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Key Takeaways:

  • The fight-or-flight is a response to a stressful, dangerous, or life-threatening event.
  • A series of reactions in the body trigger physiological changes that make it possible for us to confront or flee from the danger.
  • The fight-or-flight response can be triggered excessively, in which case it should be managed and controlled.

Stressful situations will always be present in our lives. Whether stressing over looming work deadlines or worrying about paying rent on time, our bodies respond accordingly and produce stress hormones to help us cope. This process is often called the fight-or-flight response, and it is a reaction to our stressful environment that leads to several physiological changes. Here, we’ll detail what going into fight-or-flight mode really means, why we experience it, and its impact.

What is the Fight-or-Flight Response?

The fight-or-flight response, or the acute stress response, is a physiological reaction triggered by something stressful or otherwise threatening (mentally or physically). In its most basic sense, this response prompts the release of hormones that prepare your body to fight the threat or take flight and seek safety.

Why Do We Experience the Fight-or-Flight Response?

We experience the fight-or-flight response as a natural reaction to dangerous or otherwise stressful circumstances. Essentially, our body systems are at work to keep us alive in what we perceive as a life-threatening situation. Without consciously deciding what to do, the brain and body can observe what is going on and assess how you can best survive the event you are faced with.

The term “fight-or-flight” comes from an ingrained reaction that dates back to our oldest ancestors when confronted with danger in their environment. They had two options: to fight or to flee. In either scenario, the body prepares itself to deal with the situation at hand. This has been passed down and deeply ingrained into our bodily systems today to serve as a means of protection from threats, whether real or perceived.

What Happens During the Fight-or-Flight Response?

When dealing with acute stress, the nervous system is activated by a sudden flood of hormones. More specifically, the sympathetic nervous system, which is responsible for the physical changes you experience when confronted with a threat, is activated [*].

Once the danger has been perceived, several hormones are released into the bloodstream, including the following:

  • Corticotropin-releasing hormone (CRH). This reduces appetite and increases selective attention as well as anxiety. Once this happens, it triggers the release of the second hormone.
  • Adrenocorticotropic hormone (ACTH). ACTH acts as a signal for the adrenal glands on top of the kidneys to release the stress hormone cortisol.
  • Cortisol. Cortisol increases alertness, energy, and immunity, all of which are necessary for the body to deal with an immediate threat.
  • Adrenaline. The adrenal glands are also responsible for releasing adrenaline, which increases heart rate and respiration.

This set of reactions results in several physiological changes, such as increased heart rate, blood pressure, and breathing rate. The body stays in this elevated state up to 20 to 60 minutes after the threat is gone [*].

Physical Changes During the Fight-or-Flight Response

You may wonder, “What does fight-or-flight feel like?” Several fight-or-flight response symptoms manifest physically during the response.

  • Heart rate and blood pressure. The first and most notable change is the increase in heart rate and blood pressure. Physically, this looks like quicker and heavier breathing, which aids in transporting oxygen and nutrients to your major muscle groups in case quick movement is needed.
  • Dilated pupils. During times of danger, your pupils will dilate to ensure you can see better. You become more observant, and your other senses are heightened to gather information about what’s going on around you [*].
  • Tense and trembling. The release of stress hormones can make you feel tense or twitchy as if your muscles are ready to move quickly at any moment.
  • Pale or flushed skin. During the fight-or-flight response, blood flow is redirected to the most important body parts that will prepare you for defense or escape. Your hands and feet might feel cool and clammy. Your face may also appear pale or flushed as blood and hormones rapidly circulate throughout the body. You may also have goosebumps.
  • Delayed pain. If you experience physical combat or collisions during the fight-or-flight response, then you may notice that any injuries you’ve sustained will only feel painful once you have returned to safety.
  • Memory loss or alteration. During stressful experiences, it is possible for your memories of the event to be altered. They can also be extraordinarily vivid or totally or partially blacked out.
  • Bladder control. In some cases, being in fight-or-flight mode can cause involuntary loss of control of the bladder.

All of these physical changes happen in the body as it tries to prioritize your safety. Anything that is not necessary for immediate survival, like digestion, reproductivity, tissue repair, and growth, becomes secondary for the time being. Your body’s energy is directed towards its most crucial functions to help you survive.

The Impact of Fight-or-Flight Response on Our Emotions and Cognitive Functions

To fully understand the impact of the fight-or-flight response on our emotions and cognitive functions, it helps to view the brain in two distinct parts: the “downstairs brain” and the “upstairs brain [*].”

