Understanding Fight and Flight

fight and flight

The Fight and Flight response is part of our everyday understanding of our reaction to threat. However, even though common amongst our vocabulary, it is a fairly recent term.

Psychologist William James and physiologist Carl Lange coined the term ‘Fight and Flight’ in the 1920s as an evolutionary survival mechanism.   It is the body’s automatic response to danger and consists of a series of physical changes designed to assist you in overcoming the threat in question.

Although only coined in the 1920s this is an ancient response to physical threat which would have been essential to our prehistoric ancestors as they faced numerous dangers over a short life span.

Our perception of threat is largely an emotional one and it is now understood that emotions occur as a result of physiological reactions to events. Emotions are a complex reactionary pattern involving experiential, physiological and behavioural elements. [1]

  • Experiential – This refers to a stimulus or subjective experience, which triggers an emotion.
  • Physiological – Our physiological response to threat is the result of the autonomic nervous system’s reaction to the emotion triggered by the stimulus.
  • Behavioural – This is the actual response to, and expression of, the emotion.

The Fight and Flight response is an automatic response to danger, where strong emotion is invoked and the three elements above demonstrate how emotion is much greater than a mental state.


What is Fight & Flight?

Our prehistoric ancestors, and all mammals, have evolved to demonstrate the same automatic survival action of fight, flight and freeze.  Our bodies respond with one of the survival mechanisms depending on the threat in question:

  • Fight – You respond with Fight if you feel confident you can face or defeat the danger.
  • Flight – You respond with Flight if you cannot defeat the threat but feel you can run from it.
  • Freeze – If you cannot defeat the threat, and additionally cannot run from it the body has a third response which causes us to freeze. [2]

In our daily lives this response is activated either when in the face of imminent danger, such as at the top of a skyscraper, or as a result of psychological threat, such as a presentation at work.

Numerous physiological changes occur during a Fight and Flight response. [3] In response to acute stress the central nucleus of the amygdala (the part of your brain involved in fear learning and the activation of fear) it sends signals to the hypothalamus which in turn stimulates the autonomic nervous system. [4]  This system has two parts, the sympathetic and parasympathetic.  The parasympathetic instigates the Freeze response and the sympathetic nervous system stimulates the Fight and Flight response.

The sympathetic nervous system triggers the release of catecholamines, including adrenaline and noradrenaline, through the stimulation of the adrenal glands. [5]

The following changes happen automatically and unconsciously:[6]

  • Lungs: In order for more oxygen to enter the blood your breathing rate increases, and airways dilate.
  • Heart: For your oxygenated blood to reach your muscles quickly, to be used for energy, your heart beats faster.
  • Ears: Your hearing becomes more acute.
  • Eyes: Peripheral vision is heightened and your pupils dilate to help you see better.
  • Brain: Mental activity increases to allow for quick decision making.
  • Legs and arms: To help you run or fight sugar and fats are converted into energy and sent to major muscles.
  • Skin and sweat glands: Blood supplies diverted to the brain and muscles can cause skin to sweat, become cold, pale and for goosebumps to form.
  • Salivary glands: Your mouth becomes dry as salivary glands decrease function.
  • Gut muscles: As blood supply is decreased to the gut in preference of the brain and muscles digestion is affected and becomes
  • Liver and fat tissue: Glucose and fats are mobilised to fuel the muscles.


In a single situation a person may shift between Fight, Flight or Freeze spontaneously and the reaction depends on their subjective interpretation of the three emotional elements experience, physiology, and behaviour.

Although it is a physically uncomfortable response by priming your body for action, you are better prepared to survive, or perform under pressure.


When the Fight & Flight Response Becomes a Problem

The physiological reactions to the Fight and Flight response are often critical in surviving life-threatening situations.  However, individuals who have trauma disorders such as PTSD, major anxiety, panic disorder or acute stress may find that their nervous systems become over reactive to the presence of threat. The parasympathetic nervous system becomes dysregulated and will respond with an exaggerated, or inappropriate response to everyday situations which are incorrectly perceived as threatening.

The physiological arousal stimulated by the Fight and Flight response is draining on both body and mind and will result in acute emotional distress, a worsening of an individuals mental health, or even chronic physical ailments due to the toll stress takes on the body.

Coping with Fight and Flight

Understanding the body’s natural fight-or-flight response is the first step in healing from an overreactive stress response. Self-compassion is essential whilst gaining clarity over an individual’s personal life history and corresponding factors that cause Fight and Flight to be triggered.

The Fight and Flight response has been proven to be reduced with medications that alleviate anxiety. [7]  However, medication is not a guaranteed fix, and a combined therapeutic approach is the best way forward.  Somatic Experiencing Therapy[8],  focuses on the mind and body as one entity. It is extremely helpful in alleviating symptoms in those who have a heightened Fight and Flight response as this response is a combination of mental and physical and should be addressed as such.

Somatic experiencing allows people to explore traumatic events with awareness as to how the threat perception is played out in the body. This connects the mind and body whilst uncovering perceived fears, renegotiating reactions, and aiming to replace the stress with self-compassion and calm.

The stress response is a major topic within the growing field of health psychology. Through continued understanding of the fight-or-flight response, psychologists can help people live more productive, healthier, happier lives.

If you have a client, or know of someone who is struggling to heal from psychological trauma, reach out to us at Khiron Clinics. We believe that we can improve therapeutic outcomes and avoid misdiagnosis by providing an effective residential program and out-patient therapies addressing underlying psychological trauma. Allow us to help you find the path to realistic, long-lasting recovery. For information, call us today. UK: 020 3811 2575 (24 hours). USA: (866) 801 6184 (24 hours).


[1] “The Science Of Emotion: Exploring The Basics Of Emotional Psychology | UWA Online”. UWA Online, 2019, https://online.uwa.edu/news/emotional-psychology/.

[2] Schmidt, Norman B. et al. “Exploring Human Freeze Responses To A Threat Stressor”. Journal Of Behavior Therapy And Experimental Psychiatry, vol 39, no. 3, 2008, pp. 292-304. Elsevier BV, doi:10.1016/j.jbtep.2007.08.002. Accessed 12 May 2021.

[3] Hagenaars, Muriel A. et al. “Updating Freeze: Aligning Animal And Human Research”. Neuroscience & Biobehavioral Reviews, vol 47, 2014, pp. 165-176. Elsevier BV, doi:10.1016/j.neubiorev.2014.07.021. Accessed 12 May 2021.

[4] Robertson, David, and I Biaggioni. Primer On The Autonomic Nervous System. Elsevier/AP, 2012. Robertson, David, and I Biaggioni. Primer On The Autonomic Nervous System. Elsevier/AP, 2012.

[5] Heckman, William. “How The Fight and Flight Response Works – The American Institute Of Stress”. The American Institute Of Stress, 2021, https://www.stress.org/how-the-fight-or-flight-response-works.

[6] “What Is ‘Fight, Flight Or Freeze’?”. North West Boroughs Healthcare, 2021, https://www.nwbh.nhs.uk/healthandwellbeing/Pages/Fight-or-Flight.aspx.

[7] Milosevic, Irena. “Fight-or-flight response.” Phobias: The Psychology of Irrational Fear: The Psychology of Irrational Fear 196 (2015): 179

[8] Brom, Danny et al. “Somatic Experiencing For Posttraumatic Stress Disorder: A Randomized Controlled Outcome Study”. Journal Of Traumatic Stress, vol 30, no. 3, 2017, pp. 304-312. Wiley, doi:10.1002/jts.22189. Accessed 12 May 2021.