Can The Smile Be The Answer? A September Reminder From Science And Dentistry

"Sometimes your joy is the source of your smile, but sometimes your smile can be the source of your joy." — Thich Nhat Hanh

The End of Summer, and a Question Worth Asking

September has a particular quality to it. The light shifts. The pace picks up. The ease of summer — the longer evenings, the slower mornings, the spontaneous laughter of people who have temporarily set their obligations down — begins to give way to something more structured and, for many people, more pressured.

I notice it in the clinic. Patients come back from August looking rested, and by late September that quality has often faded. The jaw is tighter. The grinding has returned. The stress that was briefly interrupted by a vacation or a change of scenery has resumed its conversation with the body.

Which is exactly why September feels like the right moment to talk about smiling — not as a platitude, not as advice, but as a genuine, peer-reviewed, neurochemically documented phenomenon that most people have never been told the full story about, and that has more to do with health than almost anyone realizes.

The Direction Goes Both Ways

Most of us understand smiling as an output — something happens, something good or funny or warm, and the face responds. The smile is the signal that joy has arrived.

What the science has established, with increasing rigor over the past several decades, is that the relationship runs in both directions. The face is not just reporting an emotional state. It is actively participating in creating one, through a feedback loop between the facial muscles and the brain's emotional processing centers that operates largely below conscious awareness.

This is the facial feedback hypothesis, and while it has been debated and refined since Charles Darwin first wrote about the relationship between expression and emotion in 1872, a landmark study published in Nature Human Behavior — involving 3,878 participants across 19 countries — confirmed it with a scale and rigor that earlier research could not achieve. When people were guided to engage the muscles of a smile, even without an explicit emotional trigger, they reported measurable increases in positive affect. The physical expression preceded and influenced the emotional experience rather than merely reflecting it.

The mechanism becomes less surprising once you understand the anatomy. When the zygomatic major muscle — the one that pulls the corners of the mouth upward — contracts, it sends a signal to the brain's emotional processing centers. The amygdala receives that signal. The hypothalamus responds. And a cascade of neurochemicals begins: dopamine, serotonin, endorphins, and neuropeptides — the same compounds that antidepressants, pain medications, and stress-reduction interventions work to influence — are released not because something external has triggered happiness, but because the face has sent the brain a message about how things are going, and the brain has responded accordingly.

Perhaps the most compelling evidence for this bidirectional relationship comes not from a laboratory but from a movement that began in a Mumbai park in 1995. Dr. Madan Kataria, an Indian physician who had been researching the documented health benefits of laughter for a medical journal, gathered five people and began what would become Laughter Yoga — a practice that combines simulated laughter exercises with yogic breathing, requiring no jokes, no humor, and no particular reason to laugh. The founding insight was both simple and radical: the body cannot distinguish between genuine and simulated laughter. When the muscles of laughter are engaged, the neurochemical cascade follows regardless of whether anything is actually funny. What begins as a deliberate, slightly absurd act of collective fake-laughing typically becomes, within minutes, genuine laughter — because the body's own chemistry takes over. Today, Laughter Yoga has spread to more than 100 countries, with over 16,000 clubs worldwide. Research on its practitioners has documented reductions in cortisol, improvements in mood and energy levels, and stronger social bonds — all from an activity that begins as a performance and becomes, through the body's own intelligence, something real.

A parallel tradition has emerged in Japan, where the post-pandemic period revealed something quietly striking: years of mask-wearing had left many people genuinely uncertain how to smile. Keiko Kawano, a former radio personality who founded Egaoiku — which translates directly as "smile education" — had been teaching smile training since 2017, but demand multiplied fourfold after masks came off. Her programs, which teach students to consciously engage the facial muscles associated with genuine expression, have reached thousands of people across Japan, from corporate employees to elderly residents of senior care centers. Participants consistently report not just improved social confidence but a shift in internal state — a more positive general outlook that follows from the deliberate, repeated practice of expression. The Japanese concept of egao — literally "smiling face" — carries within it the understanding that expression and inner state are not fixed in a one-way relationship. You can cultivate one by attending to the other.

What all of this points to is a practical truth that the science supports: a smile chosen in the absence of obvious reason is not a performance or a pretense. It is an intervention — a direct signal sent from the face to the brain, initiating a neurochemical response that would otherwise require an external trigger. The direction goes both ways, and the most interesting discovery may be that you do not need to wait for life to hand you a reason to smile. You can simply begin, and let the biology follow.

