Understanding the stress response - Harvard Health (2023)

Chronic activation of this survival mechanism impairs health

Understanding the stress response - Harvard Health (1)

A stressful situation — whether something environmental, such as a looming work deadline, or psychological, such as persistent worry about losing a job — can trigger a cascade of stress hormones that produce well-orchestrated physiological changes. A stressful incident can make the heart pound and breathing quicken. Muscles tense and beads of sweat appear.

This combination of reactions to stress is also known as the "fight-or-flight" response because it evolved as a survival mechanism, enabling people and other mammals to react quickly to life-threatening situations. The carefully orchestrated yet near-instantaneous sequence of hormonal changes and physiological responses helps someone to fight the threat off or flee to safety. Unfortunately, the body can also overreact to stressors that are not life-threatening, such as traffic jams, work pressure, and family difficulties.

Over the years, researchers have learned not only how and why these reactions occur, but have also gained insight into the long-term effects chronic stress has on physical and psychological health. Over time, repeated activation of the stress response takes a toll on the body. Research suggests that chronic stress contributes to high blood pressure, promotes the formation of artery-clogging deposits, and causes brain changes that may contribute to anxiety, depression, and addiction.. More preliminary research suggests that chronic stress may also contribute to obesity, both through direct mechanisms (causing people to eat more) or indirectly (decreasing sleep and exercise).

(Video) Understanding the Stress Response System

Sounding the alarm

The stress response begins in the brain (see illustration). When someone confronts an oncoming car or other danger, the eyes or ears (or both) send the information to the amygdala, an area of the brain that contributes to emotional processing. The amygdala interprets the images and sounds. When it perceives danger, it instantly sends a distress signal to the hypothalamus.

Command center

Understanding the stress response - Harvard Health (2)

When someone experiences a stressful event, the amygdala, an area of the brain that contributes to emotional processing, sends a distress signal to the hypothalamus. This area of the brain functions like a command center, communicating with the rest of the body through the nervous system so that the person has the energy to fight or flee.

(Video) Responding to stress | Processing the Environment | MCAT | Khan Academy

The hypothalamus is a bit like a command center. This area of the brain communicates with the rest of the body through the autonomic nervous system, which controls such involuntary body functions as breathing, blood pressure, heartbeat, and the dilation or constriction of key blood vessels and small airways in the lungs called bronchioles. The autonomic nervous system has two components, the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system functions like a gas pedal in a car. It triggers the fight-or-flight response, providing the body with a burst of energy so that it can respond to perceived dangers. The parasympathetic nervous system acts like a brake. It promotes the "rest and digest" response that calms the body down after the danger has passed.

After the amygdala sends a distress signal, the hypothalamus activates the sympathetic nervous system by sending signals through the autonomic nerves to the adrenal glands. These glands respond by pumping the hormone epinephrine (also known as adrenaline) into the bloodstream. As epinephrine circulates through the body, it brings on a number of physiological changes. The heart beats faster than normal, pushing blood to the muscles, heart, and other vital organs. Pulse rate and blood pressure go up. The person undergoing these changes also starts to breathe more rapidly. Small airways in the lungs open wide. This way, the lungs can take in as much oxygen as possible with each breath. Extra oxygen is sent to the brain, increasing alertness. Sight, hearing, and other senses become sharper. Meanwhile, epinephrine triggers the release of blood sugar (glucose) and fats from temporary storage sites in the body. These nutrients flood into the bloodstream, supplying energy to all parts of the body.

All of these changes happen so quickly that people aren't aware of them. In fact, the wiring is so efficient that the amygdala and hypothalamus start this cascade even before the brain's visual centers have had a chance to fully process what is happening. That's why people are able to jump out of the path of an oncoming car even before they think about what they are doing.

As the initial surge of epinephrine subsides, the hypothalamus activates the second component of the stress response system — known as the HPA axis. This network consists of the hypothalamus, the pituitary gland, and the adrenal glands.

(Video) A to Z of the Fight or Flight Response

The HPA axis relies on a series of hormonal signals to keep the sympathetic nervous system — the "gas pedal" — pressed down. If the brain continues to perceive something as dangerous, the hypothalamus releases corticotropin-releasing hormone (CRH), which travels to the pituitary gland, triggering the release of adrenocorticotropic hormone (ACTH). This hormone travels to the adrenal glands, prompting them to release cortisol. The body thus stays revved up and on high alert. When the threat passes, cortisol levels fall. The parasympathetic nervous system — the "brake" — then dampens the stress response.

