The fight, flight, or freeze response refers to involuntary physiological changes that happen in the body and mind when a person feels threatened. This response exists to keep people safe, preparing them to face, escape, or hide from danger.

However, people can experience this response whether the danger is real or not, which can lead to this response activating in situations where it is not necessary. People can also react to perceived threats in different ways, which is where the name “fight, flight, or freeze” comes from.

This article looks at the fight, flight, or freeze response in more detail, and provides examples of how it affects people. It also explores the lingering effects of stressful events and offers suggestions for coping.

Two people playing with a wire airplane and dragon against a blue background, to represent the fight or flight response.Share on Pinterest
Diane Durongpisitkul/Stocksy

The fight, flight, or freeze response is how the body responds to perceived threats. It is involuntary and involves a number of physiological changes that help someone prepare to:

  • fight, or take action to eliminate the danger
  • flee, which involves escaping the danger
  • freeze, which involves becoming immobile

Some people also include a fourth option, fawn or appease, in this response. Fawning involves trying to please the person who represents a threat in an effort to prevent harm.

Another potential reaction is tonic immobility, which some refer to as “flop.” This involves becoming completely physically or mentally unresponsive. Fainting in response to fear is an example of the “flop” response.

Together, this makes up what scientists call the acute stress response.

An acute stress response causes the body’s autonomic nervous system (ANS) to activate. This is the part of the nervous system that controls rapid, unconscious responses, such as reflexes.

The ANS can send messages that tell the body to prepare for danger in different ways. If someone experiences either the fight or flight responses, they will develop:

  • Rapid breathing and heart rate: This allows the body to send more oxygenated blood to the muscles and brain, in case someone needs to take physical action to escape danger. This also causes an increase in blood pressure.
  • Flushed or pale skin: As the body redirects blood to key areas, a person may develop a paler face than usual, or it may alternate between pale and flushed.
  • Tense muscles: As the muscles prepare to move, they can become tense, which may cause shaking or trembling. Muscle tension can also create a constricted feeling in the throat, and result in a person’s voice becoming higher pitched.
  • Dilated pupils: The pupils dilate to allow more light into the eyes, which allows someone to see better and observe their surroundings.
  • Dry mouth: Constriction of the blood vessels around the mouth mean that the salivary glands temporarily stop producing saliva, causing a dry mouth.

A person in fight or flight may feel extremely alert, agitated, confrontational, or like they need to leave a room or location. A severe fight or flight response can become a panic attack. It can also trigger asthma attacks in people with the condition.

The freeze response involves a different physiological process than fight or flight. Research from 2015 describes it as “attentive immobility.” While the person who is “frozen” is extremely alert, they are also unable to move or take action against the danger. Freezing causes:

  • physical immobility
  • a drop in heart rate, rather than an increase
  • muscle tension

Why do some people freeze or ‘flop’?

While freezing might seem like a counterintuitive way to respond to danger, it serves a purpose, just as fight or flight does. Freezing may:

  • Prepare someone for action: A 2017 review suggests that freezing may function as a time for the brain to decide how to respond to the threat. In experiments where participants had more time to prepare to take action, a period of freezing was more common. In animal studies, scientists have observed that freezing enables animals to continue scanning the environment in order to decide what to do next.
  • Increase visual perception: A 2015 study argues that freezing is associated with a better perception of one’s surroundings. The researchers tested people’s reactions to shock and how this affected their ability to understand visual information. Those who froze had a better understanding of what they saw in low-quality or poorly defined images, and processed threat-relevant information faster.
  • Help someone hide: In some situations, being very still may keep a person safe from danger, or cause an attacker to lose interest. In animals, tonic immobility can be a last resort when fighting or fleeing have not worked, as many animals will not eat something that is dead.
  • Reduce the impact of the event: A 2017 article suggests that the freeze response may be related to dissociation. Dissociation is something that can occur when a person has a traumatic experience. It makes severely distressing events feel less real, causing a person to feel numb or detached. This may explain why the freeze response is more common in people with previous experiences of trauma.

Learn more about psychological trauma.

