Trauma and PTSD

The Neurobiology of Traumatic Fight/Flight/Freeze

The neurobiology of trauma and the fight/flight/freeze response

This is an updated version of a post on the fight/flight/freeze response from a couple of years ago.


A few years ago I was thinking about applying for a nursing job with a sexual assault support team, so I decided to learn more about the body’s biological fight/flight/freeze response to trauma.  What I found out was really interesting, so I thought I’d share.

The amygdala’s response

The amygdala is a primitive part of the brain that processes emotional reactions and memories related to threats.  The amygdala automatically reacts to rape as a potentially life-threatening event; it doesn’t matter whether the victim knows the perpetrator or not.  

It triggers the activation of the fight/flight/freeze response. This stimulates the hypothalamic-pituitary-adrenal (HPA) axis, which connects the brain and the adrenal glands. This leads to the release of a rush of hormones, including cortisol, norepinephrine, endogenous opioids, and oxytocin.

The traumatic hormone soup

The prefrontal cortex, the most evolutionarily advanced part of the brain, takes a backseat when the amygdala starts going full-throttle.  Norepinephrine starts flooding the prefrontal cortex. This causes logical reasoning, rational decision-making, and higher-level regulation of thoughts and emotions to all go right out the window.

The body naturally makes its own opioids, including endorphins, which it releases in threatening situations. It makes sense if you’re a caveman running from a tiger and the amygdala doesn’t want pain slowing you down.  This also tends to flatten people’s affect (facial expression of emotions) for several days. This can appear strange for people who think that a victim “should” have a visible emotional reaction to trauma.

Oxytocin tends to be best known for its role in pregnancy and mother-infant bonding, but it also counteracts pain.  It’s released as part of the hormone soup of trauma, and one of the odd effects is that it can cause victims to laugh while recounting the traumatic events.

Tonic immobility

The freeze part of the fight/flight/freeze response is impacted by cortisol and the simultaneous activation of both the sympathetic and parasympathetic nervous system.  One source said up to 50% of rape victims experience “tonic immobility”, which involves muscle paralysis while still maintaining awareness.  Another source said that this happens in up to 85% of victims. This response tends to be more likely in people who’ve previously been assaulted.

The prevalence of this response is totally contrary to the popular notion that people “should” fight back when being assaulted. Tonic immobility isn’t voluntary; it’s the same instinct as an animal “playing dead.”

Critical incident amnesia

Another effect is “critical incident amnesia.” The brain encodes the events as they’re occurring, but those memories aren’t immediately accessible.  Recall begins to improve after the first night of sleep post-incident, but it’s only after the second night of sleep that the memories become fully accessible.  

Alcohol can impair the encoding of contextual details in memory. However, the sensory information still gets encoded (particularly smell, due to the location of the olfactory bulb in the brain).  Those sensory details can serve as a gateway to access more memories of the event.

There’s no “right” way to react

Society has so many expectations of how people “should” look/feel/act.  People think that they can predict how someone “should” “rationally” react to trauma.  But that caveman amygdala has been around a heck of a lot longer than all these “shoulds” and rationality. When it’s in the driver’s seat slamming on the gas of the fight/flight/freeze response, it’s doing its own thing.  

What people “should” do, including police and judges, is drop the victim blaming and educate themselves.

Sources

cover of PTSD Treatment Options: An Overview from Mental Health @ Home

The MH@H Store has a mini e-book on PTSD Treatment Options: An Overview that covers a number of evidence-based therapies for PTSD.  It’s also available as part of the Therapy Mini-Ebook Collection.

The blog index includes s list of posts related to trauma.

43 thoughts on “The Neurobiology of Traumatic Fight/Flight/Freeze”

  1. You never know how your are going to react until it happens. My reaction both during and after was completely different than what I would of thought it would of been. The rape crisis center was especially helpful in helping me understand my reactions weren’t as puzzling as they felt.

  2. Very informative! I totally agree with the concept that there’s no “right” way to react to any form of trauma. Whenever I watch those murder mystery shows like 48 Hours Mystery, and the police say, “Her reaction to her husband’s murder was very suspicous,” I’m sitting there thinking, “Um, maybe she was in shock?” You just can’t put a “normal” response on anything horrific. So I’m all like, “Show me some evidence that she’s the killer, because the way she reacted to his death tells me nothing.”

