PDF Summary:The Vagus Nerve Reset, by Anna Ferguson

Do you struggle with anxiety, stress, or difficulty connecting with others? The culprit might be your vagus nerve—a key communication pathway between your brain and body that influences everything from your heart rate to your immune response. In The Vagus Nerve Reset, Anna Ferguson explains how trauma and lifestyle factors can dysregulate your nervous system, keeping you stuck in states of fight, flight, or freeze.

Ferguson presents a three-phase program to recalibrate your vagus nerve and build resilience. You'll learn techniques like diaphragmatic breathing, vocal toning, and cold exposure to stimulate your vagus nerve directly. The guide also covers how to leverage social connections for nervous system regulation, establish trust in yourself and your body, and integrate supportive daily practices. Ferguson's approach combines practical exercises with insights into how your nervous system works, offering a path toward greater calm, emotional regulation, and well-being.

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Keeping records helps you view yourself objectively, which is essential for improving your life. You can monitor your moods subjectively by questioning how you feel, or objectively by using measurement scales to evaluate the intensity of your emotions. You can use a Worry Log to track your anxiety episodes and a Daily Mood Journal to reflect on your overall mood and anxiety levels.

Using Records to Test Your Anxious Thoughts

Therapists have long used record-keeping to help people with anxiety. For example, the workbook Mind Over Mood teaches people with anxiety to keep records of their thoughts, feelings, and behaviors. This approach is similar to Ferguson’s suggestion of using a Worry Log or Daily Mood Journal. The workbook’s authors argue that keeping records helps you test your anxious thoughts and beliefs. For example, if you believe that you’ll fail a test, you can record your thoughts and feelings before and after the test. This helps you see if your beliefs were accurate. If you did well on the test, you can use this information to challenge your anxious thoughts in the future.

Ferguson also highlights that cultivating trust in yourself is essential for emotional well-being. Trusting yourself is the basis that underpins everything else in your life. It lets you form a deep bond with yourself and expand it into your surroundings. This skill is vital to develop, and it might require time. As you keep exploring yourself and your experiences, you’ll discover new approaches to trusting yourself more profoundly. The aim is progress, not perfection. When you have self-trust, you recognize your strengths and capacity to overcome whatever challenges life presents. Having self-trust empowers you to take risks, choose your path, and follow your instincts.

(Shortform note: Ferguson’s advice to make self-trust the basis that underpins everything in your life and to follow your instincts when taking risks may not always be the best approach. In Thinking, Fast and Slow, Daniel Kahneman explains that our instincts are often unreliable due to cognitive biases. He argues that our brains are prone to systematic errors in judgment, such as overconfidence, loss aversion, and the availability heuristic. These biases can lead us to make poor decisions even when we feel certain about our choices. Kahneman’s research shows that trusting our instincts without critical thinking can result in predictable mistakes. Therefore, while self-trust is important, it should be balanced with an awareness of our cognitive limitations.)

This requires a commitment to self-honesty, even during difficult or troubling times. This marks the start of the effort. Developing self-trust is challenging and requires diligence, hard work, and patience. If you lack self-trust, it can make everything seem difficult. If you lack the confidence to trust that things will ultimately be okay, it’s hard to emotionally engage with other people. It's vital to have confidence in ourselves to accomplish this. When we're familiar with our thoughts and comfortable with our inner selves, we feel more secure in ourselves.

(Shortform note: When we’re honest with ourselves and familiar with our thoughts, we’re able to create a more coherent narrative about who we are. This narrative coherence helps us feel more secure in ourselves because it allows us to make sense of our experiences and emotions. When we avoid or deny our thoughts and feelings, our brains struggle to process and integrate them, leading to a fragmented sense of self. This fragmentation can trigger our brain’s alarm system, making it difficult to develop self-trust. By facing our thoughts and feelings honestly, we give our brains the information they need to create a stable sense of self, which in turn quiets the alarm system and allows self-trust to grow.)

