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Cognition & Cold Water

Updated: Jan 23

Your ice bath is probably good for your brain

Squinting Thomas P Seager, PhD with Pacific Ocean in background.
Caring for my brain is essential for my career as a scientist. This is me, at the beach in Monterey CA on one of my research trips working for the US Navy on infrastructure systems, getting my deliberate cold exposure between workshops and presentations.


  • Cold plunge activates the sympathetic nervous system "fight-or-flight" response, interrupting cognitive processes that are not associated with immediate survival.

  • Acclimation to cold water therapy protects against formation of phosphorylate tau proteins in the brain (one of the hallmarks of Alzheimer's disease) by recruiting brown fat and strengthening thermoregulatory processes.

  • When activated by the cold, brown fat secretes neuroprotective hormones.

  • The neuroprotective aspects of cold water therapy may make ice baths suitable for people managing brain injuries.

Ice Bath Afterdrop

The most dangerous thing about my 14 minute ice bath was probably the 20 minute drive I made afterwards. - Thomas P Seager, PhD

My afterdrop was so bad that I shook for 10 minutes. I had no fine motor control, and I had to wait until I could operate my stick shift before I could speed off to my hot yoga class to rewarm.

Little did I know that my body was probably recovering faster than my brain.

Is my ice bath making me stupid?

Although research has shown that ten sessions of whole-body cryotherapy can improve memory in cognitively impaired individuals (Ramaszweska et al. 2018), a new article concludes that short-term cold exposure results in immediate loss of cognitive function (Falla 2021). Having reviewed 18 separate experimental studies, the authors wrote "Cold exposure induced an impairment of cognitive performance even before accidental hypothermia was established."

These findings sound alarming.

Brain health is not the kind of photogenic quality that attracts Instagram followers in our media-saturated culture, but it's one of the most important aspects of my career, my self-esteem, and my identity.

I spent over six years in graduate school to earn a doctorate in engineering. It took me ten more years to earn tenure. I moved my family and my young children through four different cities, chasing research grants, building laboratories, mentoring graduate students, and climbing in academic prestige. My whole life has been like one enormous smartness contest.

When Patrick Porter, PhD (right) measured my biological age with his BrainTap technology, and told me I was 30 years old -- two years younger than when he measured me a year ago -- I was both proud and relieved.

My Mother is not so fortunate.

The brain can age faster than the body

As I explained in Brown Fat for Brain Health, my Mother's brain is already gone. She suffers from advanced Alzheimer's dementia.

Back in 2018, before I knew anything about the metabolic origins of Alzheimer's (e.g., Kellar & Craft 2020) Mom was in a bad way. She was refusing her medications, physically abusing her nurses, and resisting her own care.

Her doctors told us that her behavior had become unmanageable.

I told them to discontinue all of her medications.

"To hell with her cholesterol," I said. "I will not have my Mother lose a power struggle over the little remaining agency she has over her own bodily integrity. "It is not dignified."

Mom's health, mood, and behavior improved right after we discontinued her statins, and that experience become part of my own health awakening.

Parents aren't so smart

As I child, I thought my parents were the smartest people in the world. I know that's a natural position for any child to take, but my impression survived the usual rebelliousness, cynicism and disillusionment that comes with adolescence, because they had a lot of evidence on their side.

My parents met in graduate school at Harvard. My Father was a Professor of Education at the University of Pittsburgh, and my school teachers, principals, and administrators were all his former students -- or at least it seemed that way to me. He wasn't just the smartest man in my child world. The admiration and respect my teachers held for my Father meant that he seemed like the smartest man in their world, too.

He also had complex diet requirements that resulted from his extensive food allergies. So when my Mother read Diet for a Small Planet (Lappé 1971) and changed our meals towards more plant-based, more industrialized (e.g., margarine instead of butter), less fat, and more carbohydrates, I didn't see that as the act of political ideology that it was.

I thought it was because my parents were smarter.

As it turned out, the corn oil margarine, the skim milk, the breakfast cereals, the corn syrup concentrates... they were all contributing to my childhood obesity and her cognitive decline.

I don't want what she's going through now to happen to me.