If a person is out running and suddenly encounters a large, snarling dog, this could activate the fight, flight, or freeze response. The person might:

  • fight, becoming aggressive or throwing an object at the dog
  • flee, increasing their jogging speed in order to escape
  • freeze, causing them to stop running
  • fawn by trying to calm the dog down
  • flop, or become temporarily unconscious

People can also respond this way to situations or people they feel stressed or anxious about, even if the experiences are not dangerous. For example, public speaking, job interviews, and exams can all trigger the stress response.

If someone has experienced trauma in the past, their acute stress response can become overactive, and respond to things that remind them of a previous event, or that they interpret as threatening.

For instance, if someone grew up in a neighborhood where there was frequent gunfire and then hears a car backfiring as an adult, they might:

  • become agitated or angry, as though ready for confrontation
  • search for a way to escape, even though they are safe
  • become still and silent
  • think of ways to appease someone with a gun
  • faint

This type of nervous system overactivity is a feature of post-traumatic stress disorder (PTSD).

The fight, flight, or freeze response is an important way for the body to protect itself. In situations that are dangerous, it can save someone’s life. However, if a person experiences it frequently due to events in their life, or due to stress or anxiety, it can take a toll.

To cope with the effects of the stress response, people can try:

  • Moving to a safe place: If possible, try to go somewhere that feels less threatening or overwhelming. This could mean going outside, finding somewhere quiet, or somewhere less crowded.
  • Slowing breathing: The stress response causes fast, shallow breathing. People can slow this down with breathing techniques. For example, diaphragmatic breathing can lead to a quieting or reversal of the stress response.
  • Moving around: Some people find physical activity helps with stress. For example, if someone feels restless or agitated, they might benefit from going for a walk or a run. Activities such as yoga can also help with slowing breathing down.
  • Seeking social support: If possible, ask for or accept help from trusted friends, family, or coworkers.

Learn five breathing exercises for stress and anxiety here.

It takes around 20–60 minutes for the body return to its normal state after the stress response becomes activated. Afterward, a person may feel tired, achy, or have some lingering anxiety. Generally, it is a good idea to do things that feel safe and restful during this time.

Self-care is important during times of stress. This may include:

  • eating regular, balanced, and nutritious meals
  • drinking enough water
  • taking breaks, especially from things that add to stress, such as work or watching the news
  • getting regular exercise
  • getting enough sleep
  • making time for relaxation and enjoyable activities
  • connecting with others

Sometimes, events that trigger the stress response are traumatic. This may cause a range of physical or emotional reactions that make it feel difficult to look after oneself. People who are traumatized can experience:

  • feelings of shock, anger, sadness, or fear
  • disbelief or denial
  • emptiness or numbness
  • difficulty sleeping or nightmares
  • changes in appetite and energy
  • physical symptoms, such as headaches, stomach problems, or body pains
  • worsening of mental or chronic health conditions
  • increased use of alcohol, tobacco, and other substances

If someone is struggling with these symptoms, they can seek support to help them process what happened and reduce the impact of stress.

Everyone recovers from frightening or stressful events at a different pace. If the effects of a stressful event do not improve on their own, though, it may help to speak with a doctor or therapist.

Chronic activation of the stress response has a negative effect on the body and can contribute to chronic pain, digestive conditions, hormone imbalances, and difficulty conceiving. So, it is beneficial for mental and physical health to address frequent stress.

There are specific therapies that can help people who have experienced trauma or who have PTSD, as well as treatments for those with anxiety or high stress levels.

Learn about the different types of therapy here.

The fight, flight, or freeze response enables a person to cope with perceived threats. It activates the ANS, which causes involuntary changes such as an increased heart rate, rapid breathing, and muscle tension.

People in fight or flight tend to take action to avoid or confront danger, while those in “freeze” become immobile. Fawning or flopping can also be part of the stress response.

There is no right or wrong way to behave during the fight, flight, or freeze response. However, there are things people can do to reverse the response, calm down, and address its impact. If someone suspects a recent or past experience is having a lasting effect on them, they can seek support from a mental health professional.