Facing extreme danger, are you ‘wired’ to fight or take flight?

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Any veteran of a grade school science class learned this: animals (including humans) have an intrinsic ability to instantly react to danger. This “fight or flight” reaction means we are wired to either run away or fight off a threat. Mass shootings, airport bombings and other violent events have people pondering their own ability to survive these adrenaline-filled moments.

Consider the recent mass shooting at Marjory Stoneman Douglas High School in Parkland, Fla. In the aftermath of the tragedy that left 17 people dead, intense scrutiny was aimed at school resource deputy Scot Peterson, who stayed outside the building during the shooting — rather than rush in to intervene.  The deputy later resigned, as his inaction drew public scorn and accusations of cowardice. At the height of it, President Trump lashed out at the deputy, promising that in the same situation he would have rushed into the building, even if unarmed.

It is, of course, easy to sit back in the days following one of these horrific events and make such brave proclamations. It is another thing entirely to actually rush into a life-threatening situation. Indeed, “fight or flight” is much more complicated than grade-school biology taught us. And sometimes, this heightened state can go very wrong. A paper by Australian researchers illustrates one example:

Jeremy, a soldier in the 2003 Iraq war, was “constantly on the lookout for ‘trouble’ and…he often found it. He described a number of physical altercations—he had attacked other men on the basis of perceived provocation—that had occurred over the last 12 months.” In fact, all these incidents happened after he left the military. One recent altercation took place in a therapist’s office. But his responses developed as if he were still at war.

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Former school resource deputy Scot Peterson. Image credit: Broward County Public Schools.

The researchers, led by University of Sydney psychiatrist Kasia Kozlowska, looked at how people really react in the face of danger, whether real or perceived. To them, “fight or flight” was an outdated term that was more applicable to animals than to humans. Preferring the term “defense cascade,” the team observed from psychiatric patient records that human “defense cascade” models were more complex, “because humans make subjective representations of body states and endow their experiences with meaning, and because humans use their minds to create internally generated representations of threat.”


This does make our responses more complicated, because more recently evolved neuronal networks in the cortex interact with the genes and evolutionarily “older” circuits that all come together to react to extreme emotional states (like fear).

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The “fight or flight” reaction also leaves out another type of reaction: collapsed immobility, or freezing. In a previous Genetic Literacy Project report, we reviewed research by Joseph LeDoux, a neuroscientist at New York University who has been studying the freeze reaction. Kozlowska and her team, meanwhile, detailed this reaction, which includes fainting as well as freezing in place, and showed how nerve cells connecting the amygdala (which houses emotional memories), hypothalamus (which coordinates physical responses) and periaqueductal gray matter (which controls pain, fear and anxiety reactions), all work to create this response (for better or worse).

Other scientists have found more genetic and physiological complexity behind “fight or flight” even among non-humans:

  • Biologists from the Chinese Ministry of Education, University of Shanghai and University of Neuchatel (Switzerland) found in Japanese flounder that the fish had distinct personalities that determine whether they “froze” or “fled,” and that an acute stress created unique metabolic and physiological changes depending on this personality. So, if a “shy” fish was confronted, its metabolic changes resulted in a “freeze” reaction, while a “bold” fish had changes that produce a “fight or flight” reaction.
  • University of Maastricht researchers found that dopamine, which directs a number of cortical and physical reactions to extreme stress, is often controlled by a number of single nucleotide variations, as well as rearing conditions and personality types. This meant that other personal factors, in addition to the stress itself, all were factors determining how a person reacted to acute, extreme stress.
  • “Fight or flight” reactions can also be controlled, at least in humans. A group from Massachusetts General Hospital and Beth Israel Deaconess Medical Center found that meditation can trigger genes that regulate energy metabolism, mitochondrial function, insulin secretion, and telomere maintenance, in the opposite direction from “fight or flight,” thus creating a more relaxed state.

Humans (and apparently Japanese flounder) have more complex reactions to acute stress than previously thought, and (for humans) can be trained to handle reactions to these occurrences. But as war veterans and other survivors of attack situations have shown, we can over-react, as well.


Andrew Porterfield is a writer and editor, and has worked with numerous academic institutions, companies and non-profits in the life sciences. BIO. Follow him on Twitter @AMPorterfield.

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