Feeling secure enables us to be more vulnerable with others, which helps them reciprocate our affection. To develop self-trust, you need to be aware of yourself, reflect, and have self-compassion. This process includes recognizing and embracing what you’re good at and where you fall short, and gaining insight from previous experiences. Learning requires risk-taking and making errors. Engaging in these activities increases your confidence and resilience. Ferguson notes that engaging with this book and gaining insight into your body's nerves is risky in a way—you're exploring uncharted territory, which might feel intimidating. By gaining a deeper insight into your own nature and your relationships, you strengthen your self-trust. When you understand the causes of your happiness, sadness, anger, or fear, it becomes easier to care for yourself and make beneficial choices over time.

(Shortform note: Ferguson’s ideas about self-trust echo those of humanistic psychologist Carl Rogers, who argued that a strong therapeutic relationship can help people develop self-trust. In On Becoming a Person, Rogers explains that when a therapist accepts a client unconditionally, the client feels safe enough to explore their true self. This honest self-exploration, Rogers believed, helps people learn to trust their own experiences and feelings. He argued that self-trust grows when people take risks, make mistakes, and learn from them. Rogers’s ideas, developed in the 1950s and 1960s, laid the groundwork for later theories about self-trust and personal growth.)

Self-confidence is significantly hindered by self-doubt, perfectionism, and shame. When you're overwhelmed by these emotions, it's difficult to believe in your capabilities and yourself. You may feel that others are superior or that you don't deserve what you want. You might think you don't measure up in intelligence, attractiveness, or overall worth—and that can lead you to feel you can't follow or trust your instincts. When you doubt your abilities, it's challenging to act or experiment with new things. You sense you've failed before you even start. This type of doubt urges you to back out of social plans, fearing friends will see through your façade and perceive you as a phony.

(Shortform note: In addition to self-doubt, perfectionism, and shame, another factor that can undermine self-confidence is long-term exposure to prejudice and stereotype-based expectations. In Whistling Vivaldi, Claude M. Steele explains that when people are exposed to negative stereotypes about their social group, they learn to expect devaluation and extra scrutiny in important settings. This ongoing experience of stereotype threat gradually wears down their sense of competence and belonging, constricts what they see as possible for themselves, and leads them to underperform relative to their actual abilities. Even people with strong abilities and past successes can have their self-confidence eroded by persistent exposure to prejudice.)

Shame can be just as crippling as self-doubt. It's the sense that you're insufficient for others or will make them uneasy because of how they perceive your shortcomings. Shame convinces you that you're defective, valueless, and unlovable—and that people wouldn't want to be around you if they knew what was truly happening inside you.

(Shortform note: In their book on shame, Tangney and Dearing cite numerous studies showing that people who habitually view themselves as fundamentally defective are more likely to suffer from depression, anxiety, and other psychological problems. This supports the idea that shame can be crippling. When you believe you're fundamentally flawed, you may feel hopeless about your ability to change, which can lead to a sense of helplessness and despair.)

Perfectionism, which involves imposing unattainable goals on yourself and then punishing yourself for not reaching them, is a form of self-sabotage. Feeling trapped in perfectionism might seem inescapable. It's easy to become trapped in comparisons to others, leading you to feel that you never measure up and undermining your belief in your skills. Experiencing perfectionism, shame, and self-doubt occasionally is normal for humans, but if they're your automatic reaction to difficult times, it’s a strong sign you lack complete self-trust, including in your body and inherent wisdom.

(Shortform note: While perfectionism, shame, and self-doubt can be signs of low self-trust, there are situations where they might not indicate a lack of self-trust. In The Geography of Thought, Richard E. Nisbett explains that in many East Asian cultures, self-criticism and modesty are valued social norms. People in these cultures often downplay their abilities and focus on their shortcomings as a way to maintain social harmony and show a commitment to self-improvement. In these contexts, frequent feelings of shame or self-doubt might reflect cultural values rather than a fundamental mistrust of oneself.)

