Stress is an unavoidable part of life, and while it often carries a negative connotation, it is actually a fundamental survival mechanism. When faced with a perceived threat, whether physical or emotional, the body instinctively reacts to protect itself. This automatic response is commonly known as the "fight, flight, or freeze" response. While it serves an essential function in dangerous situations, chronic activation of this response due to daily stressors can have significant consequences for mental and physical health.

The body’s response to stress is rooted in human evolution. When our ancestors encountered a predator, their nervous systems immediately prepared them to either confront the threat (fight), escape to safety (flight), or become still and unnoticed (freeze). While modern-day stressors may not include wild animals, our nervous system reacts similarly to job pressures, financial worries, or social conflicts.

According to the Cleveland Clinic, stress is the body's response to change, activating a physiological reaction that helps us adapt and protect ourselves. While short-term stress can be beneficial, prolonged exposure can lead to an overactive stress response, negatively impacting overall well-being.

The Three Stress Responses: Fight, Flight, and Freeze

1. Fight

The fight response prepares the body for direct action. When triggered, the nervous system releases adrenaline, increasing heart rate, blood pressure, and muscle tension. While this reaction once helped early humans fend off predators, today it manifests as irritability, frustration, or aggression.

For instance, the employee who has experienced too much workload may work extremely long hours just to succeed. In short term, the action may produce good results but mostly ends in burnout, anxiety, and physical illness, for example, tension headache or digestion problems.

2. Fight

The flight response triggers an intense need to remove oneself from a stressful situation. Just as our ancestors would flee from danger, modern individuals may avoid conflict, quit jobs impulsively, or detach from relationships when overwhelmed.

Flight mode is linked with restlessness and anxiety. Individuals may have a sense of needing to get up and go-pacing, changing environments constantly, or avoiding tasks that seem too overwhelming. Someone with a flight response might have the desire to change jobs constantly, relocate constantly, or become reclusive in order to avoid perceived dangers.

3. Freeze

The freeze response occurs when the nervous system perceives a threat as too overwhelming to fight or flee. Rather than taking action, individuals shut down, feeling numb, disconnected, or paralyzed by fear.

Unlike fight or flight, which involve heightened activation, freeze mode slows down physiological functions. A person experiencing freeze mode may feel physically unable to move, struggle to make decisions, or find themselves dissociating from their emotions. This can manifest in situations such as public speaking anxiety, where someone might "blank out" or feel stuck in the moment.

What Happens in the Body During A Stressful Event?

When faced with a stressor, the autonomic nervous system (ANS) activates, triggering physiological changes, including:

• Increased heart rate and breathing: The body pumps more oxygen to muscles and the brain in case action is needed.
• Muscle tension: The body prepares for movement, sometimes causing trembling or stiffness.
• Dilated pupils: Vision sharpens to detect potential threats.
• Dry mouth: Saliva production decreases as the body redirects energy to essential functions.
• Changes in skin tone: Blood flow is directed to vital organs, sometimes making the skin appear pale or flushed.

For those experiencing the freeze response, the body undergoes a different reaction, often reducing heart rate and causing physical immobility rather than heightened activation.

Strategies for Coping and Managing the Stress Response

While the stress response is necessary for survival, frequent activation due to daily stressors can take a toll on health. Recognizing your default response—whether fight, flight, or freeze—can help in developing effective coping mechanisms.

1. Moving to a Safe Space

If possible, changing your environment can help signal to your brain that the threat has passed. Stepping outside for fresh air, finding a quiet place, or distancing yourself from overwhelming stimuli can help regulate emotions.

2. Practicing Controlled Breathing

Deep, slow breathing can be used to counteract the stress response by engaging the parasympathetic nervous system, which promotes relaxation. Techniques such as diaphragmatic breathing or the 4-7-8 method (inhale for four seconds, hold for seven, exhale for eight) can be particularly effective in calming the body.

3. Engaging in Physical Activity

This helps release pent-up energy and aids in the endorphin cascade, natural boosters for our mood.