The ice bath is a workout for your brain

Whole body cold water immersion causes your body to produce a flood of neurotransmitters that alter brain functions. For example, plasma concentrations of norepinephrine and dopamine were increased by 530% and 250% respectively in young men immersed in 14C water (Šrámek et al. 2000). Because these chemicals act directly on our brains, they regulate biological impulses and emotions that drive changes in our mood, behavior, and thinking (Butnariua 2019).

One illustration of this effect is called ice face, and my daughter Emma exemplifies the phenomenon in the video below. It takes about 30 seconds for the norepinephrine synthesized near the kidneys to each the brain. At that point, after the gasp reflex has subsided and the pain of vasoconstriction is escalating, norepinephrine takes over the brain.

In Emma's case, the 30 second mark corresponds to the moment when she breaks into a smile and begins singing along with her music. At this point, there is little her brain can do but experience the biochemical changes taking place.

It wouldn't be a good idea to test her memory, her mathematical problem-solving skills, or her ability to maintain focused attention on cognitive tasks.

In short, her brain is busy.

It's no wonder that testing immediately after cold exposure reveals impaired cognitive performance.

Consider an analogy with exercising our muscles. When we work out, we fatigue our muscles and induce production of anabolic hormones like testosterone that stimulate recovery and growth of muscle tissues. During this period immediately after our workout, our muscles perform poorly -- not because we have made them weaker, but because they are busy becoming stronger.

Just like our muscles do not perform well when recovering, neither can our brains be expected to perform well when operating under the biochemical hormone rush of cold exposure. The immediate loss of cognitive performance experienced during rewarming after an ice bath is not an indication of some permanent injury -- it is consistent with a hormetic dose-response to healthy stress.

This explains the discordance between the studies that measure short-term reduced cognitive function immediately after cold exposure, and the studies that measure improved cognitive performance over the longer term.

Brain benefits of the ice bath

Despite the short-term interruption of cognitive functions, there are several mechanisms by which deliberate cold exposure promotes brain health: 1) improving insulin sensitivity, 2) protecting against hypothermia by recruiting brown fat, and 3) stimulating brown fat to produce fibroblast growth factor 21 (FGF21), a hormone with neuroprotective properties (Tournissac et al. 2019).

Cold exposure improves insulin sensitivity

As I wrote in Deliberate Cold Exposure for Diabetes, inducing cold thermogenesis is one of the best ways to clear excess glucose from your blood stream, improve glucose tolerance, and increase insulin sensitivity. For example, researchers in Poland studied 14 women who practiced winter swimming in the Baltic Sea between the months of October and April. Water temperatures ranged between 1 and 9.5C, and they swam for 5-10 minutes, at least twice a week. The cold water winter swimmers experienced a significant improvement in insulin sensitivity, compared to a control group who swam indoors in warmer water. Because separate research has documented a link between insulin resistance and neurological disorders (e.g., Kellar & Craft 2020) the increased insulin sensitivity exhibited in regular cold water swimmers is likely helps protect the brain against metabolic dysfunction.

Thermogenesis protects against tau phosphorylation in the brain

One the principal mechanisms by which cold exposure improves metabolic function is by the activation and recruitment of brown fat. Unlike white fat, brown fat is dense with mitochondria capable of keeping the body warm during cold exposure in a a process called non-shivering thermogenesis. The sole purpose of non-shivering thermogenesis is to breakdown glucose and fats (including triglycerides) from the bloodstream to produce heat to keep the body warm. As a consequence, people who are acclimated to cold exposure have improved thermoregulatory function and maintain warmer body temperatures under cold challenges that would cause hypothermia in others. That's important because even a small reduction in body temperature (mild hypothermia) can produce tau phosphorylated neurofibrillary tangles in the brain -- one of the characteristic physiological markers of Alzheimer's. In healthy people, these reverse upon rewarming, but in people with impaired thermoregulatory systems, like elderly people without brown fat, chronic hypothermia can result in permanent tau phosphorylation. Recent research showed that cold-acclimated mice "were completely resistant to tau hyperphosphorylation in the hippocampus" -- even when subjected to a 24-hour cold challenge (Tournissac et al. 2019).

