It's rare you come across a behavior or tool that's so powerful across almost every facet of health.
Cold exposure is front and center and but it's too expansive so we're going to zero down into mental health.
Since it's just a tad in focus these days.
There's fascinating new research (led by Chris Palmer's book, Brain Energy) on how metabolism may be a critical piece of what drives mental health, and we have already looked in detail at how early trauma, infection, and stress can hyperactivate immune function and inflammation later in life.
Metabolism and inflammation. Again…right in cold exposure's wheelhouse.
Here are the areas we'll cover:
- A quick intro to how cold exposure works
- Cold exposure and the mental health
- Cold exposure and dopamine
- Cold exposure and serotonin
- Cold exposure and BDNF
- Cold exposure and cortisol (stress)
- Cold exposure and brain inflammation
- Cold exposure and anxiety
- Cold exposure and depression
- Cold exposure and acetylcholine
- Cold exposure and neuroprotection
- Cold exposure and the brain area battle for supremacy
Let's get started!
A quick intro to how cold exposure works
All the current longevity tools revolve around energy. The lack-there-of really.
- Rapamycin - mimics famine
- Acarbose - keeps glucose from spiking
- SIRT- cellular shock protein from energy signals
- AMPK - housekeeping mode from famine signals
Turns out that there are ancient pathways that turn on when we're faced with hardship:
- Lack of oxygen
- Cold exposure!
Cold exposure, as little as 5-10 minutes in 60-degree water is showing fascinating research across almost every pathway looked at!
Huberman labs have a great review, and Wim Hoff is becoming a legend. We also like Dr. Seiger's barrage of research.
We originally came across cold exposure in our dopamine rescue guide but quickly went down the rabbit hole.
You can't find a pathway not positively affected.
Even the new issue around amyloid clotting! See our top 10 for healthy clot removal.
Cold exposure has powerful effects on the following systems which will figure greatly into mental health:
- CE rebalances metabolic function centered around glucose and fat processing
- CE ramps up metabolism due to brown fat conversion
- CE improves cardiovascular function
- CE improves mitochondrial function - the power plants of every cell
- CE greatly supports immune function and inflammatory states
- CE stimulates steroidal hormone pathways
Goodness..just the root of almost every modern health epidemic these days!
So…let's start to look at mental health specifically which rests squarely on everything just listed.
Cold exposure and the mental health
If we had to pick two from the above list, we would focus on steroidal hormones and the immune system (inflammation).
They're all intimately tied (poor metabolism drives inflammation, etc).
We did giant reviews on how early trauma, infection, and stress (even in utero) can drive mental health issues later in life.
This is inflammation at its core!
Since we can go a 1000 different directions, let's take each of those macro improvements and tie them to mental health before digging into some of the weeds below.
CE rebalances metabolic function centered around glucose and fat processing
Dr. Chris Palmer and his new best-selling book, Brain Energy are leading the charge here.
We looked at the whole fat piece (omega 6 versus 3) for brain function and mental health.
The net net:
Convincing evidence shows that psychiatric conditions are characterized by an increased risk of metabolic syndrome (MetS), a clustering of cardiovascular risk factors including dyslipidemia, abdominal obesity, hypertension, and hyperglycemia.
Not surprising since the brain is made out of fats primarily and runs on glucose.
We've covered the problem with glucose but it's front and center:
In prospective analyses, men in the highest tertile of sugar intake from sweet food/beverages had a 23% increased odds of incident CMD after 5 years (95% CI: 1.02, 1.48) independent of health behaviours, socio-demographic and diet-related factors, adiposity and other diseases.
Cold exposure has a powerful effect on glucose and fats. Cold exposure tricks the body into thinking it's in extreme peril!
The body immediately sucks glucose up into muscle to be ready for action.
The impact on insulin and lipids (fats) is equally powerful.
A great deal of this is tied to cold exposure's effect on fat. Let's go there now!
CE ramps up metabolism due to brown fat conversion
Babies can't shiver. So to keep warm, they have large deposits of brown fat. Unlike 'white" fat…the one we're very familiar with which is primarily a means of storage, brown fat is metabolically active.