    I hope police know that fact you mentioned about rape victims’ memories not being fully returned for a day or so. I can’t imagine how frustrating it would be to not be fully heard because you didn’t know.

    Regarding rape, a really good, must-read document is the victim’s statement in the Brock Turner case. https://www.documentcloud.org/documents/2852615-Stanford-Victim-Letter-Impact-Statement-From.html

    Great post!!

      1. It sure is! Sorry… I hope I didn’t bring you down with it! 😮 I cried when I first read it! I really admire her attitude and her fortitude. She’s such a great role model, and I’d love for her story to be required reading for middle school students!

  3. After reading your post and learning so much your statement “What people “should” do, including police and judges, is educate themselves” was a fantastic way to end it as its horrible to assume that everyone should respond the same way to trauma. Thanks for sharing as I learnt a lot 🙂

    1. The info I was looking at was only talking about adults, but the machinery is the same in kids, and childhood trauma throws the whole sympathetic/parasympathetic nervous system balance out of whack. And trauma memories get stored in the amygdala until they can at some point be processed and shifted into other memory areas.

      1. Ok thank you. I’m just really interested

        It’s an area I really want to learn more on, I’m just no sure where to start. I learn bits and pieces here and there, but I want to know how it all works.

  4. Thanks for writing this..I struggle to accept with how my body reacted to my attack, my body went through fight/flight and freeze over and over before I eventually managed to dissociate .. as for my memories I still can’t recall the majority of it 2 years later, some things come back to me in my nightly nightmares but cause a trauma response when I’m awake so I think my brain tries to block it again instead of allowing me to process. It’s frightening and it’s exhausting. I want to get “better” so badly. Just wish my body and mind would let me. Xx

        1. I’m so glad you were able to this time. And something related another blogger and I have talked about before is that people can even have a physical sexual arousal response while being assaulted because the body is so hard-wired with how it deals with that kind of thing, and the voluntary control aspect gets knocked out of commission.

          1. Yeah I’ve heard that before. I didn’t get that, not that I recall anyway. I just beat myself up for fighting too hard causing lasting injuries, not getting away fast enough and then giving in because I was in too much pain. 😔 it’s relentless. I could maybe understand if id just had one reaction of of those reactions only happened the once but they didn’t. I fought with no conscious thought process, then I didn’t fight when I could of because of pain and fear etc etc… bloody hell, all coming out now sorry! This is why I read things like this to try and convince myself that all my reactions were normal. Xx

            1. It would be nice if people could react in a “normal” way to the most horrendously abnormal situations, but it seldom (if ever) works out that way. xo

    1. Sorry you are going through so much Delilah. My heart goes out to you reading this. I hope you find your way to healing. 💜

  5. I was on jury service a few years ago, where a young (15) girl had been raped by her uncle. Back in the confines of the deliberation room, all eleven other jury members raised the fact that she was giggling while giving her statement and when the defense barrister was questioning her.

    I’d said that for 1) she was giggling when they made her use correct anatomical language to describe where he touched her and what he did. She giggled so much when she said the word ‘penis’ that I almost giggled out loud with her. She also giggled when she was asked to use the same language he’d used when raping her i.e.” f*cking dirty little whore,” and worse.

    And 2) that the Oxytocin is known to make the victims laugh. They looked at me like I was crazy, and still spent hours going over the same thing. I was furious that they almost didn’t believe her, and although it was a dreadful case to sit through given my history, but I’m so glad I was there. The outcome of 10 years in jail wasn’t enough for the monster!

    1. Jury trials scare me for that very reason. There are a lot of ignorant people out there, and there won’t always be someone on the ball on the jury with them.

  6. Do you know why someone could possibly do what the perpetrator says when they are in a freeze state? This isn’t to accuse by the way – I just know that a lot of people feel it’s their fault when they are told they were frozen but they still “participated” so to speak.

    1. I think when the caveman brain is in survival mode like that, if there’s something other than freeze that it thinks will be most likely to ensure survival, it will make it happen, but the prefrontal cortex remains offline for logical decision-making.

  7. This…is something I really, really need so share with my best friend. She went through this and in a space that was thought to be safe, and probably recognize these reactions all too well 😔

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