Understanding The Fight Or Flight Response: A Guide For Therapists

The fight or flight response is one of the most widely recognized survival mechanisms in psychology.

For therapists, understanding this response is essential not only when working with anxiety disorders, but also when helping clients make sense of trauma-related reactions and automatic responses to perceived threat.

This article explores the purpose, function, and significance of the fight or flight response, drawing on contemporary understandings of threat responses and trauma.

What is the fight or flight response?

The fight or flight response is an automatic physiological reaction to an event that is perceived as stressful or frightening.

The perception of threat activates the sympathetic nervous system and triggers an acute stress response that prepares the body to fight or flee.

These responses are evolutionary adaptations that aim to increase the chances of survival in threatening situations. When an individual detects danger, the body releases adrenaline and initiates a series of changes that help prepare for action.

Walter Bradford Cannon (1915) originally described the fight or flight response after observing how animals reacted to threats. He noted that exposure to danger triggered the release of adrenaline (epinephrine), leading to increased heart rate, faster respiration, and other bodily changes that served emergency survival functions. These reactions happened automatically and helped the organism prepare for fighting or running.

Overly frequent, intense, or inappropriate activation of the fight or flight response is implicated in a range of clinical conditions, including many anxiety disorders. A helpful part of treatment for anxiety is an improved understanding of the purpose and function of the fight or flight response.

How the body changes during fight or flight

The fight or flight reaction is associated with activation of the sympathetic nervous system. The resulting chain reaction affects multiple body systems.

Cardiovascular changes

Heart rate increases, and coronary blood vessels dilate. Blood flow increases, making more oxygen and energy available to the heart. Blood vessels serving the muscles dilate, while blood vessels serving digestion constrict. This shunts blood toward skeletal muscles and the brain.

Clients may experience heart pounding or racing, feeling flushed or pale, or cold hands due to constriction of blood vessels in the skin.

Respiratory changes

The bronchi dilate and respiration rate increases. Quicker breathing takes in more oxygen to power the muscles. This makes the body more able to fight or run away. If the additional oxygen is not used through physical activity, individuals may begin to feel dizzy or lightheaded.

Metabolic changes

The liver increases the conversion of glycogen to glucose. This increases the availability of glucose in skeletal muscle and brain cells, providing fuel for rapid action.

Muscular changes

Muscles throughout the body tense in preparation for action. Muscles may also shake or tremble, particularly if the person remains still, as a way of staying “ready for action.”

Digestive changes

Blood is diverted away from the digestive system.

Individuals may experience dry mouth, nausea, or “butterflies” in the stomach.

Digestion effectively shuts down as energy is redirected toward systems needed for immediate survival.

Sensory and cognitive changes

The pupils dilate, allowing in more light and improving visual acuity. Vision can become acute, and some individuals notice tunnel vision or a sense that vision has become sharper.

Automatic psychological reactions include a quickening of thought and an attentional focus on salient targets such as the source of threat and potential avenues for escape. Thoughts may race as quicker thinking helps individuals evaluate danger and make rapid decisions. It can become difficult to concentrate on anything other than the danger or possible escape routes.

The psychological implications of fight or flight

The fight or flight response is not only physiological. It also influences attention, cognition, and behavior.

Strong feelings such as fear direct attention toward potential danger. Focus then narrows to the threat, opportunities to escape, or ways to overcome the threat.

Other important psychological responses include the meaning given to bodily sensations associated with fight or flight. For example, clients with panic disorder often misinterpret fight or flight responses as signs of impending catastrophe. Thoughts such as “I’m having a heart attack” or “If this carries on I’ll go mad” may develop in response to normal physiological changes associated with threat activation. Similarly, clients with post-traumatic stress disorder (PTSD) may mistake the increased physiological arousal as an indicator that there is a current genuine threat present.

In light of this, many clients benefit from a deeper understanding of the fight or flight response because it can decatastrophize these experiences and help make sense of them.

Fight or flight within the wider defense cascade

Modern models suggest that fight and flight are only part of a broader range of automatic responses to threat. Schauer and Elbert (2010) describe an elaborated model of physiological, psychological, and behavioral responses to threats known as the defense cascade.

Individuals exposed to threat or trauma may move through a series of responses including:

• Freeze.

