Fight-Flight-Freeze: The Defense Cascade Explained

All people and most animals exhibit defensive, or fear-based behaviors that are designed to keep them safe in dangerous or traumatic situations. Everyone reacts to threats differently depending on the situation. For most people, these behaviors are observed as the fight, flight, and freeze response, together known as the defense cascade. Children and teens experience natural reactions to fear like anyone else. When children and teens experience constant or frequent exposure to fear or trauma, the area of their brain responsible for activating the defense cascade can be on permanent alert. Read on to learn more about fear reactions and teen responses.

The Defense Cascade

The Harvard Review of Psychiatry states that evolution has “endowed all humans with a continuum of innate, hardwired, automatically activated defense behaviors, termed the defense cascade.” The defense cascade follows this series of steps:

  • Arousal: Arousal is the point where a fear stimulus has aroused or activated the fear response. During this stage, the heart will start beating faster and the brain will begin firing and get ready to make decisions to get to safety.
  • Fight/Flight: The fight and flight reactions can happen together or separately, depending on the person, situation, and learned fear response outcomes. Some people are fairly consistent while others may react differently in different situations.
  • Freeze: There are several types of freezing. Freezing can be an initial fear response, just like fight or flight is. This response is the absence of flight or fight and can serve a legitimate purpose. For example, in threat situations, some people will freeze to go undetected. Other times freezing can occur if the person becomes immobile or is “caught” by their source of fear.
  • Tonic/collapsed/quiescent immobility: Immobility is the final step in the defense cascade, often related to the freeze response. There are several types of immobility. Tonic immobility means to be still and stiff. Collapsed is to collapse from fear or faint. Quiescent is quiet, healing immobility after the fear has passed.

It should be noted that though there is generally a chronological series the fear response follows, all people react differently. Children may react differently to adults, or change their normal responses as they grow up. There may be repeated responses to fear, meaning a person will be stuck repeating the same fear response due to trauma or a continued association with the same fear even in its absence.


When a person is experiencing a fight response to fear, they will fight against what is stimulating that response. This could mean verbally, physically, or some other form. Upon arousal, the heart will start beating faster, the muscles will tighten and be ready for action, and pain responses will be dulled as adrenaline kicks in.


The flight response to fear causes a person to attempt to run or flee the object or situation causing them distress. This often means a person will physically remove themselves from the situation and leave that fear to get to safety. Upon arousal, the heart will start pumping faster, the muscles will prepare to move quickly, and the body will be tense and alert to changes in the path and obstacles that will prevent them from getting away from that fear. Again, the brain will block pain and the body will run on heightened adrenaline to allow for a longer distance or a faster getaway.


The freeze response is the absence of fight or flight. Upon arousal, the heart will beat faster, but the body will remain frozen and unable to move in response to that intense fear. Some researchers point to freezing as mitigated fear since one will often stop to collect themselves. There are three types of freezing that make up the fear response:

  • Tonic Immobility: The heart rate remains fast and the muscles are frozen. The body has failed to react in a fight or flight response and the person can only freeze. Sometimes this works if freezing can help avoid detection, but this response is most often seen by those who are already captured by their fear, physically or otherwise.
  • Collapsed Immobility: This is a variant of tonic immobility. The heart rate slows, the skeletal muscles weaken, and a faint or collapse response will cause the person to be immobile. Many times this person has become unconscious due to fear.
  • Quiescent Immobility: This differs from tonic and collapsed immobility in the sense that the person is displaying complete inactivity in a peaceful or healing way. Sometimes the person is already captured by their fear, or they appear “zoned out” in an attempt to cope with that fear without being able to physically move or fight.

For more information on the fight, flight, freeze response in the brain, see Harvard Review of Psychiatry’s Figure 2.

All teens react differently to fear. Teen girls will react differently to different situations, especially if they have trauma or mental health concerns that drive their fear. Many children live in fear for much of their lives due to trauma or unsafe conditions they are unable to escape. When children grow up in this fear-driven way, they create unhealthy responses to general triggers and tend to make questionable choices. Many of these children will drive people away with unsafe or harmful choices that, in their minds, keep them safe, though this is far from reality. If your teen daughter suffers from trauma and an always-alert fight-flight-freeze response, call Havenwood Academy. We help teen girls understand their trauma, their fear, and meet them where they are at to help with rehabilitation. Our professional staff offers a myriad of therapies targeted at teens and can help your child. Call us today at (435) 586-2500. We want to help your daughter.


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