Our ancient fight-or-flight response may contribute to modern ailments

Stress evolved as a survival mechanism to keep humans alive

Stress activates the “fight-or-flight” response when we face threats. It’s triggered by the hypothalamus, which signals the release of adrenaline and cortisol, heightening awareness and energy. While acute stress helps in short bursts, chronic stress—persistent over time—can harm both physical and mental health, leading to conditions like hypertension, anxiety, or depression.

Chronic stress affects nearly all parts of the body

Stress is our body’s internal mechanism to deal with changes in our internal balance. As such, the stress response affects nearly every organ system through a cascade of both fast and slow hormonal changes. While short-term stress can be adaptive, long-term stress may cause serious health issues.

The biology of stress in your body

Stress is a normal human response that has evolved over millions of years to handle changes or threats in our environment. This article is a helpful overview of the biological basics of this response. While it is not harmful to our physiology in the acute setting, chronic stress can lead to damaging changes in the human body over many years.

Stress-induced adrenaline can trigger a 'hysterical strength' response

The stress response is a powerful ancient mechanism designed to maximize human survival—it can even result in superhuman strength. The adrenal glands are located just above the kidneys, and stress-induced adrenaline release causes more blood (and therefore more oxygen) to flow to your muscles, increasing performance.

Fear (and stress) can be contagious via pheromones secreted by the body

While seeing someone else in a panicked state may induce a stress response, researchers have found stress can be literally contagious—chemicals contained in sweat and other secretions can trigger stress hormone release in others. Theories suggest this feature is an evolutionary adaptation to protect groups from danger.

Autoimmune disease prevalence and incidence are on the rise—but no one knows why

Researchers theorize that environmental factors, including shifts to less healthy diets, air pollution, infections, stress, climate change, and exposures to xenobiotics—substances like pesticides, plastics, and toxins that incite immune responses—may all be fueling epigenetic changes to our bodies that make people's immune responses go awry.

How we frame stress—as good or bad—seems to alter how it affects us

This podcast discusses research that indicates stress perception may drastically affect how we respond to it. In research exploring if our stress is presented as diminishing our health versus if we're told it enhances our performance, it will lead to differences in how successful participants are at performing tasks—with the enhancers doing better.

Short-term cortisol spikes can boost the immune system

Elevated acute levels can enhance the immune system's ability to fight off infection or respond to injury. Chronic heightened cortisol levels, however, can lead to inflammation that harms cells and tissues over time.

Brain conditions and surgery can cause some individuals to feel no fear

Fear is a survival mechanism that originates in the brain's amygdala, triggering the body's fight-or-flight response. However, in modern society, without the same natural dangers, fear can lead to anxiety and mental health issues when unnecessarily triggered. Understanding individuals without fear may help identify new methods to treat anxiety disorders.

Why some people have allergies

Why do some people have allergies while others don’t? One theory suggests allergies are a relic of our evolutionary past. Our immune system, once primed to fight parasites, now mistakes harmless substances for threats.

Modern workplaces were engineered for efficiency, not work-life balance

Modern work organization traces back to 19th-century scientific management, an approach that optimized output by viewing workers as machine components. That logic still persists today and contributes to burnout, stress, and disengagement. Researchers propose a "circular work" model that combines effort with recovery, learning, and renewal, suggesting productivity and well-being should align rather than compete.

Inflammaging appears to differ across global populations

Chronic, low-grade inflammation linked to aging is a byproduct of our industrialized lifestyles, according to recent research. The work compared two industrialized populations with two Indigenous, non-industrialized populations in Bolivia and Malaysia, and found that inflammation levels in the Indigenous groups—unlike the industrialized ones—did not seem to differ by age.

Optimal human functioning requires movement

There is now ample evidence to back the centuries-old hypothesis that exercise is critical to human health. This review article explores the latest discoveries in exercise science, including how exercise is intrinsic to maintaining our organ systems throughout life.

How trauma gets ‘under the skin’

A study examining the muscle function of older adults who have at least one adverse childhood experience (ACE) suggests that trauma digs itself into muscle cells. Participants who reported childhood trauma were found to have lower maximum levels of cellular energy than people who reported fewer or no ACEs. Such compromised mitochondrial function "doesn't bode well," as it relates to a variety of health and age-related outcomes.