Techniques to counter chronic stress

Many people are unable to find a way to put the brakes on stress. Chronic low-level stress keeps the HPA axis activated, much like a motor that is idling too high for too long. After a while, this has an effect on the body that contributes to the health problems associated with chronic stress.

Persistent epinephrine surges can damage blood vessels and arteries, increasing blood pressure and raising risk of heart attacks or strokes. Elevated cortisol levels create physiological changes that help to replenish the body's energy stores that are depleted during the stress response. But they inadvertently contribute to the buildup of fat tissue and to weight gain. For example, cortisol increases appetite, so that people will want to eat more to obtain extra energy. It also increases storage of unused nutrients as fat.

Fortunately, people can learn techniques to counter the stress response.

(Video) 2-Minute Neuroscience: HPA Axis

Relaxation response. Dr. Herbert Benson, director emeritus of the Benson-Henry Institute for Mind Body Medicine at Massachusetts General Hospital, has devoted much of his career to learning how people can counter the stress response by using a combination of approaches that elicit the relaxation response. These include deep abdominal breathing, focus on a soothing word (such as peace or calm), visualization of tranquil scenes, repetitive prayer, yoga, and tai chi.

Most of the research using objective measures to evaluate how effective the relaxation response is at countering chronic stress have been conducted in people with hypertension and other forms of heart disease. Those results suggest the technique may be worth trying — although for most people it is not a cure-all. For example, researchers at Massachusetts General Hospital conducted a double-blind, randomized controlled trial of 122 patients with hypertension, ages 55 and older, in which half were assigned to relaxation response training and the other half to a control group that received information about blood pressure control. After eight weeks, 34 of the people who practiced the relaxation response — a little more than half — had achieved a systolic blood pressure reduction of more than 5 mm Hg, and were therefore eligible for the next phase of the study, in which they could reduce levels of blood pressure medication they were taking. During that second phase, 50% were able to eliminate at least one blood pressure medication — significantly more than in the control group, where only 19% eliminated their medication.

Physical activity. People can use exercise to stifle the buildup of stress in several ways. Exercise, such as taking a brisk walk shortly after feeling stressed, not only deepens breathing but also helps relieve muscle tension. Movement therapies such as yoga, tai chi,and qi gong combine fluid movements with deep breathing and mental focus, all of which can induce calm.

Social support. Confidants, friends, acquaintances, co-workers, relatives, spouses, and companions all provide a life-enhancing social net — and may increase longevity. It's not clear why, but the buffering theory holds that people who enjoy close relationships with family and friends receive emotional support that indirectly helps to sustain them at times of chronic stress and crisis.

(Video) Turning Fear into Power: Understanding and managing anxiety - Longwood Seminar


What did the Harvard study reveal about stress? ›

Research suggests that chronic stress contributes to high blood pressure, promotes the formation of artery-clogging deposits, and causes brain changes that may contribute to anxiety, depression, and addiction..

How do you respond to stress marathon health? ›

Deep breathing, meditation, mindfulness, yoga, exercise, and even venting to a trusted friend can all help reduce the negative impacts stress can have on your body. “The two most beneficial ways counseling can help manage stress is by providing an outlet and education,” Alisa says.

What are the three stages of the stress response your answer? ›

[18] This syndrome is divided into the alarm reaction stage, resistance stage, and exhaustion stage. The alarm reaction stage refers to the initial symptoms of the body under acute stress and the "fight or flight" response.

What is the stress response quizlet? ›

What is the stress response? A set of complex physiological interactions, sometimes called the neuro-endocrine response or psych-neuro-immunologic response.

What were the findings of the Harvard study? ›

The most consistent finding we've learned through 85 years of study is: Positive relationships keep us happier, healthier, and help us live longer. Period.

What were the findings of the Harvard report? ›

“Over nearly 150 years, from the university's founding in 1636 until the Massachusetts Supreme Judicial Court found slavery unlawful in 1783, Harvard presidents and other leaders, as well as its faculty and staff, enslaved more than 70 individuals, some of whom labored on campus,” the report said.

What is the stress response theory? ›

The stress response includes physical and thought responses to your perception of various situations. When the stress response is turned on, your body may release substances like adrenaline and cortisol. Your organs are programmed to respond in certain ways to situations that are viewed as challenging or threatening.

What are the 5 levels of stress? ›

There are five stages of stress; fight or flight, damage control, recovery, adaption, and burnout.