Brown fat activation produces neuroprotective hormone FGF21

The principal research focus with regard to brown fat has been related to its therapeutic potential to remedy metabolic disorders. However, it is now clear that brown fat is also a secretory organ, producing critical important hormones that the body depends upon to modulate other functions, including the thyroid and the brain. For example, in The Thyroid Connection to Cold I wrote about how brown fat produces hormones that modulate thyroid function and can resolve disorders like Hashimoto's thyroiditis. But it's only recently that I learned about the potential for brown fat to secrete FGF21. According to Canadian researchers, cold-acclimated mice can have 66% more FGF21 circulating through their bloodstream after cold exposure, compared to controls (e.g., Tournissac et al. 2019). According to their study, FGF21 can reverse induced cognitive deficits in rats, reduce blood-brain barrier disruptions, and protects against neurotoxicity.

What about ice baths for people with brain injury?

I recently got a call from a woman who does cold showers with her husband, a former Navy SEAL recovering from traumatic brain injury. She may have seen Justin Hoagland's article 'Deliberate Cold Exposure' about treating his symptoms of multiple sclerosis with his Forge.

She wanted to know if advancing from cold showers to ice baths would be helpful for her husband, or introduce new risks?

Because I'm not a medical doctor, I forwarded her question to our medical advisory board. Dr. Davisson Edmond, a Morozko customer and general practitioner, was kind enough to write me back.

He said:

Ice is very protective of brain cells and good for all types of inflammation.

The medical science supports his assertion. According to Misiak & Kiejna (2012):

There is also convincing evidence supporting the neuroprotective role of low temperatures, which originates from experimental studies on the application of therapeutic hypothermia in infants and adults with hypoxic-ischemic cerebral injury. - Misiak & Kienna 2012.

Recent randomized-controlled trials found that whole body cryotherapy improved memory and attention on standardized tests of cognitive performance in patients with mild cognitive impairment (Ramaszweska et al. 2021, Senczyszyn et al. 2021). What's more, hypothermia has long been recognized as a restorative therapy for patients experiencing brain injury due to lack of oxygen, such as after heart attack, drowning, or asphyxiation (e.g., Drury 2010).

That doesn't speak to or recommend cold water therapy for any specific patient or injury. For example, just because people with the most vulnerable brains -- infants, elderly, and injured -- are benefiting from a little bit of cryo doesn't mean that those of us with healthy brains will achieve analogous results. But it is consistent with the good results I'm getting from Porter's BrainTap measurements, and considering those, I'm going to continue the practice of what's been working for me


UPDATE 11 June 2022

I got an email from Hollywood stuntman Chris Balualua a few weeks ago. He is a gymnast, freestylist, martial artist, and tricker of extraordinary skill and showmanship. Chris worked on a big-budget Hollywood movie, in which he sustained over 40 traumatic blows to the head during rehearsal and filming of a fight sequence.

His brain injuries were so extensive that he couldn't sleep at all for 300 straight days.

Cases like his are so rare that most doctors believe it is impossible for a human being to survive under such sleep-deprived conditions. However, there is at least one documented case of severe brain injury preventing sleep.

Paul Kern was a Hungarian solider who reportedly did not sleep for four decades after being shot in the head.

Chris emailed me because he saw a local TV news spot about the health benefits of the ice bath, and he wanted to try it for himself.

My daughter Emma (pictured above) is a Krav Maga Instructor, and worked as a stunt coordinator on several short films. She's a certified Morozko Method Deliberate Cold Exposure Guide, and she agreed to take Chris through his first plunge.

Chris spent 5 minutes in the Forge -- most of it shivering uncontrollably. He rewarmed in the sunshine outside our Studios in Phoenix AZ and reported to me later that he felt sharper, smarter, and had more mental stamina the rest of his morning.

I went in a Morozko Forge and filmed my 5 minute session. It made huge impact on my brain and body! - Chris Balualua, stuntman

Because Chris' condition is so rare, he has embarked on a program of self-directed research and experimentation to discover what works best for him.

He just sent me a study that showed cold water swimming stimulated stem cell activity in brain-injured rats, and that pre-cooling improved their performance on cognitive tests.

Data suggest pretreatment with cold water swimming could promote proliferation of endothelial progenitor cells and ameliorate cognitive deficits of experimental traumatic brain injury. - Zhou et al (2017)

By some lucky coincidence, I met with Justin Hoagland again a few days after my meeting with Chris. Although I knew Justin had been deployed in Mosul, Iraq as a Navy SEAL, what I didn't know is that he also suffered traumatic brain injury.