It actually burns energy! The "brown" color is from higher levels of mitochondria, the power plants of our cells, in brown fat.
As we gain the shiver response, we lose brown fat (or most of it). Cold exposure can actually convert white to brown (or beige) fat with time!
This increases metabolism and energy sources for all cells including your brain!
Now…follow this as it gets really interesting.
One of many effects from cold exposure is a significant boost to a pathway called PGC-1α, a key player in creating new mitochondria (the "browning" process of fat).
Only temperature significantly affected PGC-1α protein levels (p=0.045).
PGC-1α is implicated in the pathophysiology of many neurodegenerative disorders;
This gets back to the Brain Energy book thesis. Brain energy is the key to healthy function.
If you read our review of depression, you see a form of atrophy…a disintegration of brain areas.
PGC-1α is also necessary for synaptogenesis in the developing brain and the generation and maintenance of synapses in postnatal life.
Goodness…synaptogenesis…making new connections is depression's kryptonite!
We'll touch base on the brain's fertilizer, BDNF below but it's how CBD, psilocybin, exercise, and SSRIs (till tolerance build up) have any impact!
Let's dive a little deeper into the brain energy aspect!
CE improves mitochondrial function - the power plants of every cell
That's the technical term for making new cellular power plants, and it's a critical nexus between mental health and cold exposure.
Remember that the "brown" in brown fat is from the density of mitochondria (technically, the iron content in them).
First, newer research is really pointing to energy deficiencies in the brain and pretty much every mental health issue out there:
Several studies have found a relationship between mitochondrial dysfunction and mood disorders, such as major depressive disorder and bipolar disorder. Impairments in energy production are found in these disorders together with higher levels of oxidative stress.
You have the most common issue (depression) and a key development disease (bipolar).
Here's where it gets interesting (to us, anyway).
Early trauma, stress, and infection can affect mitochondria function (and mental health) later in life!:
Preclinical evidence suggests that alterations in mitochondrial function and structure are linked to both early stress and systemic biological dysfunction.
Oxidative stress (the damage from oxygen) in the brain is a key link between both.
In driving more energy production (mitochondria), cold exposure also ramps up the protection and waste removal side (oxidative stress):
systematic cold stimulates intrinsic protective resources by enhancing oxidative processes, which in turn initiates activation of the antioxidant systems and increases the overall resistance of the body to stress factors of different types.
Goodness…cold is stress-proofing the brain at the cellular level!
PGC-1α from above is just one key player.
It even goes to glutathione, our key detox and antioxidant in the body and brain:
The baseline concentration of GSH and the activities of erythrocytic SOD and Cat, were higher in winter swimmers. We interpret this as an adaptative response to repeated oxidative stress, and postulate it as a new basic molecular mechanism of increased tolerance to environmental stress.
See more on glutathione for anxiety.
Let's turn to inflammation in the brain!
CE greatly supports immune function and inflammatory states
The new research around mental health really falls squarely in the immune system and inflammatory states.
This is the early trauma, infection, and stress piece which gets marked up into our epigenome…potentially for life!
Let's drop the hammer:
Cold exposure protects from neuroinflammation through immunologic reprogramming
Goodness…" immunologic reprogramming".
Turns out that there's a competition between cold exposure modifications and…hyperactive immune responses.
Autoimmunity. Neuroinflammation. Basically, 2/3rds of our modern diseases.
The body can't fight cold AND fight itself (via the immune system) at the same time. Too costly to do both.
We have big reviews on neuroinflammation or editing immune system markups.
For long term healing, this is the key and cold exposure is a powerful tool!
One note…proper immune function is required to detect and kill wayward cells (cancer or virally infected, etc).
Here's the beauty..cold exposure actually has powerful anti-cancer effects which reflect proper immune response!
there is accumulating evidence that daily brief cold stress can increase both numbers and activity of peripheral cytotoxic T lymphocytes and natural killer cells, the major effectors of adaptive and innate tumor immunity, respectively.
So…cold exposure boosts immunity when needed (cancer) but calms it when needed (autoimmune).