What are 3 positive ways respond to stress? ›

Here are some healthy ways you can deal with stress:
  • Take breaks from watching, reading, or listening to news stories, including those on social media. ...
  • Take care of yourself. ...
  • Take care of your body. ...
  • Make time to unwind. ...
  • Talk to others. ...
  • Connect with your community- or faith-based organizations.
  • Avoid drugs and alcohol.

How do you complete the stress response cycle? ›

Here's a simple one: breathe in slowly for five seconds, hold that breath for five more seconds, and exhale for ten seconds. Just a few minutes of this practice can calm down your vagus nerve and complete your fight-or-flight stress response.

What are the 4 warning signs of stress? ›

If you are stressed, you might feel:
  • Irritable, angry, impatient or wound up.
  • Over-burdened or overwhelmed.
  • Anxious, nervous or afraid.
  • Like your thoughts are racing and you can't switch off.
  • Unable to enjoy yourself.
  • Depressed.
  • Uninterested in life.
  • Like you've lost your sense of humour.

What is a stress response example? ›

Increased heart rate and respirations. Increased blood pressure. Upset stomach, nausea, diarrhea. Increased or decreased appetite which may be accompanied by weight loss or gain.

Which of the following happens during a stress response? ›

When stress happens, it makes more of the hormone ACTH. This hormone tells your adrenal glands to make more of their stress hormones. These stress hormones help you to focus, speed up your reaction time, and boost your strength. Your hypothalamus also helps your body respond to stress.

What are the three stages of the stress response quizlet? ›

The stress response occurs in three stages:
  • an initial fight‐or‐flight response.
  • a slower resistance reaction.
  • exhaustion.

What is the Harvard case about? ›

The plaintiff, Students for Fair Admissions, alleged that Harvard used the personal ratings to depress Asian American admissions and effect an unspoken quota. Judge Burroughs rejected this argument.

What are 3 great things about Harvard? ›

Harvard students have access to courses, research institutes, and faculty mentors from all parts of Harvard. With world-renowned faculty, state-of-the-art resources, and individualized instruction, it's the perfect place to pursue your favorite and still-to-be-discovered academic interests.

What was the main purpose of the Harvard Grant study? ›

Grant. It began with 268 men who were sophomores at Harvard between 1939 and 1944. Bock wanted to get away from medicine's tendency to focus on the small, specialized and sickly. He wanted to study successful and normal men, to see what makes a good life and maybe even decipher a general recipe for success.

What did a Harvard study reveal about goals and success? ›

There was a study done at Harvard between 1979 and 1989. Graduates of the MBA program were asked “Have you set clear written goals for your future and made plans to accomplish them?” The results of that question were: Only 3% had written goals and plans. 13% had goals but not in writing.

What were the main lessons learned from the longest study on happiness? ›

It's the longest in-depth longitudinal study on human life ever done, and it's brought us to a simple and profound conclusion: Good relationships lead to health and happiness. The trick is that those relationships must be nurtured.

How does Harvard evaluate students? ›

The College treats each applicant as an individual, and holds an expansive view of excellence; the admissions committee looks at the whole person and considers each applicant's unique background and experiences, alongside grades and test scores, to find applicants of exceptional ability and character, who can help ...

What are the 4 stages of the stress response describe? ›

The alarm phase described by Selye consists of four phases: threat, organization, fight and flight, and recovery/shock. These are related to the four grades of fear: anxiety, fear, panic, and horror.

Who defined stress as the response? ›

The word 'stress' is used in physics to refer to the interaction between a force and the resistance to counter that force, and it was Hans Selye who first incorporated this term into the medical lexicon to describe the “nonspecific response of the body to any demand “.

How does stress affect your health? ›

This can put you at increased risk for a variety of physical and mental health problems, including anxiety, depression, digestive issues, headaches, muscle tension and pain, heart disease, heart attack, high blood pressure, stroke, sleep problems, weight gain, and memory and concentration impairment.

What are the 3 A's of stress? ›

When deciding which option to choose, it's helpful to think of the four A's: avoid, alter, adapt or accept. Since everyone has a unique response to stress, there is no “one size fits all” solution to managing it.

What is the 5 5 5 rule for stress? ›

First, you may want to start with a simple deep breathing exercise called the 5-5-5 method. To do this, you breathe in for 5 seconds, hold your breath for 5 seconds, and then breathe out for 5 seconds. You can continue this process until your thoughts slow down or you notice some relief.

