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Why Do Flashbacks Happen?


Trauma symptoms are really strange to most people, especially to someone having to deal with them.  Understanding why they’re happening is a good first step to fighting the stigma of PTSD.  Flashbacks, hypervigilance and avoidance have everything to do with how we experience and store a traumatic event.

Non-Trauma Memory storage

Basically, when something manageable happens our brain can process the memory and store it in a meaningful way, like putting away groceries—we take things out of the grocery bag (the memory) and for each item, categorize and store like with like.

For example, imagining a grocery trip, you may think of someone else who was there, your comparing prices and couponing, and the process of checking out.  These associations go into corresponding memory networks so they can be retrieved in an organized manner.  Later, if you’re planning more errands for the week, you might think, “at least I already went to the grocery,” or “I forgot to buy chips.” In either case, adaptively stored information was accessible to you in a helpful way, and useless information, such as the shirt color of the person in front of you in line, was discarded.

Trauma Memory storage

However, a traumatic event is too much to process, so it gets stored without proper processing, with all the unpleasant sensations that came with it.  So in our grocery analogy, instead of neatly putting away canned goods with other canned goods, frozen things in the freezer, etc, your overwhelmed brain can’t process the memory in an organized way, scoops the whole thing up and crams it in a cabinet, slams the door shut to deal with it all later, and everything inside is just waiting to fall on your head the next time you open that door.

For a mild example, think of a memory from your childhood that still stings when you bring it up.  It can be something you did or was done to you, but when you imagine it, you still cringe. It’s not actually helpful for the memory to be that vivid, and for your emotions to be that raw when you think about it.

What are trauma symptoms?

Traumatic memories are really painful to encounter due to their unprocessed nature.  When the brain goes to access the “cabinet,” because there is helpful information somewhere in there, everything pours out at once.

Hypervigilance: Your brain will be wary of that event happening again.  However, since it hasn’t yet sorted out the true source of the trauma, anything that even remotely resembles the circumstances of the event is now cause for an intense reaction, ranging from being jumpy to a full-blown panic attack. So any smell, sound, sight, body position that is associated with the event is cause for alarm, and you are in constant defense mode.

Avoidance For our groceries analogy, let’s say the thing that overwhelmed you was a pungent smell coming out of the grocery bag.  It was too much to deal with, so now all of the groceries are in the cabinet, and you don’t actually know what the source of the smell is.  You do, however, know that whenever you open that cabinet door all that stuff falls on your head.  What your brain will do is instruct you to avoid anything that is associated with whatever might have been in that bag.  A traumatized person might avoid a song he was listening to when an explosion happened, or a street she was on when she was assaulted, as though avoiding these things will prevent the event from happening again.  The brain hasn’t been able to process what actually was and was not harmful, so everything that was in that grocery bag of the event has been marked “Danger: Avoid.”

Flashbacks: Your brain will want to rehearse for future scenarios so that it will be better prepared.  This is the reason behind the reliving phenomenon, which is what’s happening when someone is having nightmares, flash backs or intrusive thoughts of the event. However, anytime you get near that cabinet door, all of that stuff in the cabinet comes tumbling onto your head.  Unlike your organized memory of grocery shopping, which you can access in a controlled, and therefore helpful way, any attempt to access the traumatic event is overwhelmingly unhelpful.

Disassociation: Let’s say you weren’t able to get away from the traumatic situation, to fight or to flee.  Your mind may have disengaged to prevent you from experiencing further harm.  Like with the rest of the symptoms, though, it can’t distinguish between what was actually traumatic and what was just there, so everything that was in that bag is now a cue to disconnect.

Trauma therapy is a way to unpack the cabinet, sort through everything, throw out the useless stuff and organize the needed stuff.  When things are processed in a healthy way, we can integrate the trauma into our other lessons and memories, and continue to live our lives.

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Why Do Flashbacks Happen?

Sara Staggs, LICSW, MPH

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APA Reference
Staggs, S. (2013). Why Do Flashbacks Happen?. Psych Central. Retrieved on November 29, 2020, from


Last updated: 4 Nov 2013
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