Reclaiming yourself begins with sensation: becoming aware of your body, emotions that previously couldn’t flow through you, and the feeling of “this is me, this is my physical form, this is my home.” But reestablishing that sensory awareness necessitates some trust. Trust is described as having a strong confidence in the dependability, honesty, or capabilities of a person or entity. If it's been a while since you've connected with your body, you might be skeptical of its sensations and feelings. If you've suppressed or avoided certain feelings, you won't feel assured that you can fully experience them.

(Shortform note: For some people, the idea of “this is me, this is my physical form, this is my home” can be overwhelming. In The Body Keeps the Score, Bessel van der Kolk explains that for many traumatized people, their own physical sensations feel like enemies rather than signals. When they start to notice what is happening inside their bodies, the rising tides of heartbeat, breath, tightness, and agitation can instantly transport them back into the terror and helplessness of the original trauma. This is why work with bodily awareness has to be introduced very gradually, in tolerable doses, and within a relationship and environment that provide a strong sense of safety and support.)

Ferguson notes that you have to reclaim confidence in yourself, your skills, and your capability to manage everything about you, and you should also start to restore your confidence in others, so that you can reclaim yourself as you’re designed and have the potential to be. Trust is possible only with a degree or feeling of familiarity. Recognizing familiar elements often provides reassurance or self-confidence. Essentially, trust develops from feeling secure.

(Shortform note: Ferguson’s assertion that trust is only possible with familiarity may not be universally true. In Trust: The Social Virtues and the Creation of Prosperity, Francis Fukuyama explores how trust operates in different societies and argues that high-trust societies are characterized by a willingness to trust strangers and institutions without prior familiarity. He explains that in such societies, people often extend trust to unknown individuals and abstract systems because they expect shared norms to guide behavior, even in the absence of personal contact.)

When you engage with your body by noticing its sensations, what emotions they provoke, and your internal dialogues, you can start dismantling the shame that's limiting you. When you begin engaging with your body and realize the many ways it symbolizes your inner world, you can start healing past wounds, establishing a new basis, and developing profound self-trust. As you start to have confidence in yourself, it extends to help you trust others, letting you foster positive and respectful relationships. Humans are inherently social, driving us to build and deepen bonds with people and our surroundings. This force is strong and helps you as well as those nearby. By developing self-trust, you'll also find it easier to have confidence in others, which can enhance your sense of stability beyond your own being.

(Shortform note: While focusing on your bodily sensations and the emotions they evoke can be healing, it can also be destabilizing for some people. For those with significant unresolved trauma, concentrating on internal feelings can sometimes reignite distress rather than reduce it. This is because the body stores traumatic memories, and intense focus on bodily sensations can trigger these memories, leading to increased anxiety or emotional overwhelm. For example, someone with a history of physical abuse might find that paying close attention to muscle tension or heart rate brings back vivid memories of past trauma, causing panic attacks or dissociation.)

Having confidence in yourself starts you on the path to taking back your existence, and it’s the initial move toward regaining your power and self-worth. By developing self-trust, you can start building a life that aligns with your core identity and feels genuine.

(Shortform note: While self-confidence is generally seen as a positive trait, it can become problematic when it turns into overconfidence or narcissism. Overconfidence can lead to poor decision-making, as individuals may overestimate their abilities and underestimate risks. Narcissistic self-confidence can damage relationships, as it often involves a lack of empathy and an inflated sense of self-importance. This can lead to social isolation and hinder personal growth, as individuals may become resistant to feedback and self-improvement.)

Core Practices & Techniques

Ferguson suggests exploring somatic practices to attune to your body. These are body-centered techniques that employ physicality to process and recover from emotional trauma. They consist of physical activity, physical contact, and bodily mindfulness. Somatic practices help you increase your awareness of your body’s sensations and emotions, ease bodily tension, and encourage emotional healing. They enhance your sense of being rooted in your body, allowing you to better manage your feelings and ideas.

