When Remembering Hurts: The Role of Memory in PTSD

What really happens in our mind when a traumatic memory suddenly returns to torment us? Why can some people overcome dramatic experiences while others remain prisoners of them for years? A new theory proposed by researchers at the University of Washington (USA) tries to answer these questions by changing the perspective on post-traumatic stress disorder (PTSD).

PTSD is a psychological condition that can develop after living through or witnessing a traumatic event. It manifests with intrusive memories, nightmares, anxiety, and avoidance of anything that reminds one of the trauma, interfering with daily life. Much attention in studies on this disorder has been placed on the initial encoding in memory, but the retrieval processes of memories after the traumatic event are probably equally important, if not more so. Understanding how these work could facilitate resilience and both natural and therapeutic recovery for people suffering from this disorder.

In the recent article published in Behaviour Research and Therapy, the research group proposes a new model called Dynamic Social Retrieval Theory (DSRT) that interprets PTSD as the result of a dynamic and social memory reactivation process. Thus, it would not be only the traumatic event itself that causes suffering, but the way memories of that event are continuously recalled, modified, and consolidated over time—through thoughts, conversations, images, social, and cultural interactions.

Better to remember or forget?

“A memory is not like a Polaroid photo: you put it in a drawer and then take it out again,” explains Andrea Stocco, professor of neuroscience at the University of Washington and co-author of the paper. “The intuitive idea of how intrusive memory in PTSD works is that these Polaroids keep coming out of the drawer even if we don’t want to open it, but that’s not the case: memories are formed and then transformed; they are never just taken out of the drawer, they are relieved by the brain and therefore continuously modified.”

There is also another element to consider: the cellular renewal of our neurons, according to Stocco: “Someone who experienced trauma twenty years ago still remembers it very well after two decades, but in their brain, there is no longer a single neuron that originally encoded that memory, which is still there.” Indeed, after 20 years memory circuits are “completely different because in the meantime some things have been forgotten, others that were not there have been inserted into memory. This is important to understand not only how memory works in PTSD after many years but also the trajectory of therapeutic recovery for people who suffer from it.”

In the DSRT model proposed by Stocco and colleagues, every activation of memory is a “retrieval” event, that is, a recall that changes neuronal connections and influences what we remember in the future. The memory of the traumatic event, they explain in the paper, does not remain stationary in the brain but is continuously reorganized depending on the emotional and social context in which it is recalled. Forgetting, often seen as a loss, is in this perspective an adaptive function: a way the brain uses to reduce competition between memories and protect mental health.

A central aspect emerging from research is the role of the social dimension. Indeed, people with PTSD can be exposed to traumatic memory retrieval events that take many forms: conversations with friends and loved ones, interactions on social media, intentional recall, spontaneous thoughts, reliving with or without stimuli, and avoidance of traumatic reminders. It is also for this reason that experiences with a strong interpersonal component, such as violence or war, tend to leave deeper marks.

From theory to clinical practice

Although, as Andrea Stocco says, “many reviewers of the article were skeptical because they argued we were underestimating the role of stress or departing from the physiological basis of reinforcement learning,” the possible therapeutic implications of the new model proposed by the University of Washington team are significant. Framing PTSD as a memory disorder opens new avenues for intervening in the processes of recall and memory consolidation.

To explain better, the researcher cites an experiment conducted by one of his students: “We induced small controlled traumatic memories in healthy volunteers by asking them to rate the emotional intensity of negative and violent images. After a few days, some people said they continued to think, for example, of the image of a child with a facial deformity.” So it was not a trauma like suffering an assault, but it was enough to produce a small clinical effect.

The student then applied a memory model used in their laboratory based on the so-called spacing effect, which normally indicates which time intervals maximize memory. “We simply inverted the equation,” says Stocco, “asking ourselves: what is instead the interval that minimizes the possibility of remembering these images?” The result was counterintuitive: presenting the stimuli all at once, without intervals, drastically reduces intrusive effects. “Those who saw the images one after the other had almost no intrusive memories; those who saw them spaced out even had nightmares.”

However, this is exactly the opposite of what is done in therapy to treat PTSD, says Stocco: “If a person has experienced trauma, it is recommended to take a break period, then start spaced sessions of one or two weeks, and so forth. But with these spaces, you are doing exactly what educators tell you to do when studying: don’t study everything at once, and in truth, in this case, it is the best thing because you don’t want to remember it.” This observation could have practical implications in situations where trauma exposure is inevitable, such as firefighters or military personnel.

Trauma as a process, not only an event

In practice, the new theory proposed by the University of Washington research group suggests interpreting trauma not only as an “event” but also as a “process.” It would not only be what happened that defines our suffering but also how and when we remember or tell about it. And it is precisely in this dynamic—made of memories that light up, go out, and recombine—that the possibility of healing plays out.

However, it is important to keep in mind, concludes Stocco, that “the memory of a traumatic event is not dysfunctional in itself; it has an evolutionary function: it serves to remind us of danger and to avoid it in the future. But if we continuously reactivate it uncontrollably, it can become pathological.” This seems to be confirmed also by feedback received after the paper's publication, most of which was supportive. “We received various emails from researchers and clinical professionals who said they felt very comforted by our studies.”

Clinical implications therefore highlight the importance of daily life retrieval for people with PTSD, taking into account social interactions and cultural messages, as well as in therapeutic relationships to shape the long-term nature of memory and help those who survive a traumatic event to thrive.