What are 4 main categories causes of stress? ›

Stress factors broadly fall into four types or categories: physical stress, psychological stress, psychosocial stress, and psycho-spiritual stress.

How do you turn stress into strength? ›

Our lives have become increasingly stressful. How can we turn this stress into resilience?
  1. Expect the unexpected and learn to be flexible.
  2. Control what you can and put down the rest.
  3. Meet challenges with excitement.
  4. Harness your stress response for resilience, better health, and longevity.
Jan 10, 2023

What are the 2 types of positive stress? ›

Examples of positive personal stressors include:
  • Receiving a promotion or raise at work.
  • Starting a new job.
  • Marriage.
  • Buying a home.
  • Having a child.
  • Moving.
  • Taking a vacation.
  • Holiday seasons.

What causes stress? ›

It can come from any event or thought that makes you feel frustrated, angry, or nervous. Stress is your body's reaction to a challenge or demand. In short bursts, stress can be positive, such as when it helps you avoid danger or meet a deadline. But when stress lasts for a long time, it may harm your health.

What are the 6 Fs of stress response? ›

In the most extreme situations, you might have lapses of memory or “lost time.” Schauer & Elbert (2010) refer to the stages of trauma responses as the 6 “F”s: Freeze, Flight, Fight, Fright, Flag, and Faint.

What are the 7 steps in managing stress? ›

7 Ways to Manage Your Stress
  • Track your stressors. Use a journal to identify which situations create the most stress and how you respond to them. ...
  • Set limits. ...
  • Tap into your support system. ...
  • Make one health-related commitment. ...
  • Manage your devices. ...
  • Enhance your sleep quality. ...
  • Seek additional help.
Jun 5, 2018

What is the first step in eliminating stress? ›

Try stretching or taking a hot shower. Regular physical activity can help prevent and manage stress. It also can help relax your muscles and improve your mood. Aim for two hours and 30 minutes a week of physical activity, exercising for at least 10 minutes at a time.

What are 7 physical signs of stress? ›

Headaches. Upset stomach, including diarrhea, constipation, and nausea. Aches, pains, and tense muscles. Chest pain and rapid heartbeat.

What causes a person to shut down emotionally? ›

Why People Emotionally Shut Down. Trauma, prolonged stress, anxiety, depression and grief all contribute to feeling emotionally shut down. Nemmers says medication, while lifesaving for many, can also trigger a side effect of emotional numbness.

What organs are affected by stress? ›

Stress affects all systems of the body including the musculoskeletal, respiratory, cardiovascular, endocrine, gastrointestinal, nervous, and reproductive systems. Our bodies are well equipped to handle stress in small doses, but when that stress becomes long-term or chronic, it can have serious effects on your body.

What is toxic stress? ›

Toxic stress response:

This is the body's response to lasting and serious stress, without enough support from a caregiver. When a child doesn't get the help he needs, his body can't turn off the stress response normally. This lasting stress can harm a child's body and brain and can cause lifelong health problems.

Which is most likely to cause a person the most chronic stress? ›

What causes chronic stress? Causes of chronic stress could include poverty, a dysfunctional marriage or family, or a deeply dissatisfying job. In today's hectic society, there are many possible sources. Chronic stress slowly drains a person's psychological resources and damages their brains and bodies.

What is the difference between stress and stress response? ›

Generally when we react, the situation that happened is not acknowledged (i.e. we habitually react). A stress response on the other hand, acknowledges what is happening in the present moment, allows the feelings/emotions to be there as well as develop tools to work with them.

What is the difference between stress and anxiety? ›

People under stress experience mental and physical symptoms, such as irritability, anger, fatigue, muscle pain, digestive troubles, and difficulty sleeping. Anxiety, on the other hand, is defined by persistent, excessive worries that don't go away even in the absence of a stressor.

What part of the brain controls stress response? ›

The amygdala is the brain structure that actually detects stress and tells the HPA axis to respond. It can detect both emotional and biological stressors. An emotional stressor is something in the environment that may cause you to feel scared, sad, or frustrated, like the bear.

What happens in the first stage of stress response? ›

Alarm reaction stage

Your heart rate increases, your adrenal gland releases cortisol (a stress hormone), and you receive a boost of adrenaline, which increases energy. This fight-or-flight response occurs in the alarm reaction stage.

What two important questions are you answering when you assess a stressful situation? ›

You typically reach the exhaustion stage when stress is extreme or prolonged. The two questions you are answering are, “Is this situation a threat to my well being?” and “Do I have the necessary resources to meet the challenge?”