Diabetes is a hormonal disorder

Hormones are naturally produced in the body in concert with cell receptors, influencing how cells behave, but diseases that affect hormonal production, including those produced by the pancreas or the thyroid, can upend those processes.

Food allergies were first documented more than 4,000 years ago

Although food allergies are on the rise in modern times, they have been documented in written records for thousands of years. More than 3,000 years ago, Chinese emperors advised patients to avoid certain foods, and Hippocrates noted in his work that food could cause serious harm to certain individuals, and even lead to death.

The science of spring fever

Researchers have confirmed what people have sensed for ages: Our emotions during the springtime can go a little wild. This piece breaks down the impact of the seasonal transition on our bodies and prescribes a few ways to mitigate the effects.

How artificial intelligence, which detects patterns, can identify burnout

Researchers are training AI to detect stress-related symptoms, helping physicians and other medical workers recognize and reduce stress from overwork and potentially avoid burnout.

Can humans delay or reverse old age?

We're not sure yet. Researchers at the University of California San Francisco are studying why some conditions and behaviors, such as low-oxygen environments and exercise, benefit the aging process, hoping to reveal potential health applications. Some of this research focuses on klotho, a naturally occurring age-regulating hormone named after the Greek Fate Clotho. Animal studies on klotho brain injections found subjects had improved memory recall and age-related degeneration resistance.

The dark side of modern sugar production

Humanity's ancestors evolved to wring more calories from sugary fruits by storing excess sugar as fat, an adaption that's culminated in many peoples' palettes preferring calorie-rich sweet. Now, the desire for sugar has both contributed to a widespread health crisis and been at the center of atrocities around the world.

Noise pollution from humans and technology alters animal behavior

Animals may experience chronic stress and health issues due to noise pollution, which often interferes with their mating sounds. Due to traffic, nightingales sing louder on weekday mornings, and birds near airports start singing earlier to avoid upticks in takeoffs and landings.

Dinosaurs suffered from cancer, arthritis, and infections seen in modern animals

Using CT scans and advanced pathology techniques, paleopathologists have identified respiratory illnesses, malignant osteosarcoma, and other diseases in dinosaurs. The research has helped show how many of these ailments are not exclusively modern phenomena.

How the gut microbiome can affect heatstroke risk

Some research suggests that our gut microbiome influences our risk of exertional heatstroke. If exercise boosts our body temperatures to unsafe levels, increasing gut permeability, that can cause a "leaky" gut—allowing bacteria and other gut microbes to leak into the bloodstream and potentially trigger endotoxemia, a potentially life-threatening inflammatory response that can occur with heat exhaustion and heatstroke.

Schizophrenia symptoms, like psychosis, often first emerge among young adults

A combination of genetics, significant brain changes to the frontal cortex, and hormonal changes during young adulthood—late teens to early 30s—result in schizophrenic symptoms often showing up during this period. The stress of life changes at that age may also be a contributing factor.

Why human brains were bigger 3,000 years ago

Our modern civilisation may be the most advanced to ever exist on Earth, but around 100 generations ago, our ancestors had brains that were larger than our own.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

In recent years a child anxiety expert has created and tested a novel phobia and anxiety treatment approach for children, focused on changing how parents respond to the fears.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

Some researchers have labeled nomophobia, the fear of being without your phone, as 'the phobia of the 21st century.'

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

Scientists testing how climate change affects plants found, in a years-long simulation study, that poison ivy grew 70% faster with the resulting extra carbon dioxide.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

See these 16 pieces of art evoking phobias of snakes, flying, spiders, and more. 

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Watch what the Ebola virus does inside our cells and organs in order to spread and survive.

Astronauts have repaired genetic damage in space using CRISPR—a molecular tool that can make precise changes to DNA and is used in single-celled organisms to attack invasive viruses.

20,000 letters to the advice columnist 'Dear Abby' provide insight into prevailing sex, religion, and LGBTQ fears, anxieties, and concerns from the 1950s onward.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

The power and influence of the American presidency have expanded significantly over time—far beyond what the founders envisioned.

US consumers collectively owe more than $1T to credit card companies—almost as much as they owe in auto loans.

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

Existentialist writer Jean-Paul Sartre coined the famous phrase 'Hell is—other people' in his play 'No Exit'