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.
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.
PTSD Treatment Options: An Overview, a mini-ebook that’s available from the MH@H Download Centre, covers a variety of evidence-based therapies for PTSD.