What is Stage 3 in the stress response define? ›

3. Exhaustion. The final stress stage is exhaustion, which results from your body trying to combat stress for an extended period. Typically, in this stage you find yourself feeling run down and having far less energy than normal.

What is one of the major findings of Vaillant's Harvard Grant study? ›

According to The Atlantic, George Vaillant's main conclusion is that the warmth of relationships throughout life has the greatest positive impact on life satisfaction. Put differently, Vaillant says the study shows: "Happiness is love. Full stop."

What was the famous Harvard experiment? ›

Harvard human experiments, 1959–62

The unwitting undergraduates were submitted to what Murray called "vehement, sweeping and personally abusive" attacks. Specifically tailored assaults to their egos, cherished ideas, and beliefs were used to cause high levels of stress and distress.

What have studies shown about stress? ›

Chronic stress, or a constant stress experienced over a prolonged period of time, can contribute to long-term problems for heart and blood vessels. The consistent and ongoing increase in heart rate, and the elevated levels of stress hormones and of blood pressure, can take a toll on the body.

What was the main purpose of the Harvard Grant Study? ›

Grant. It began with 268 men who were sophomores at Harvard between 1939 and 1944. Bock wanted to get away from medicine's tendency to focus on the small, specialized and sickly. He wanted to study successful and normal men, to see what makes a good life and maybe even decipher a general recipe for success.

What did the Grant Study what did they observe? ›

The Grants study the evolution of Darwin's finches on the Galapagos Islands. The birds have been named for Darwin, in part, because he later theorized that the 13 distinct species were all descendants of a common ancestor.

What was the key finding of 75 year old Harvard Grant Study? ›

Social relationships, or the lack thereof, constitute a major risk factor for health —rivaling the effect of well established risk factors such as blood pressure, blood lipids, obesity and physical activity.”

What is the most important thing to get into Harvard? ›

Harvard is looking for students with “growth and potential”.

To get accepted into Harvard, students must show commitment to excellence through “interests and activities,” have upstanding “character and personality,” and “contribute to Harvard's community.”

What is an example Harvard statement of purpose? ›

Statement Of Purpose. My aspiration to work at the frontiers of scientific research leads me to apply to your university. I believe that a comprehensive knowledge and a good grasp of fundamentals are essential for such a career.

What is the most famous unethical experiment? ›

In the Tuskegee syphilis experiment from 1932 to 1972, the United States Public Health Service contracted with the Tuskegee Institute for a long-term study of syphilis. During the study, more than 600 African-American men were studied who were not told they had syphilis.

What is the biggest experiment in the world? ›

The LHC is the largest experiment ever built on Earth. The inside of its 27-kilometer (17 mile) underground ring, located beneath the French-Swiss border near Geneva, emulates the conditions that existed fractions of a second after the Big Bang, the explosion that created the universe 13.7 billion years ago.

Who was the first black man to study at Harvard? ›

Harvard's first Black graduate, Richard T. Greener, went on to become the first Black professor at the University of South Carolina and dean of the Howard University School of Law. Born in Philadelphia in 1844, Richard T.

What is the relationship between stress and health? ›

Indeed, stress symptoms can affect your body, your thoughts and feelings, and your behavior. Being able to recognize common stress symptoms can help you manage them. Stress that's left unchecked can contribute to many health problems, such as high blood pressure, heart disease, obesity and diabetes.

What are 2 important facts about stress? ›

Stress affects everyone.

With chronic stress, those same lifesaving reactions in the body can disturb the immune, digestive, cardiovascular, sleep, and reproductive systems. Some people may experience mainly digestive symptoms, while others may have headaches, sleeplessness, sadness, anger, or irritability.

What are 2 important statistics facts about stress? ›

About 33 percent of people report feeling extreme stress. 77 percent of people experience stress that affects their physical health. 73 percent of people have stress that impacts their mental health. 48 percent of people have trouble sleeping because of stress.


1. How stress affects your brain - Madhumita Murgia
2. The Health Burden of Stress: What We Can Do About It
(Harvard T.H. Chan School of Public Health)
3. Harvard Public Health Magazine Extra: Stress & Health
(Harvard T.H. Chan School of Public Health)
4. 3. Toxic Stress Derails Healthy Development
(Center on the Developing Child at Harvard University)
5. The Stress Response- Fight or Flight
(learning junction)
6. Stress Science: Visualizing the Effects of Stress on the Human Body


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