It "modulates" it! The Holy Grail (see medicinal mushrooms).
Alright. Those are broad strokes. Let's zero into discreet pathways!
We'll start with a cascade of powerful players.
Cold exposure and dopamine
This is really the monster player with cold. For good reason.
The brain thinks we're in impending danger. It doesn't know we're going to hop out after a few minutes and an entire cavalry cascade occurs.
The front and center is the fight or flight side of the autonomic nervous system.
The heavy hitters here are adrenaline (norepinephrine) and as a result…dopamine.
This makes sense as dopamine is about zeroing our focus on survival-related targets and movement!
We think of dopamine as a pleasure player, but that's not really true. It's more of a reward driver.
Here's the fascinating piece…low dopamine feels really really bad (depression), and no dopamine feels…like crushing despair. Dr. Huberman's review on dopamine goes into that. Must listen.
Dopamine is tricky though…if you spike it, it will subsequently drop by an equal or greater amount!
Strange see-saw relationship with pain (physical and emotional).
Cold exposure is one of the few ways you can raise the baseline or tonic dopamine levels…for long periods of time!
The effects are powerful with cold exposure:
Plasma noradrenaline and dopamine concentrations were increased by 530% and by 250%
That's 2 ½ times more than sex (a huge driver of dopamine) and even more than nicotine. Both of which have "refractory" or rebound periods.
There are powerful connections between dopamine and depression, bipolar, schizophrenia (literally a disease of dopamine mismatch), and more.
Cold exposure is one of the few ways we can increase it without the pushback that nature built into the pain/pleasure system.
It's intimately tied to other powerful neurotransmitters including our next one.
Cold exposure and serotonin
Serotonin is our "feel right in our skin" player as manager of ALL human behavior but there's a side hustle.
Serotonin is a primary stress response buffer!
The brain uses it to temper your mood, energy, and pain sensitivity in times when we're in jeopardy (stress).
That's why your mood drops when you're sick…literally, the conversion of tryptophan to serotonin is turned down.
The relationship with cold exposure is a curious one.
First, serotonin will drop during the cold exposure activity itself. Makes sense…intense stress!
But…cold exposure has a powerful effect on inflammation and serotonin also gets it signal from the immune system.
Viruses and bacteria make more of themselves from tryptophan so the body will squash conversion to starve them out (which starves out our serotonin).
Inflammation is the "signal" from the immune system to serotonin, and when it drops, serotonin gets the all clear!
Further, cold suppresses autoreactive T cell priming and pathogenicity through the modulation of monocytes, thereby ameliorating neuroinflammation.
That's the whole autoimmune trade-off from above.
Less brain inflammation (or gut) means more serotonin longer term.
One note…early trauma, infection, or stress (even in utero) can downregulate serotonin throughout life by this very mechanism. Increases systemic inflammation (hyperactive immune system)!
Right that ship first! Check out our review on serotonin or why the immune system is the future of mental health.
One key result from serotonin is your new best friend for mental health. BDNF.
Cold exposure and BDNF
BDNF is the secret superstar of mental health and addiction.
It's the brain's fertilizer and in daily opposition to:
- Loss of steroidal hormones
- Hyperactive immune response
Goodness…outgunned in many cases.
So…cold exposure's effect there since it's a downstream result of serotonin function?
the Ucp-1 gene potentiation following cold stress is associated with the enhancement of Bdnf, signaling in brain after 6 h and bone after 5 days
Okay…we need to introduce Ucp-1. Uncoupling protein 1.
Basically, it takes some of the cellular energy production offline to leak out heat. That's the primary mechanism in brown fat to warm us back up.
This effect of UCP1 and BDNF is more fascinating!
Essentially, the body is detecting stress/damage (cold storm) and calling in the repair crews.
Check out our review on brain repair.
BDNF is the star behind:
Two biggest triggers for addiction relapse??:
- BDNF levels!
Now…a very curious missing player with cold exposure.
Cold exposure and cortisol (stress)
We talked a lot about the "stress" of cold exposure.
This should be bad, right? After all, serotonin gets exhausted by stress.