Somatic practices also help you release stress and anxiety, enabling you to handle, release, and feel challenging emotions without using words. They help you cultivate more self-awareness and a heightened feeling of security. Try gentle movement practices like gentle side-to-side movements or rhythmic back-and-forth motions, rejuvenating yoga poses like child’s pose or savasana, or somatic stretching exercises like standing awareness.

The Role of Somatic Practices in Trauma Therapy

Ferguson’s somatic practices are part of a trauma-therapy tradition that Bessel van der Kolk discusses in The Body Keeps the Score. He argues that traumatic stress is not, at its core, a disorder of cognition or belief but a disruption of the organism’s physiological self-regulation, in which the autonomic nervous system becomes chronically stuck in states of fight, flight, or freeze. He explains that meaningful recovery therefore requires bottom-up interventions that directly engage bodily sensations and the neural circuits that regulate arousal and safety, rather than relying solely on insight-oriented, verbal therapies. This perspective challenges the traditional view that trauma is primarily a psychological phenomenon that can be resolved through cognitive processing and reframing. Instead, it suggests that trauma is fundamentally a physiological condition that must be addressed through embodied practices that restore the body’s capacity for self-regulation and safety.

Ferguson also highlights how crucial it is to integrate different activities into your everyday life. Incorporating new practices is the key phase in your path to healing, though it's often ignored. To integrate, you'll need two essential elements: doing it repeatedly and maintaining regularity. Develop a practical plan incorporating the methods you find most meaningful.

(Shortform note: To make this practical plan a reality, try using an if-then formula. For example, “If I finish my morning coffee, then I immediately do two minutes of my chosen activity.” This approach helps you establish a consistent routine by linking your new activity to an existing habit, making it easier to remember and maintain.)

Let’s explore some direct vagal stimulation techniques, along with social interactions and co-regulation practices.

Direct Vagal Stimulation Techniques

Ferguson highlights that diaphragmatic breathing can improve the vagus nerve's tone. This method involves slow, rhythmic breathing using the diaphragm. Diaphragmatic breathing causes your stomach to expand with inhalation and contract with exhalation. This can improve vagal tone and raise your HRV. The best breath frequency for your body and nervous system is 6–10 breaths each minute. Breathing through your nose is also crucial for enhancing how you breathe. Resonant breath training is a method that decreases the speed of your breathing to about six breaths a minute, maximizing your HRV.

(Shortform note: While Ferguson suggests a range of 6–10 breaths per minute, she doesn’t explain how to determine the best rate for you. In an academic paper, researchers suggest a method for finding your optimal breathing rate. First, try breathing at a rate of six breaths per minute for a few minutes. Then, try breathing at a rate of 5.5 breaths per minute, and so on, until you reach a rate of 4.5 breaths per minute. While doing this, observe your heart rate pattern. The rate that produces the largest, smoothest oscillations in your heart rate pattern is your optimal breathing rate.)

You may experience calmness and relaxation in this state. Engaging in resonant breathing periodically during the day can help you reduce your base stress levels and start to enhance your vagal tone. To try diaphragmatic breathing, start by figuring out how to engage your diaphragm and breathe with it. Put a hand on your chest and one on your stomach. Inhale through your nose and imagine your belly expanding like a balloon. To activate your diaphragm, try placing an item on your stomach, like a book or warm pack. When you exhale, your stomach will shrink and tighten. Keep your chest still. Practice engaging the diaphragm and expanding your stomach as you inhale for five minutes a day for a week.

(Shortform note: A review of controlled studies by Paul M. Lehrer, Evgeny Vaschillo, and Bronya Vaschillo found that slow, paced breathing at an individual’s cardiovascular resonance frequency, when practiced regularly over periods ranging from one to several weeks, produces large increases in heart rate variability amplitude and baroreflex gain and has repeatedly been associated in controlled studies with clinically meaningful reductions in anxiety, depression, and other stress-related symptoms, indicating that this form of respiratory training can strengthen vagal regulation of the heart and improve emotional self-regulation. This supports the idea that short, regular practice of resonance-frequency diaphragmatic breathing can lower baseline stress levels and improve vagal tone, as described in this passage.)

