New scientific research from the University of Technology Sydney will aim at boosting mental health options by uncovering more about the role of intrusive memories and unhealthy types of rumination in those suffering from depression.

The hope is that these studies will help build a better treatment protocol for depression in a clinical setting by looking at the impact of intrusive memories — effectively memories that spring to mind unbidden — which have predominantly been studied in relation to post-traumatic stress disorder (PTSD).

Adele Stavropoulos of the Graduate School of Health at the University of Technology Sydney was the first author of a soon-to-be-published research paper1 on how people ruminate on events that trigger negative moods, and how this influences the intrusive memories they experience afterwards.

Stavropoulos has also commenced further research expanding the initial paper, which looked at intrusive memories of study participants in the lab, and seeing how intrusive memories work for those suffering from depression in a clinical setting.

“The current treatment protocols for depression don’t specifically target intrusive memories even though there’s some research that they’re involved in the maintenance of the disorder. So we need treatment approaches for this construct in depression and that’s what we’re investigating at the moment,” she told Lab Down Under.

Shifting attention from PTSD

The studies will fill a gap caused by a focus of intrusive memory research on PTSD, despite the fact that these types of memories also occur across a broader range of psychological disorders including depression.

“Intrusive memories are very salient. A lot of people know about them anecdotally about war veterans having those flashbacks, so I think it has gained a lot of attention in PTSD. Now that we’re starting to do a bit more research, we’re seeing that we can have intrusive memories about lots of different events,” Stavropoulos said.

Intrusive memories by themselves are normal, simply being short-lived memories which pop into a person’s head either out of the blue or after being triggered by certain events.

“Intrusive memories don’t just have to be traumatic ones. They can be things like negative or even positive life events. In depression, they tend to be things like interpersonal problems or grief or loss which are often linked to the onset of the disorder,” Stavropoulos said.

Intrusive memories can produce worsening symptoms for depression thanks to rumination, or over-dwelling on a certain topic, however. The two can amplify each other, with intrusive memories triggering rumination and vice versa.

It’s all about the method

Stavropoulos told Lab Down Under that rumination wasn’t necessarily harmful – that it helped people to process emotional events and to problem solve. Whether rumination was maladaptive, i.e. more harmful than helpful, depended not on the length of time, how often, or the content of the thoughts but on the method by which an individual ruminated, called the processing mode.

These processing modes are divided into two categories: abstract analytic and concrete experiential.

In abstract processing, an individual thinks about a topic in a general way, focusing on the causes or consequences of an event and predominantly considering the past and future. Examples include someone viewing themselves as a failure or that they are incompetent at their job.

Concrete processing, on the other hand, sees an individual thinking about specific details and focusing on the present. For instance, someone could be pondering the embarrassment surrounding a recent event where they sent the wrong email to someone at work.

Stavropoulos said that the abstract mode of thinking was less helpful because it used over-generalised memories that lacked specific details which made it difficult for an individual to mentally process a particular event.

“The thoughts are not detailed and we’re not contextualising them. We’re not putting them into a particular time and place, so it’s hard to actually problem solve or think about the event in a more adaptive way. That can leave the concerns unresolved and it can actually just trigger a cycle of further rumination where we get stuck in a loop. It can also exacerbate distress and other symptoms,” she said.

These aren’t the results you’re looking for

In her initial study, Stavropoulos examined intrusive memories in 120 participants after they experienced a negative mood by watching a five-minute clip from the 2008 World War Two film, The Boy in the Striped Pyjamas, in which a young boy dies while his parents attempt to save him.

With 40 participants chosen as a control, the remaining 80 were split evenly and were asked to write an essay over 15-minutes using either abstract or concrete processing modes. Those writing in the abstract mode were asked about the general causes and consequences of the film clip and what World War Two meant for society. The concrete group had to write about the moment-to-moment experience they felt when watching the clip including their emotions, thoughts and physical sensations.

Stavropoulos hypothesised that the 40 participants in the abstract study would experience more intrusive memories than the concrete group and the control, following the results of prior research papers. However this was not the case with the study finding no difference between the abstract and concrete groups in the intrusive memories experienced.

“That was surprising. It was contradictory to the other research that we’d seen that had looked at processing mode and intrusions,” she said.

Methodological differences between this study and others meant that intrusive memories may have been brought on in stronger ways using self-referential or autobiographical events rather than film clips, Stavropoulos said. The rumination itself could also have interfered with the creation of intrusive memories in the short-term, she added.

“Because our study only measured intrusion for six hours, it’s possible that could have temporarily dampened the intrusive memories being formed. There’s other research which says that verbal processing such as rumination can lead to reduction in intrusions following a traumatic film, so that’s another explanation as well.”

Another surprise from the study was that those in the control group, who were given “distraction” tasks answering questions unrelated to the film clip, experienced higher levels of intrusive memories. Stavropoulos said this process could have accidentally acted as a form of thought suppression, which enhanced the likelihood of intrusive memories.

“We know that thought suppression is a very maladaptive emotion regulation strategy. If we try to push thoughts, memories or emotions away, they come back even stronger. We might have unintentionally gotten people to suppress their thoughts, which we know has a paradoxical rebound effect that it can cause memories to intrude more frequently.”

A future focused view

Despite these results, Stavropoulos has her eyes on her next research project looking at depression and intrusive memories in a clinical setting.

“We need to replicate the findings using idiographic approaches, so assessing rumination and intrusive memories in following actual spontaneously occurring events rather than something that’s been artificially done in the lab. At the moment, we’re doing something like that. We’re using experience sampling to assess people’s intrusive memories, rumination and other depression symptoms as they naturally occur in a clinical sample,” she said.

Lab Down Under will be eagerly following this research. While science doesn’t always go the way first hypothesised, the forward thinking focus of the researchers themselves can ensure continued clarification of the relationship between these processes and their role in depression.

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1 The influence of ruminative processing mode on the trajectory of intrusive memories following a negative mood induction , Adele Stavropoulos and David Berle, Journal of Behavior Therapy and Experimental Psychiatry, Volume 68, September 2020