Here's the fascinating piece….cold exposure brings the positive side of stress (adrenaline and dopamine) but not the negative (cortisol).
Cortisol is our primary stress hormone. Cortisol's effect on mental health is well-established but the duration and expectation matter.
- Short bursts of stress (exercise, cold exposure, etc) actually build resilience.
- Chronic stress or stress for which we can't control timing/duration is bad.
So…cold exposure (without hypothermia of course):
Norepinephrine increases in response to winter swimming, but no changes can be seen in plasma epinephrine or cortisol
That's a great review by the way.
This is called "eustress". Good stress (like exercise). By constantly priming this autonomic system, you're building resilience as well.
Let's turn to our favorite subject…steroidal hormones.
Cold exposure and steroidal hormones
In our rewriting your mental health past, we focused on two elements:
- Loss of steroidal hormones (estradiol, progesterone, testosterone)
- Editing the "mark-up" from prior trauma, infection, and stress from the immune system
People…this is IT for mental health!
- Estrogen and Testosterone are powerful drivers of serotonin and repair/replenishment
- Progesterone supports GABA for sleep, mental health, etc and calms immune function
Check out the reviews on each as they directly drive mental health.
Too bad Progesterone and Testosterone drop around 1% from age 20 and Estrogen goes off a cliff late 40s for women.
We took a look at rapamycin for longevity (more at our health hacks page) but there's a downside there we didn't like.
A drop in steroidal hormones. Makes sense…in times of simulated famine, not a great time to reproduce!
This may be cold exposure's secret weapon!
It can actually significantly increase steroidal hormones across the entire gamut…even LH (luteinizing hormone) which drops when you supplement with HRT as a pushback.
There's a good walkthrough here:
We need better research.
The timing matters (cold after and not before exercise is best).
What on earth is going on here? We mentioned how famine was bad for steroids…why would the perceived "danger" of cold have the opposite effect?
There's a fascinating interplay between brown fat and steroidal hormones.
In sum, Ucp-1 potentiation in BAT after cold stress is associated with early Ngf-response in the same tissue and trophic action in bone and testis.
Trophic means pro-growth. More activity.
LH is the primary "initiator" of steroidal hormone production in the gonads. The signal to make more (estradiol, testosterone).
Why would nature tie "cold" to steroidal hormones aside from the growth/repair side (similar to BDNF)?
There's actually a fascinating "annual" cycle for steroids. They peak late fall when the temperature drops. The evolutionary "goal" is to have babies late summer and the 3rd trimester (key for brain development, etc) during summer when times are good.
Viruses peak during the winter (their shell literally melts with cold weather) so best to avoid all this when expecting towards the final 3rd of pregnancy.
Either way, there's an ancient connection between temperature and steroids.
One we can ride back into good mental health.
Look at the reviews to really see how important they are:
Let's really zero in on the brain inflammation piece since it's front and center with mental health.
Cold exposure and brain inflammation
We touched on this above but let's dive in since the immune system is the future of mental health.
Since brown fat is the key driver of activity from cold exposure, let's start there.
It turns out that brown fat is incredibly anti-inflammatory while white fat can be very inflammatory. Systemically!
In fact, a study transferred brown fat to mice with autoimmune arthritis:
The proinflammatory cytokines in normal BAT-transplanted mice, such as IL-12, IL-17, IL-6, and tumor necrosis factor-α (TNF-α), tended to decrease.
Goodness..that's a laundry list of inflammatory agents.
In fact, it reflects a T1 setting in the immune system which is directly linked to every mental health issue out there.
See our neuroinflammation review to learn more.
In fact…our white fat may be part of this one-way inflammaging:
Adipose tissue constitutes the major source of cytokines, chemokines, and metabolically active mediators known as adipokines
Why this matters for mental health?
Higher levels of pro-inflammatory cytokines (TNF-α, IL-6 and IL-8) would be associated with more severe psychiatric symptoms
Wait…TNF-a and IL6 were directly reduced by brown fat (and therefore cold exposure).
Here's the fascinating piece (to us anyway)....early life stress can alter fat distribution later in life!