4. Seeking Social Support

Relieving oneself from stress can come in many ways, but sharing it with trusted friends, a family member, or a good therapist will sure give that psychological boost of hope. Social support is an especially effective way of cushioning people against the stressors that they are subjected to in chronic forms.

When to Seek Professional Help

While occasional stress is normal, chronic activation of the fight, flight, or freeze response can indicate underlying mental health concerns, such as anxiety disorders or post-traumatic stress disorder (PTSD). If stress is affecting daily life—leading to sleep disturbances, difficulty concentrating, or persistent feelings of fear—it may be time to consult a mental health professional.

After Dussehra festivities, Delhi woke up to an alarming AQI of 300, maybe even more in some parts of the city. On October 21, pollution curbs under GRAP-1 were implemented, which are brought in force when AQI ranges between 201 and 300.

As Delhi's air pollution increases, some people may experience uncommon symptoms like feeling unusually tired, sluggish or unable to concentrate. This is not just a coincidence. Even people without asthma or breathing difficulties can feel fatigue, especially during periods of high air pollution.

Fine particulate matter (PM2.5) can penetrate deep into the lungs and trigger inflammation and physiological stress. Its effects may extend beyond the respiratory system, affecting blood vessels health, cardiovascular function as well as sleep.

HeathandMe spoke to Dr Puneet Khanna, Chairman, Respiratory Medicine and Pulmonology, Manipal Hospital Dwarka, New Delhi, Dr. Puneet Gupta, HOD - Pulmonology, Intervention Pulmonology & Sleep Medicine, Yatharth Super Speciality Hospital, Noida Extension, and Dr Mrinal Sircar, Director, Respiratory and Sleep Medicine, Medanta, Noida, who explained why rising AQI can leave some people feeling exhausted, what can help and when chronic fatigue needs medical attention.

High AQI May Make You Feel Tired Even Without Breathing Problems

Poor air quality does not affect just the lungs. Dr Sircar explains that air pollution can cause symptoms even in people without a pre-existing respiratory condition.

According to Dr Khanna, exposure to PM2.5 can trigger inflammation and oxidative stress, increase the body's workload and affect sleep quality. These changes may contribute to tiredness, headaches, low energy and reduced concentration, even in people with otherwise healthy lungs.

“Exposure to polluted air may also affect sleep quality and increase the body's overall stress response, contributing to symptoms such as tiredness, reduced energy and difficulty concentrating,” he says.

Dr. Gupta delves deeper into the process of PM2.5's attack and how the body responds to it.

He explained, "Your immune system treats fine particles (PM2.5) as intruders and mounts a constant low-grade defence, which burns energy much like a mild infection. At the same time, irritated airways and gases like carbon monoxide can make oxygen delivery slightly less efficient. The most underrated cause is sleep: a dry throat, blocked nose, and mild night-time cough fragment your sleep, so you wake up unrefreshed without knowing why. Fatigue here doesn’t mean your lungs are weak. It means your body is working overtime quietly."

Also read: Sky Turns Orange In Indonesia: How Toxic Smog From Wildfires Can Impact Health

Can PM2.5 Affect The Heart And Blood Vessels Too?

PM2.5 particles are small enough to penetrate deep into the lungs. Some of its components can even enter the bloodstream. Exposure can trigger inflammatory and oxidative stress responses beyond the respiratory system.

Dr Khanna says, “These changes may reduce physical endurance, increase feelings of fatigue, and contribute to symptoms such as brain fog, lethargy, and reduced exercise tolerance, particularly during periods of severe air pollution.”

Dr. Gupta explained PM2.5 can create the same response from body as a common flu does. But the extent of these effects depends on pollution levels, duration of exposure and individual risk.

He said, "PM2.5 is small enough that it, or the inflammatory chemicals it triggers, can enter the bloodstream. Signalling molecules such as IL-6 and CRP then travel through the whole body and produce the same “wiped out” feeling you get with the flu."