Justin's injury was caused by blast waves, rather than blunt force. As Dr. Kirk Parsley, himself a former Navy SEAL, explained it to us, when the shock waves from a powerful blast travel through the brain, they cause differential displacement of sections with different densities. The effect is to tear the brain apart from the inside, meaning that the damage is very difficult to detect.

Like Chris, Justin reports that his ice bath practice helps improve his cognitive function, and has been critical to his long-term brain recovery.

The combination of these exceptional experiences, and the scientific studies regarding the effects of cold water immersion and the brain, help reinforce the hypothesis that an ice bath may help slow the ageing of my own brain, and delay loss of cognitive function that typically accompanies old age.

UPDATE 7 Jan 2024

An email came in from a 65 year-old reader who experienced transient global amnesia after a cold plunge. He said that he was an experienced with cold water therapy, and he does winter hikes in boots and shorts. However, after a recent cold plunge in his home-made horse trough, he lost his memory.

This time I experienced this transient amnesia condition, and so of course I’m looking for information to inform whether I continue this dunking or not -- especially since my spouse & probably others view this as a high risk for mental capacity or effect on the brain.  - 65 year old reader from Northwest United States.

According to Lewis (1998) "transient global amnesia (TGA) is an inability to form new memories (anterograde amnesia). TGA lasts less than 24 hours, and is not associated with other focal neurological signs or symptoms." The causes remain mysterious, although the condition has been described in the scientific literature for more than fifty years.

Nonetheless, risk factors have recently been described:

Close precipitating events for TGA are considered emotional stress (i.e., triggered by gastric endoscopy, birth/death announcement, and difficult/exhausting workday), physical effort (i.e., gardening, house work, and sawing wood), physical exertion (including sexual activity), and water contact / temperature change (i.e., hot bath/shower and cold swim). - Portaro et al. 2018

While temperature shock is among the risk factors, and epidemiological data show that TGA is more frequent during cold weather (Akkawi et al. 2006), the one thing that all of these risk factors have in common is activation of the sympathetic nervous system.

It has been shown that psychogenic amnesia can be linked to several psychiatric disorders including post-traumatic stress disorder (PTSD) and dissociative disorders, where the loss of memory could be considered a defensive psychological mechanism. - Portaro et al. 2018

That is, TGA is associated with the fight-or-flight response -- especially in the seventh year of life or later. Because cold water shock causes sympathetic activation, it makes sense that an ice bath could trigger a temporary amnesia.

What's not yet clear is whether TGA should be considered a Contraindication to Cold Plunge. Case studies in the scientific literature suggest that TGA is typically benign and without long-term sequela.

Nonetheless, sometimes an ice bath practice can sometimes call up strong emotions from deep within the central nervous system. In the case of TGA, it seems that these emotions can interfere with cognitive functions in ways that are more serious than the typical brain fog that I wrote about in Don't Ice Bath Overdose.

No one can tell you whether the resolution of TGA is found in avoiding whole-body cold water immersion, or in exploring the psychological antecedents of sympathetic activation. In Should I Shiver? I wrote about the potential for shivering to release stress from the central nervous system that might otherwise be held as trauma.

When I posted a clip on trembling from my podcast with Mike Mutzel, an outpouring of replies came from women who experienced trembling after childbirth -- particularly postoperative trembling after C-section. Petere Levine, PhD writes that this trembling is a release of stress from the central nervous system that protects against post-traumatic stress disorder (PTSD).

Given the association between cold shock and TGA, Levine's work makes me wonder if shivering in the ice bath could protect against amnesia, too.

That's not a recommendation. I'm not telling you what you should do or predicting what might happen for you. Instead, treat my wondering like a question, or a request.

If you experience temporary amnesia after your ice bath, and decide to try shivering, will you let us know about your experiences?


  • Akkawi NM, Agosti C, Grassi M, Borroni B, Pezzini A, Vignolo LA, Padovani A. Weather conditions and transient global amnesia. Journal of neurology. 2006 Feb 1;253(2)

  • Lewis SL. Aetiology of transient global amnesia. The Lancet. 1998 Aug 1;352(9125):397-9

  • Portaro S, Naro A, Cimino V, Maresca G, Corallo F, Morabito R, Calabrò RS. Risk factors of transient global amnesia: Three case reports. Medicine. 2018 Oct;97(41)


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.

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