ES-exposed mice subjected to WSD exhibit a higher increase in adiposity when compared to controls, suggesting that ES exposure might result in a higher vulnerability to develop obesity in a moderate obesogenic environment.
ES is early life stress. WSD is western style diet (see our fats review).
More white fat = more inflammation = higher mental health risks!
Okay..lots of pathways and we could go on. Let's dive into key issues.
Cold exposure and anxiety
We have a massive review on anxiety.
At its heart, anxiety is failure of stress response (GABA, then serotonin, then anandamide) combined with brain areas leaning too hard on fear/vigilance.
We've covered many of these players above but how about a direct study?
After three weeks, a decrease of at least 50% from the baseline HDRS-17 scores in 34.6% of the study group and 2.9% of the control group and a decrease of at least 50% from the baseline HARS score in 46.2% of the study group and in none of the control group were noted.
HDRS is a standard depression test. HARS is a standard anxiety test.
50% drop! That's….well phenomenal.
That was after 3 weeks and the "remodeling" from cold exposure can take at least 30 days. That's how long it takes for receptors in the above pathways to come back online.
After all, DNA has to be turned back on! BDNF alone takes time since it's literally building new brain connections.
What about anxiety's partner in crime, depression?
Cold exposure and depression
Big review on depression here but it can best be seen as a disintegration of brain areas and activity from the assault of hormone loss, trauma, stress, infection, and other back actors.
Longer term, anxiety can cause depression from the sheer wear and tear.
New studies are starting to bare out the results of cold exposure:
cold hydrotherapy can relieve depressive symptoms rather effectively.
Look at the results of a standard mood test (POMS) of just one exposure!
The cold-water immersion group showed a significant decrease, with a large effect size, of 15 points from 51 to 36, compared to 2 points in the control group, 42 to 40.
This test measures both positive and negative mood qualities. Look at the results from one cold exposure:
Positive sub-scales increased significantly in the cold-water immersion group (Vigour by 1.1, and Esteem-Related Affect by 2.2 points) and negative sub-scales showed significant reductions (Tension by 2.5, Anger 1.25, Depression 2.1, Fatigue 2.2, and Confusion 2.8 points).
Goodness. Good luck getting that with SSRIs (see the problem with SSRIs).
Okay…a quick speed round of mental health
Cold exposure and other mental health issues
We need better research.
All mental health issues have shared attributes:
- Increased inflammation (hyperactive immune system)
- Poor stress response
- Metabolic dysregulation
- Early life stress, trauma, infection risk
We've seen above cold exposure affects each of these!
There's plenty of anecdotal info on various issues but we need more research. We expect it to follow suit with anxiety and depression and look forward to new data.
We've avoided one key area…maybe THE key area.
Let's go to the autonomic nervous system.
Cold exposure and acetylcholine
We're going to zero in on the vagus nerve, the hub between our two brains (gut and in the head).
One, is a key internal sensor, and the other, an external sensor.
Big review on supporting the vagus nerve but a primary role of it is to release acetylcholine.
That's the opposing force to adrenaline…it's our "calm and focused" player.
Seem relevant for mental health? It's a powerhouse for stress response. Just think what adrenaline feels like!! It's the opposite. But alert.
So…when we get into cold, adrenaline spikes (with dopamine) by default.
The body's a funny thing. If you spike any given pathway, it will actually exhaust a bit.
You see this with tolerance and every drug or most medications.
So what happens after the "cold shock" in this background system?
These results indicate that acute cold exposure activates cholinergic as well as nitrergic neurons in the gastric myenteric ganglia through vagal nicotinic pathways in conscious rats.
Right the ship! A spike in adrenaline will lead to a rebound increase in acetylcholine.
Just a head's up…this system is critical to ADHD, PTSD, anxiety, and more.
Okay…now get ready for this.
First….a basic definition:
Your parasympathetic nervous system is a network of nerves that relaxes your body after periods of stress or danger. It also helps run life-sustaining processes, like digestion, during times when you feel safe and relaxed.
Safe and relaxed indeed.