He also said that particles also create oxidative stress, which damages mitochondria, the power plants of your cells. Blood vessels become stiffer, blood pressure can rise slightly, and the nervous system’s control of heart rhythm can be disturbed, which may feel like heaviness or palpitations. Inflammation can also reach the brain, causing fog and poor focus.

Also read: Delhi Smog: Can You Really Tackle Pollution Season With An N95 Mask And Air Purifier?

What Can Help?

According to the doctors, the key is to reduce exposure to polluted air. Practical steps include:

• Limit exertion: Avoid strenuous outdoor activity when pollution levels are high, especially during periods of severe pollution.
• Wear a well-fitting N95 respirator: It can reduce exposure to fine particles when outdoors.
• Improve indoor air quality: Keep windows closed when outdoor air quality is poor and use a suitably sized air purifier with a HEPA filter where feasible.
• Maintain basic health routines: Get adequate sleep, stay hydrated and eat regular meals.
• Check AQI levels: Use local air quality updates to plan outdoor activities.

Dr Khanna emphasises that these steps can help reduce exposure but cannot eliminate the effects of ongoing pollution. He also said that severe breathlessness, chest pain, fainting or sudden weakness requires urgent medical attention.

Does Pollution-Induced Fatigue Go Away When AQI Improves?

For many otherwise healthy people, symptoms can improve once air quality improves. Dr Khanna says recovery may occur within a few hours to several days, depending on pollution severity, exposure duration and individual health.

However, there is no fixed recovery timeline. People with underlying respiratory or cardiovascular conditions may take longer to recover, while persistent tiredness may point to another health problem.

Dr Sircar advises seeking medical advice if fatigue continues after air quality improves.

The doctors also advise that if fatigue is chronic, recurrent, worsening or interferes with daily activities, medical evaluation should be sought rather than simply attributing it to air pollution.

Dr Sircar also says that that a doctor may need to investigate other possible causes, including anaemia, thyroid disorders, sleep problems and cardiovascular conditions. Fatigue accompanied by a chronic cough, wheezing, breathlessness, chest problems or reduced exercise tolerance also needs intervention.

A single photograph of someone’s face might carry real clues about their health and how long they’re likely to live, at least according to new AI tools built by researchers at Mass General Brigham in Boston.

What the researchers built

The team trained a large AI foundation model called FAHR-Face, short for Foundation Artificial Intelligence for Health Recognition, on more than 40 million facial images.

From that base model, they built two specialised tools: FAHR-FaceAge, which estimates a person’s biological age from a single photo, and FAHR-FaceSurvival, fine-tuned on 34,389 photos of cancer patients to predict survival risk directly from facial appearance.

“I was pretty surprised to find out that we could pick up signs of mortality risk from just a facial photograph,” corresponding author is Dr. Raymond Mak, a radiation oncologist at Mass General Brigham Cancer Institute told CNN. The study is published in The Lancet Digital Health.

What the two tools actually look at

The two algorithms focus on entirely different parts of the face. “The age estimation algorithm is looking at the area around the temples, the area on the forehead, above the eyes and then what we call the nasolabial fold,” Mak said, while “the mortality risk prediction algorithm is looking at a totally different part of the face... the bridge of the nose and the area under the eyes.”

Also Read: ADHD Linked To 71% Higher Risk Of Death; Suicide And Injuries Among Top Concerns

The results

Among 122 cancer patients flagged by FAHR-FaceSurvival as high-risk, 52.5% died within 90 days, compared with about 2% of the 975 patients in the lowest-risk group. Separately, 21% of patients whose biological age came back more than 20 years older than their actual age died within 90 days, against about 6% of those whose biological age was at least 10 years younger than their chronological age.

The researchers also found that cosmetic changes, including surgery, Botox, or makeup, didn’t throw off the models’ performance, according to the Mass General Brigham release.

An eerie echo of ancient medicine

The facial regions both AI models rely on, the nose, temples, and the area around the eyes, closely match what the Greek physician Hippocrates described around 400 BC in his Book of Prognostics as signs of approaching death: “the nose sharp, the eyes sunken, the temples fallen in.”