What Happens in the Body When You Smile

The neurochemical cascade that follows a genuine smile — what researchers call a Duchenne smile, named after the 19th century French neurologist Guillaume Duchenne who first identified it — is not a minor or incidental event. It is a measurable, systemic biological response with downstream effects on multiple organ systems simultaneously.

Cortisol, the body's primary stress hormone, falls. A study at the University of Kansas found that smiling during stressful situations — even when the smile was held artificially, using chopsticks positioned to engage the facial muscles — produced significantly lower heart rate recovery times and lower cortisol responses than neutral or negative expressions. The body responded to the shape of the face regardless of whether the emotion behind it was genuine. Chronically elevated cortisol is implicated in periodontal disease, immune suppression, disrupted sleep, cardiovascular disease, and accelerated cellular aging, which makes anything that reliably reduces it clinically meaningful.

Blood pressure also responds. The endorphin release that accompanies smiling acts on opioid receptors throughout the body, reducing the perception of pain and lowering vascular tone. Patients who smile more frequently have been found to have consistently lower resting blood pressure in multiple independent studies, a finding that is particularly relevant given that hypertension remains one of the most undertreated chronic conditions in the developed world.

The immune system is affected as well. Research has shown that positive emotional states linked to smiling increase white blood cell activity, specifically natural killer cell production — the cells responsible for identifying and destroying pathogens and abnormal cells. The relationship between mood and immune function is now a well-established field in psychoneuroimmunology, and smiling sits at one of its most accessible and cost-free entry points.

Beyond the individual body, smiling operates through an entirely different mechanism in social environments. The brain contains a mirror neuron system — a network of cells that fires both when you perform an action and when you observe someone else performing it. When you see a genuine smile, your mirror neurons activate the muscles of your own face within a few hundred milliseconds, before conscious thought has any opportunity to intervene. Smiling is contagious not as a metaphor but as a neurological fact, and the trust, warmth, and social connection that follow from that involuntary mimicry have their own downstream health consequences. People who report higher social trust have been found to have higher subjective wellbeing, lower rates of anxiety and depression, and in multiple large studies, longer lives.

The Duchenne Distinction

Guillaume Duchenne identified in the 1860s that a genuine smile engages two muscles simultaneously: the zygomatic major, which raises the corners of the mouth, and the orbicularis oculi, which creates the characteristic crinkle around the eyes. A social smile — the polite, performed version most of us produce on command — typically engages only the first. The second is much harder to fake because the orbicularis oculi is largely involuntary, responding to genuine positive emotion in a way that most people cannot consciously replicate on demand.

The brain distinguishes between these two expressions at a neurological level, producing a stronger neurochemical response, a more powerful mirror neuron activation in observers, and a more durable shift in mood in response to the genuine version. A 2019 study published in Neuropsychologia found that genuine smiles activate brain regions associated with pain reduction more effectively than posed ones.

This does not mean that an intentional, performed smile has no value — the Stanford-led study of nearly 4,000 participants demonstrated that even deliberate facial expressions produce measurable mood shifts. What it does mean is that the conditions in which genuine smiles arise naturally — safety, comfort, authentic connection, the absence of pain or self-consciousness — are worth attending to as health variables in their own right, not as nice-to-haves but as contributors to the neurochemical environment in which the body either thrives or struggles.

What Smiling Does for the Mind

The effects of smiling on the body are well-documented. Its effects on cognitive function are less widely known and, in some ways, more surprising.

Research published in peer-reviewed literature has found that the act of smiling — through the same facial feedback mechanism that lifts mood — also improves working memory for positive emotional content, enhances cognitive flexibility, and supports the kind of divergent thinking that underlies creativity and problem-solving. The connection is not incidental. Positive affect, which smiling helps generate, has been shown across multiple studies to broaden the scope of attention and increase the brain's capacity for what psychologists call associative thinking — the ability to draw unexpected connections between ideas. Under stress, the brain narrows its focus. Under positive emotion, it opens.

There is also a growing body of evidence linking the neurochemical environment that smiling creates to reduced anxiety in social situations and to greater resilience against depression. A study conducted in Germany in 1988, and replicated in 2019, found that facial feedback effects from smiling increased resilience to depression by 28% — a finding that has direct implications for how we understand the relationship between expression and mental health over time.

The Body in Motion — and the Hunter-Gatherer Gap

One of the more unexpected findings in the research on smiling involves physical performance. A study from University College London found that athletes who smiled during exercise improved their endurance by 12% compared to those who maintained neutral or frowning expressions. The mechanism is consistent with everything else the science tells us — smiling reduces the perception of effort, lowers cortisol, and allows the body to sustain output that feels harder than it is.