Then, begin adjusting your breathing speed. A pace of six breaths each minute generally involves inhaling for five seconds and exhaling for five seconds, or inhaling for four seconds and exhaling for six. Practice reducing how quickly you breathe for a few minutes each day.

(Shortform note: In Trauma-Sensitive Mindfulness, David A. Treleaven notes that for some trauma survivors, the breath is not a neutral or soothing place to focus attention. For those who have experienced suffocation, medical trauma, or panic attacks, concentrating on the breath can actually heighten distress.)

Ferguson also notes that vocal toning and music can stimulate the vagus nerve. Vocal toning involves adjusting the loudness, timbre, and intonation of your vocal sounds. Music helps unite us. The vagus nerve supplies your vocal cord muscles, so your voice can impact and improve vagal tone. Music can assist in the regulation of your nervous processes. Hearing music that's calming, rhythmic, and unhurried can lower your pulse, the force of your blood flow, and your breathing speed. Singing and humming stimulate the vagus and enhance heart rate variability.

(Shortform note: For people with misophonia, vocal toning and music may not be helpful. Misophonia is a condition in which certain sounds trigger intense irritation and physiological stress responses. For example, a person with misophonia might find the sound of someone humming or singing to be unbearable, even if the music is calming and rhythmic. This can lead to increased heart rate, blood pressure, and breathing rate, which are the opposite of the effects described above.)

To try vocal toning, talk like you're speaking to another person. Vary the loudness, pitch, and sound of your voice, ranging from booming to hushed, song-like to monotone. This will help you become aware of how you speak to others and give you more chances to consciously alter the tone, rhythm, and tempo of your voice. To practice breath and vocal toning, sit comfortably, keeping your back straight and shoulders loose. Shut your eyes, or pick a point on the floor before you, letting your gaze soften and your vision relax.

(Shortform note: These instructions are reminiscent of polyvagal-informed voicework in trauma therapy, where clients are encouraged to explore the musical qualities of their speech as a way to shift autonomic state. In The Polyvagal Theory in Therapy, Deb Dana describes how the autonomic nervous system is continuously listening to the music of the human voice—its prosody, rhythm, and warmth—as one of the primary cues of safety or threat. By bringing mindful attention to how we sound in conversation and experimenting with changing the musical qualities of our speech in the presence of another person, we can engage the social engagement system and invite more ventral vagal activation.)

Start by decelerating your breath, inhaling nasally for five counts and exhaling through pursed lips for seven counts. Repeat, breathing slowly for ten breaths. For the following breath, inhale deeply and hold at the peak. As you inhale deeply and pause, blow your cheeks out while keeping your lips pressed tightly closed so that air can't escape. As your cheeks are puffed out, start humming at a high pitch, similar to a bee. While humming, air will automatically exit your nostrils. Keep humming while your cheeks are puffed out until you've fully exhaled. Release any tightness in your face and cheeks, then breathe naturally three times. Repeat this series of steps ten times. To use music to stimulate your vagus nerve, look into different types, performers, and groups to discover those that stir feelings and sensations. Create playlists that guide you through varied nervous system states.

Breathwork and Humming

In their 2017 book The Humming Effect, Jonathan and Andi Goldman describe a similar routine that combines slow nasal breathing with humming. They also discuss the therapeutic use of recorded sounds to influence physiological and emotional states. The Goldmans’ routine begins with five slow nasal breaths, inhaling for five counts and exhaling for five counts. On the sixth breath, inhale deeply and hold for a moment. Then, with your mouth closed, hum a single note for as long as possible. Repeat this cycle five times, then breathe normally for a minute. They recommend practicing this routine daily for several weeks to experience its full benefits. The Goldmans also emphasize the importance of selecting music and sounds that resonate with you personally. They suggest experimenting with different genres, tempos, and instruments to find what best supports your desired state. For example, you might choose calming nature sounds for relaxation or upbeat rhythms for energy.