Cold exposure increased sympathetic activity, which was blunted after cold acclimation. The parasympathetic activity showed a minor increase in cold, which was enhanced after cold acclimation. In conclusion, cold habituation lowers sympathetic activation and causes a shift toward increased parasympathetic activity.
Let's translate that because it's too cool!
The increase in our "fight or flight" system during cold is followed by a "shift" to "rest and digest" afterwards.
THIS is the key to just about every mental health issue in a very powerful player (autonomic nervous system) that we have very little control over.
Panic attacks. Anxiety. Mania. ADHD. Pyschotic breaks.
We're slowly building resilience into our stress response system!
Check out other ways to support the vagus nerve but let's look at protection in the brain.
Cold exposure and neuroprotection
After a traumatic brain injury, hospitals will literally surround the skull with ice.
You may recognize some of these players from above:
Therapeutic hypothermia (TH) has been extensively studied at the experimental level, and has shown benefit against a variety mechanisms of brain injury, including reduction in metabolic activity, glutamate release, inflammation, production of reactive oxygen species, and mitochondrial cytochrome c release
- Inflammation. Check
- Oxidative Stress (oxygen species). Check
- Mitochondrial effects. Check
In fact, those are all present in every mental health issue you research.
We could get lost in the weeds but let's look at one exciting pathway.
FGF21. Goodness…a droid name?
No…it's a key player in breaking down amyloid plaques. Check our review of amyloid clot pathways.
FGF21 is a superstar in brain protection from everything we just listed!
FGF21 alleviates the nerve injury and maintains the mitochondrial stability. FGF21 relieves neurodegeneration by inhibiting inflammation and oxidant stress. FGF21 protects neurons by enhancing mitochondria function through AMPKα/AKT. FGF21 reduces neuroinflammation through inhibiting NF-κB pathway.
Goodness. Brain Inflammation. Mitochondrial dysfunction. Oxidative stress.
And cold exposure???
Cold exposure stimulates fibroblast growth factor 21 (FGF21) secretion in animals, enhancing the cold-induced thermogenesis (CIT) response through browning of white adipose tissue.
Makes sense…the body thinks its in peril…protect the vital cargo (brain).
Let's wrap up with the age-old (about 8 billion years actually) battle.
Cold exposure and the brain area battle for supremacy
Let's introduce the opponents.
In this corner, you have our old "reptilian" brain player. Evolutionarily ancient and pretty similar to our animal brethren.
This is where dopamine drives impulse and survivability.
The new player is the pre-frontal cortex, the kid on the block where humans picked the lucky ticket.
It's what makes you…YOU! Higher executive function. Planning. Thinking. The human stuff.
Here's the fascinating piece for mental health.
We have two brains.
- One is driven by primitive impulses including fear, anger, lust, and more.
- The other is a rational "push back" on the more "infantile" area
Mental health issues arise when the rational (adult) actor (pre-frontal cortex) is outgunned by our more child-like brain area (amgydala, striatum, etc).
As a simple example, anxiety occurs when the fear signal is too strong or the push back is outgunned.
The so-called "anxiety circuit".
In the case of depression, the prefrontal cortex just isn't running "hot" enough.
Why bring all this up with cold exposure?
Let's walk through it.
When you first feel the cold water, the "reptilian" brain is saying "Get the HELL out. NOW!!!"
Impulse. Impulse. Impulse. Pleasure seeking, pain avoiding.
Now…the only thing keeping you from darting out is…the prefrontal cortex.
You are "willing" yourself to stay in because you know you're buying future pleasure/calm/balance on credit!
However much pain you feel…will result in equal and even greater good feelings later.
That's rational. That's prefrontal cortex.
Everytime you do this, you're strengthening this area of the brain. You're building resilience.
It's very similar to mindful meditation where the action strengthens key pathways (hint hint…vagus nerve).
Working out is exercise for the body. Cold exposure is exercise for resilience.
- And metabolism
- And stress response
- And motivation
- And calm
- And energy
You get the picture. Work with your doctor. Listen to the Huberman podcast on various protocols to stay safe.
Be well. Cold exposure is a hack we have down here so take advantage of it.