• Flight.

• Fight.

• Fright.

• Flag.

• Faint.

The freeze response is often an initial response to something frightening. Individuals may become still, watchful, and highly alert while assessing danger.

Flight involves attempts to flee, escape, avoid, or run away. The body prepares for physical activity through the release of adrenaline, increased heart rate, faster breathing, and muscle tension.

Fight involves confronting or overcoming an opponent. Sometimes physical confrontation occurs, while in other situations merely appearing aggressive may be enough to make an opponent back down.

In situations where escape is impossible, other responses may emerge, including dissociation, immobility, or reduced awareness of pain. Understanding this broader context can help therapists normalize reactions that clients may view as confusing, shameful, or evidence of personal failure.

Clinical implications for therapists

1. Anxiety disorders

Overly frequent or intense activation of the fight or flight response is implicated in many anxiety disorders. Some clients interpret bodily sensations as dangerous rather than understanding them as manifestations of a threat response.

Psychoeducation regarding the purpose and function of fight or flight can therefore be an important treatment component.

2. Panic disorder

Clients with panic attacks often misinterpret bodily sensations associated with fight or flight. Understanding that symptoms such as racing heart, dizziness, trembling, sweating, or breathlessness reflect a survival response rather than catastrophe can help challenge threatening interpretations.

3. Trauma and PTSD

Individuals who have experienced trauma may mistake physiological arousal as evidence that danger is currently present. Understanding the fight or flight response can help them feel safer and provide a framework for implementing relaxation and grounding strategies. Trauma survivors may also experience responses beyond fight or flight, including freezing, dissociation, appeasement, or emotional numbing.

4. Dissociation and the window of tolerance

The window of tolerance describes a range of emotional arousal within which individuals can comfortably experience, process, and integrate experiences.

When arousal rises above this window, individuals may become hyperaroused and experience intense anxiety or attempts to escape. When arousal falls below the window, individuals may experience numbness, disconnection, or dissociation. For clients affected by trauma, understanding the relationship between threat responses and their window of tolerance can provide a valuable organizing framework.

Tips for therapists introducing the fight or flight response

1. Discuss the function.

The key message is that these reactions prepare the body for action and survival.

2. Link symptoms to specific bodily systems.

Help clients understand why the heart races, muscles tense, breathing changes, and digestion slows when the response is triggered.

3. Explore clients’ interpretations of bodily sensations.

Misinterpretations often maintain anxiety and panic.

4. Normalize automatic threat responses.

Fight, flight, freeze, and related responses occur automatically and are not deliberate choices.

Conclusion

The fight or flight response is a survival system that coordinates physiological, cognitive, and behavioral changes in response to perceived danger.

For therapists, an understanding of this response can inform psychoeducation for clients experiencing anxiety, panic, trauma, and associated presentations. By helping clients understand that many distressing sensations are adaptive responses designed to promote survival, therapists can support greater understanding, reduced fear of symptoms, and engagement in treatment.

Frequently asked questions

What is the purpose of the fight or flight response?

The fight or flight response prepares the body to survive threatening situations by mobilizing energy and attention for fighting or escaping.

Why do clients experience physical symptoms during anxiety?

Many anxiety symptoms reflect activation of the sympathetic nervous system, including increased heart rate, faster breathing, muscle tension, sweating, and changes in digestion.

Is fight or flight only relevant to anxiety disorders?

No. The response is also relevant to trauma, PTSD, panic disorder, dissociation, and other conditions involving threat detection and physiological arousal.

How does fight or flight relate to trauma?

Trauma survivors may experience fight or flight reactions during traumatic events and afterward when reminders of danger activate their threat systems.

Why is psychoeducation about fight or flight useful?

Understanding the purpose and function of threat responses can reduce catastrophic interpretations of bodily sensations and help clients make sense of their experiences.

Key references

• Cannon, W. B. (1915). Bodily changes in pain, hunger, fear, and rage. New York: Appleton-Century-Crofts.

• Cannon, W. B. (1916). Bodily changes in pain, hunger, fear, and rage: An account of recent researches into the function of emotional excitement. D. Appleton.

• Schauer, M., & Elbert, T. (2010). Dissociation following traumatic stress. Journal of Psychology, 218, 109–127.