Social Engagement & Co-Regulation Practices

Ferguson explains that the vagus nerve plays a key role in social engagement and co-regulation. The social engagement mechanism is the part of the nervous system that enables us to connect with others, while co-regulation is the process of using another person’s regulated nervous system to help us regulate our own.

The primary route for the functioning of social engagement is the vagus nerve. It lets us feel secure and linked to others, which in turn helps us regulate our own nervous system. The vagal nerve additionally contributes to co-regulation. When we are around someone who is calm and regulated, our own nervous system can “borrow” from their state, helping us to feel more calm and regulated ourselves.

The Social Nature of the Brain

The idea that our nervous systems are shaped by our relationships is a key theme in the work of neuroscientist Louis Cozolino. In The Neuroscience of Human Relationships, Cozolino argues that the brain is a social organ, shaped and regulated by interpersonal experience. He explains that from birth, our neural systems are organized within an attachment matrix, and that close relationships operate as an external scaffolding for our nervous systems. This means that our brains are not isolated organs, but are instead part of a larger network of social brains that regulate and support each other. Cozolino’s work suggests that our nervous systems are not just individual systems, but are part of a larger social network that helps us regulate our emotions and behaviors.

Ferguson adds that social bonds are essential for mental wellness and general health. These are beneficial engagements with others and our environment. Humans are biologically wired to be social beings. As a species, we've survived because of our capacity to cooperate and form social bonds. We’ve developed a "social brain" that mainly works to maintain our connections with people.

(Shortform note: The “social brain” is a term used in social neuroscience to refer to the brain regions that are more active when we perceive or think about other people than when we do non-social tasks. These regions include the amygdala, the temporal lobes, and the prefrontal cortex.)

The vagal nerve serves as the biological mechanism that makes connection inevitable. When the vagal nerve is stimulated, the ventral vagal network is engaged—also known as the system responsible for social engagement. When this social connection network is active, we feel secure and bonded with others, which increases our likelihood of expressing proper facial signals—like smiling—and improves our ability to speak and listen fluently. People who have social bonds and positive, reciprocal, respectful relationships with trustworthy individuals often experience improved mental health and well-being relative to people who lack these connections. Social relationships are vital to recovery, especially for feeling included and growing your support system.

(Shortform note: The vagal nerve may not make connection inevitable. In the US, 22% of adults report feeling lonely or socially isolated, and 25% of adults over 65 are considered socially isolated. Loneliness is a subjective feeling of being alone, regardless of the amount of social contact, while social isolation is an objective lack of social connections. Both can have serious health consequences, including increased risk of heart disease, stroke, dementia, and premature death. Chronic loneliness can last for years, suggesting that the vagal nerve doesn’t guarantee social connection, even though we all share the same vagal anatomy.)

However, people dealing with mental health problems frequently struggle more with forming connections, particularly those who've been through trauma. Studies indicate that those with traumatic experiences might struggle to trust people or feel secure in intimate relationships. This may hinder developing robust social ties and gaining the advantages of social support.

(Shortform note: Another factor that may make it difficult for people with mental health problems and trauma to form social connections is the stigma attached to these issues. People with mental health problems and trauma may feel that others will judge them or treat them differently if they reveal their struggles. This fear of stigma can lead to social withdrawal and isolation, making it even harder to build the supportive relationships that are so important for mental health.)

Supporting & Detracting Factors

Ferguson explains that natural light exposure supports the vagus nerve and the nervous system. It assists in the regulation of cortisol and melatonin production, supporting healthy circadian cycles. Circadian rhythms resemble an internal schedule present in every cell, including those in your brain. This timetable establishes the cadence for processes like slumber, thermal regulation, metabolism, and emotional state. Stress and heightened cortisol can cause disruptions in circadian rhythms. This may lead to fluctuations in your 24-hour internal sleep-wake rhythm. Bright daylight can have an indirect effect on mood and sleep by influencing the availability of chemicals like serotonin, which helps control emotions.