The downstairs brain includes the brainstem and the limbic region. This part of the brain is responsible for basic bodily functions, such as breathing and digestion. It also controls reflexive responses, emotional reactivity, and, of course, the fight-or-flight response.

The upstairs brain includes the cerebral cortex, which controls decision-making, control over emotions and behavior, planning, executive functioning, and morality. The upstairs brain makes it possible to perform more complex tasks, such as balancing emotions, being flexible in our responses to events, making difficult decisions, and calming our fear.

Sometimes, the downstairs brain can interpret events incorrectly and conclude that danger is present, even when it isn’t. The downstairs brain then activates the fight-or-flight response despite there being no threat, and the upstairs brain shuts down temporarily. This results in our inability to use rational, problem-solving skills to make decisions about what to do with the situation. Fear is usually dialed up in response to the danger as the fear-calming ability of the cerebral cortex is halted.

Examples of the Fight-or-Flight Response

There are many examples of the fight-and-flight response as they are seen in everyday life situations.

  • Encountering an angry dog on your afternoon walk
  • Preparing for a big presentation at work or school
  • Being afraid of heights and going to a place with high altitude
  • Quickly moving out of the way of an oncoming vehicle
  • Feeling unsafe when walking down the street at night

These may be real or perceived threats, but they can trigger the fight-or-flight response, depending on the individual.

How to Manage and Control the Fight-or-Flight Response

The fight-or-flight response is normal and helpful during times of real danger. It is important to note that this is not the body’s normal state. However, fight-or-flight mode stays turned on when the brain incorrectly assesses threats constantly. Turning off the stress response to events that aren’t life-threatening can be difficult because they don’t have a clear delineation between what is real and perceived.

This results in a long-term activation of the stress response and too much exposure to stress hormones, which can disrupt the body’s regular processes and cause conditions such as anxiety or PTSD.

Managing and controlling the fight-or-flight response starts with acknowledging your stressors. In everyday life, this can be dealing with work, finances, kids, marriage, school, and so on. How you interpret these aspects of life can affect your body’s reaction to them, including whether fight-or-flight mode will be activated.

Once you have acknowledged your stressors, take note of how you react to them. Consider looking beyond your stressors when you feel yourself getting worked up in response to something that isn’t a life-threatening threat or danger. There are different ways to slow down and manage your stress, including eliminating the stressors (if possible), getting social support, maintaining good nutrition, practicing relaxation techniques, getting enough sleep, and exercising.

If you are struggling with controlling your fight-and-flight response, it may be prudent to seek a licensed professional's help to manage your stress.

Frequently Asked Questions

Here are some common questions that are often asked about the fight or flight response.

Can the fight or flight response be triggered by non-threatening situations?

Yes, it can. Depending on how an individual responds to stress, the fight-or-flight response can be overactive. This occurs when non-threatening situations trigger the reaction often. Such reactions are more common in people who have experienced anxiety and trauma.

Are there individual differences in how people experience the fight or flight response?

There may be differences in how people experience the fight or flight response, mainly in what triggers it. But the symptoms are mostly the same.

Are there other responses besides fight or flight?

There are other responses aside from fight or flight. They are the freeze and fawn responses.

The freeze response causes people to feel stuck and unable to proceed to fight or flight reactions. Symptoms of this response include feeling stiff and numb, decreased heart rate, pale skin, and a sense of dread.

The fawn response occurs after an unsuccessful fight, flight, or freeze response. This is more common in people who grew up in abusive situations. Signs of a fawn response include being overly helpful, over-agreement, and prioritizing someone else’s comfort or happiness.

The Bottom Line

The fight-or-flight response is necessary and extremely useful in truly life-threatening situations. However, we should pay attention to our flight-or-fight responses and assess whether they are being activated too often in everyday scenarios. This can commonly happen, and it may cause problems like anxiety.

If you often feel anxious from an overly active fight-or-flight response, then practical and accessible exercises like anxiety worksheets may help you regulate it. Lastly, it may also be beneficial to seek help from a professional when such issues arise.


  1. Chu B, Marawaha K, Sanvictores T, et al. Physiology, Stress Reaction. 12 September 2022.
  2. Gordon R, Gwathmey J, Xie L. Autonomic and endocrine control of cardiovascular function. 26 April 2015.
  3. Chen Y and Lyga J. Brain-Skin Connection: Stress, Inflammation and Skin Aging. 2014.
  4. Pace, K. Understanding the "upstairs" and "downstairs" brain. 5 January 2016.

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