to the pituitary gland and the adrenal medulla.  The adrenal medulla secretes the hormone adrenaline. This hormone gets the body ready for a fight-or-flight response, stimulating the sympathetic nervous system and reduced activity in the parasympathetic nervous system. Adrenaline also creates the physiological changes in the body, including increased sweating, increased pulse, and blood pressure.

Once the ‘threat’ is passes, the parasympathetic branch of the central nervous system can take control and bring the body back into a balanced state. When a stressful event is successfully resolved, no long-term ill effects are experienced from the short-term response. In fact, it may improve adaptive capacity -- i.e., resilience -- to future stress events. 

However, chronic, long-term stress is regulated by the HPA, rather than the SAM system. The HPA consists of the hypothalamus, pituitary gland and the adrenal glands.  For example, cortisol is produced by the adrenal glands when stimulated by the hypothalamus and pituitary.

In healthy individuals, cortisol rises rapidly in the morning, reaching a peak within 30–45 minutes of waking. It then gradually falls over the day, and rises again in late afternoon and falls in late evening. Cortisol reaches a nadir in the middle of the night. For most tests that measure cortisol levels in your blood, typical ranges are 10 to 20 micrograms per deciliter (mcg/dL) in the morning and 3 to 10 mcg/dL in the late afternoon.  However, cortisol is tricky to measure and variations are observed from lab to lab, time to time, and person to person.

Stress builds resilience 

What some popular misconceptions of stress overlook is that short-term stress can be good for you.  For example, in Ice Bath Stress I wrote about Stanford Professor Kelly McGonigal's description of the potential benefits of stress (McGonigal 2016) and in Stress Inoculation I quoted the famous Dr. Hans Seyle, who is credited with defining the modern concept of stress:

Complete freedom from stress is death. - Dr. Hans Selye (1973)

In contemporary psychology, stress is defined in two ways: the psychological perception of stress, and the body's response to it. For example, strenuous  exercise is stressful. It will cause fatigue and sometimes pain, but it will also stimulate your body to initiate physiological changes that ultimately increase strength. These adaptive responses to stress may make a person more resilient to future stress conditions.

In Ice Bath & Trauma I wrote that low cortisol is often characteristic of people who suffer from PTSD. In that case, hydrocortisone administered in conjunction with conventional talk therapy session can speed recovery (Deperrio 2019). I speculated that if an ice bath could reliably boost cortisol levels in subjects undergoing therapy for PTSD, it may aid in resolution of their trauma.

Cold exposure and effects on cortisol levels 

Morozko had previously discussed a number of studies that investigated cold exposure and its effects on cortisol. Most of these have studied short term cold exposures in the timeframe of minutes or days on healthy subjects. As one would expect, many of their results do an acute increase in cortisol levels during and after cold water immersion -- but not always. For example, in a recent study conducted by the team at the University of Oregon, the researchers exposed 16 young healthy males and females to 15 min of cold water at 10.5 degrees. Measurements of the test subjects' cortisol levels were then taken pre, 1, 15, 30 and 180 minutes post cold-water immersion (CWI) (Reed et al. 2023). At 180 minutes post-immersion, researchers measured a decrease in cortisol levels when compared to pre-immersion levels.

While it's likely that the normal diurnal cycle of waning cortisol throughout the day explains the reduction, the most interesting aspect of the study may be that the subject with the highest cortisol levels prior to cold water therapy experienced zero boost.

Cortisol data during cold water stimulation
Reed et al. (2023) tracked cortisol levels before and after cold water immersion. The results indicate that not all individuals respond alike. The subject with the greatest cortisol prior to cold stimulation experienced zero boost.

The longest duration study of cold exposure and its effect on cortisol to date remains to be the study by the Finnish team from the University of Oulu (Leppäluoto 2008). This was a 12 week study in which two groups of healthy females were exposed to either winter swimming or whole body cryotherapy three times a week. Plasma cortisol from the female subjects were measured at rest, after 5 min and 35 min of cold exposure at week 1, 2, 4, 8 and 12 intervals. After the first winter swim, the researchers observed a non-significant increase in the cortisol levels of subjects. Then, in weeks 4, 8 and 12, plasma cortisol at 15 and 35 min was significantly lower than in week 1 in the winter swimmer group. For the group that underwent whole-body cryotherapy, plasma cortisol at 15 min was significantly lower in week 4 than in week 1. By week 12, plasma cortisol at 15 and 35 min was lower than at 0 min.

Researchers opined that the long-term decrease in cortisol levels in response to 12 weeks of regular cold therapy were likely due to habituation. That is, the subjects got used to the cold, adapted to its effects, and no longer experienced an acute stress response from it.

These clinical results explain how Mitch Wishnowsky was able to reduce his excess cortisol by using a therapy thought to increase cortisol levels. His experience is supported by that of my readers, who do not report chronically elevated cortisol levels, nor the phenomenon of adrenal "burnout" as some social media influencers suggest.

As I wrote in Hormesis & Hypertension, my best guess is that a regular ice bath practice results in hormetic stress that benefits the body in the long term. It is conceivable that further well-designed studies that systematically document the long-term health outcomes from regular cold plunge therapy would overturn my current hypothesis. In addition, it would also be interesting to study how subjects with chronically low levels of cortisol (as in the case of PTSD ) respond under whole body cold water immersion over a period of several months. Although this has never been the subject of clinical research, the experiences reported to me by military veterans diagnosed with PTSD suggests that the ice bath has a therapeutic effect.


  • Campos M. 2020. Is Adrenal Fatigue Real? Harvard Health Blog.

  • Cadegiani FA, Kater CE. Adrenal fatigue does not exist: a systematic review. BMC Endocrine Disorders. 2016 Dec;16:1-6.

  • DePierro J, Lepow L, Feder A et al. Translating Molecular and Neuroendocrine Findings in Posttraumatic Stress Disorder and Resilience to Novel Therapies. Biol Psychiatry. 2019 Sep 15;86(6):454-463.

  • Husebye ES, Pearce SH, Krone NP, Kämpe O. Adrenal insufficiency. The Lancet. 2021 Feb 13;397(10274):613-29.

  • Leppäluoto, J., Westerlund, T., Huttunen, P. et al. Effects of long‐term whole‐body cold exposures on plasma concentrations of ACTH, beta‐endorphin, cortisol, catecholamines and cytokines in healthy females. Scandinavian Journal of Clinical and Laboratory Investigation, 2008, 68(2), 145–153.

  • McGonigal K. The upside of stress: Why stress is good for you, and how to get good at it. Penguin; 2016.

  • Reed EL, Chapman CL, Whittman EK et al. Cardiovascular and mood responses to an acute bout of cold water immersion. J Therm Biol. 2023 Dec;118:103727.

  • Selye H. The Evolution of the Stress Concept: The originator of the concept traces its development from the discovery in 1936 of the alarm reaction to modern therapeutic applications of syntoxic and catatoxic hormones. American scientist. 1973 Nov 1;61(6):692-9.


About the Author

Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience. Morozko Science Director Cloe Koh also contributed to this article.

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