(Shortform note: While natural light exposure is generally beneficial for regulating circadian rhythms, cortisol, and melatonin, there are exceptions. For example, people with certain types of blindness may not experience these benefits. The authors explain that in people with total blindness, the eyes can no longer send light signals to the brain’s circadian clock. As a result, their internal rhythms for sleep, hormone production, and body temperature may become disconnected from the 24-hour day-night cycle. This means that their cortisol and melatonin levels may not follow the typical daily patterns, and their vagus nerve activity may also become desynchronized from the natural light-dark cycle.)

It also aligns and steadies the body's innate rhythms by matching them to indicators like daybreak and nightfall. Sunlight is a freely available, convenient aid for promoting a regular sleep cycle and good sleep habits, and for balancing mood. It provides essential signals to help recalibrate your circadian rhythm, particularly at the start of the day. Getting sunlight early in the day helps your system align again with the internal schedule that's hardwired into your cells. Light plays a vital role in signaling your body's sleep cycle. Daylight exposure helps regulate when you should go to sleep and wake up. For optimal benefit, be outside in the sunlight early in the day.

(Shortform note: Light exposure in the morning helps your system align with its internal schedule because light detected by your eyes is sent directly to a tiny region in your brain called the suprachiasmatic nucleus (SCN). The SCN acts as your body's master clock, adjusting the timing of biological processes throughout your body. This direct connection between your eyes and your brain's clock is why light exposure is so effective at resetting your internal rhythms.)

Ideally, within an hour of waking up, aim to get 20 minutes of direct sunlight. You'll get the most benefit from natural light when you're exposed directly to it—without any sunglasses, hats, or light-filtering windows. You can benefit from sunlight even on cloudy or gray days. Natural illumination is accessible even in cold, overcast, or rainy conditions, effectively keeping your internal clock in balance. Simply face toward the sunlight.

The Risks of Chronic Sun Exposure

While 20 minutes of direct sunlight exposure may not seem like much, over the course of a year, this adds up to over 120 hours of unprotected sun exposure. Over a lifetime, this cumulative exposure can significantly increase your risk of skin cancer and eye damage. According to Dermatology by Jean L. Bolognia, Julie V. Schaffer, and Lorenzo Cerroni, chronic, repeated exposure of uncovered skin and unprotected eyes to solar ultraviolet radiation, even in relatively short daily intervals, is the principal environmental factor driving photoaging and photocarcinogenesis. Modern dermatologic practice emphasizes rigorous photoprotection—regular use of broad-spectrum sunscreen, protective clothing and wide-brimmed hats, and UV-blocking eyewear—as a key strategy to reduce the cumulative risk of actinic keratoses, basal cell carcinoma, squamous cell carcinoma, melanoma, and UV-induced ocular damage over a lifetime.

Ferguson also notes that cold exposure can stimulate the vagal nerve and improve overall health. It can decrease sympathetic activation and enhance parasympathetic nervous system activity. It can also enhance cardiovascular and respiratory health, bolster the immune system, reduce inflammation, and regulate the stress response. To practice cold exposure, you could shower in cold water, take a cold plunge, dunk your head in cold water, use a cold compress on your neck and upper torso, or be outdoors in cold weather.

(Shortform note: In What Doesn’t Kill Us, Scott Carney describes a laboratory experiment in which volunteers who had trained in Wim Hof’s combination of breathing exercises and regular cold exposure produced a dramatic spike in epinephrine (adrenaline) right before they were injected with an endotoxin. As a result, they showed markedly fewer flu-like symptoms and significantly lower levels of pro-inflammatory cytokines than untrained volunteers.)