There is also a broader cultural observation worth sitting with. Adults in modern societies smile, on average, approximately 400 times less per day than people in hunter-gatherer communities. Children smile up to 400 times a day. The average adult smiles between 20 and 40 times. The gap between those numbers is not merely a curiosity — given everything the research has established about what smiling does to the immune system, the cardiovascular system, the neurochemical environment, and the quality of social bonds, it is a gap with measurable health consequences.

The Skin, Oxytocin, and an Unexpected Anti-Aging Connection

Genuine smiling — particularly in the context of authentic social connection — triggers the release of oxytocin, the neuropeptide most commonly associated with bonding, trust, and maternal behavior. What is less commonly known is that oxytocin has documented effects on the skin itself. Research published in Dermatology Times in 2026, drawing on clinical and preclinical evidence, identified that both oxytocin and its carrier protein are synthesized in keratinocytes — the primary cells of the outer skin layer — and that oxytocin binding to fibroblast receptors suppresses a senescence-associated secretory phenotype: in plain terms, it reduces the inflammatory signaling that accelerates skin aging.

This is not an argument that smiling is a skincare regimen. It is an observation that the neurochemical cascade set in motion by genuine positive expression and authentic social connection reaches further into the biology of the body than most people have been told — including into the tissues that are most visibly associated with aging and vitality.

A Word About Teeth

I will say the obvious thing briefly and let the science speak for the rest: patients who feel comfortable with their smile tend to smile more freely. And patients who smile more freely produce more dopamine, more serotonin, more endorphins. They experience less chronic stress. Their immune systems are more active. Their social bonds are stronger. Their blood pressure tends to be lower.

As your dentist, I never concentrate on purely cosmetic outline. It is the removal of barriers — pain, self-consciousness, decay, disease, past trauma in the dental office — that stand between a person and the full, uninhibited expression of something the body already knows how to do and benefits enormously from doing. A healthy mouth gives the face that permission, and what follows from that permission, the science has documented in considerable detail.

September, and the One Thing That Costs Nothing

The season is turning, and the particular ease that summer offers — the permission to be a little lighter, a little more present, a little less defended — does not have to turn with it. Thich Nhat Hanh understood something that neuroscience has spent decades proving: the smile and the joy are in conversation with each other, and either one can start the exchange. You do not have to wait to feel happy before your face reflects it, because the face is not simply a mirror of the interior — it is also one of its most powerful levers.

It requires no prescription, no appointment, no device. It is available in the middle of a stressful commute, in the pause between one meeting and the next, in the mirror before the day begins. The research is clear, the mechanism is understood, and the only question is whether — as September settles in and the pace of life reasserts itself — we give ourselves permission to use it.

Credits and Sources

1. Thich Nhat Hanh, The Miracle of Mindfulness, 1975

2. Coles NA, et al. "A multi-lab test of the facial feedback hypothesis by the Many Smiles Collaboration." Nature Human Behavior, 2022 — 3,878 participants across 19 countries

3. Kraft TL, Pressman SD. "Grin and Bear It: The Influence of Manipulated Facial Expression on the Stress Response." Psychological Science, University of Kansas, 2012

4. Abel EL, Kruger ML. "Smile Intensity in Photographs Predicts Longevity." Psychological Science, 2010. Note: a 2022 replication by Strick and colleagues using a larger sample did not reproduce the longevity finding — the relationship between smile intensity and lifespan remains debated in the literature

5. Niedenthal PM, et al. "Social functionality of smiles." Emotion Review, 2017

6. National Geographic, "A smile isn't just contagious — it may change who you trust," July 2026

7. Walden University, "The Power of Smiling" — waldenu.edu

8. LCMC Health / West Jefferson Medical Center, "Turn That Frown Upside Down to Realize the Benefits of Smiling," May 2024

9. National Institute on Aging — Women's Health Initiative optimism and longevity study, 150,000 participants

10. 2025 study on entrepreneurial smiling and venture capital outcomes — PubMed

11. Coles NA et al. "Effects of posed smiling on memory for happy and sad facial expressions." PMC, 2021

12. University College London study on smiling and exercise endurance, 2014 — cited in Gitnux smiling statistics

13. Hayre N. "Clinical Study Points to Oxytocin's Antiaging Benefits." Dermatology Times, June 2026