Mak told CNN the algorithms had no exposure to Hippocrates’ text and were trained purely on photographs and outcomes data. “Hearing Hippocrates echo over millennia in our algorithms was very eerie,” he said.

Not ready for the clinic yet

Outside experts urged caution. Dr. Wilbur Lam of Emory University, who wasn’t involved in the study, called it “an extremely compelling study” with robust associations, but said its “true clinical utility... will need to be demonstrated prospectively,” and flagged open questions about how well it performs across different facial features, skin tones, and age groups.

Miroslaw Bober of the University of Surrey, also not involved in the study, said the findings shows “convincing evidence” of a statistical link but cautioned that “predicting an outcome is not the same as explaining it.”

He noted the study never tested whether the AI model picks up anything a doctor’s own assessment wouldn’t, since doctors’ general health evaluations weren’t measured for comparison. “This is a promising proof of concept, but it is not ready for clinical use,” Bober said.

An individual's income, education, gender and place of residence can impact their risk of developing chronic diseases, as well as their access to diagnosis and treatment, according to a new World Health Organization (WHO) report.

The report highlights how social and economic inequalities affect the burden of noncommunicable diseases (NCDs) like cancer, cardiovascular diseases, diabetes and chronic respiratory diseases.

Published on October 20, State of Inequality: Noncommunicable Diseases and Their Risk Factors is WHO's first comprehensive global assessment of inequalities in NCDs and their risk factors. The report is based on data sources from nine countries and examines 35 indicators, using national data that collected over the past decade.

NCDs account for about three-quarters of deaths worldwide but their impact is not shared equally across different countries and their populations. The report examines how differences in economic status, education, sex, age, disability, employment, migration status and location influence disease risks and access to healthcare.

“This is the first effort to systematically measure inequalities in NCDs and their risk factors on a global scale,” said Dr Ahmad Reza Hosseinpoor, who leads WHO's health inequality monitoring team. “The findings show which populations are being left behind.”

How Income And Education Influence Chronic Disease Risk

The report found that people with lower levels of education in low and middle income countries tend to have higher rates of hypertension and diabetes.

Education can affect access to credible health information, opportunities to make informed health decisions and the capability to navigate technically complex healthcare services.

Income becomes a key factor that affects whether people's ability to afford nutritious food, preventive care, medicines and routine medical check-ups.

The report found that the poorest and least-educated women were less likely to receive cervical cancer screening. Tobacco use was also higher among men who were less educated than their educated counterparts.

Also read: G155E H1N1 Mutation In US Raises Concerns: Can This Year’s Flu Shot Still Protect You?

Risk Is Also Affected By Gender And Location

Differences in healthcare access and risks were also observed between men and women. Men were more likely to use tobacco and consume alcohol, but men with hypertension were less likely to be diagnosed and treated than women.

Women were less likely to meet recommended physical activity levels, while obesity was more common among women, particularly in low and middle-income countries.

Geography was another key factor as in many underprivileged countries, people living in rural areas had less access to hypertension diagnosis and treatment, as well as cervical cancer screening.

Rural households could also face greater exposure to household air pollution, while urban populations often experienced greater exposure to outdoor air pollution.

People with disabilities and migrants may also face financial, administrative, geographical or language barriers that make prevention, screening and treatment harder to access.

Also read: Lead Poisoning: WHO Warns There Is No Known Safe Level; Flags Risks From Paint, Spices and Cookware

What Needs To Change According To WHO

WHO said countries should use inequality data to identify marginalised populations who face barriers to enable direct prevention and treatment services towards them.

The report recommends expanding interventions to reduce NCD risks, improving access to screening and treatment in weak communities, and collecting data that reveal differences between population groups.

“Inequality data are not simply about documenting differences – they are a tool for action,” said Dr Alain Labrique, director of WHO's Data, Digital Health, Analytics and AI Department. “They help countries better tailor policies and programmes, identify gaps in coverage and track whether progress is reaching all population groups.”