Methodological and Therapeutic Implications of Studying Intrusive Memories in Non-Clinical Populations
Plimpton, Benjamin Cope
Intrusive memories (IMs) are repetitive, unwanted memories, characterised by their disruptiveness and often distressing content. They are most widely known as a feature of clinical conditions such as depression and post-traumatic stress disorder (PTSD), but have also been shown to occur in non-clinical populations. The majority of research on naturally occurring IMs has recruited clinical populations, and relied on questionnaires and interviews (i.e. retrospective reports). Most research with non-clinical populations has focused on analogue IMs that are induced following exposure to distressing film content (the so call “trauma film paradigm”), which participants are then asked to record in a simple diary. The principal aim of the present thesis was to develop diary and laboratory methods –previously used to research Involuntary Autobiographical Memories (IAMs) – and apply them to the study of naturally occurring and analogue IMs in non-clinical populations. These methods have proven useful for understanding the frequency, phenomenology and triggers of IAMs, and exploration of these variables with regard to IMs was another key aim of the present thesis. A final aim was to examine the therapeutic benefit of interacting with the content of IMs using these methods. Overall, results suggest that IMs in non-clinical populations are common and frequent. This was clearly demonstrated by the results of an initial online questionnaire (Study 1) in a general student population, and further supported by a naturalistic diary study (Study 2) which showed the frequency of IMs to be comparable to some retrospective studies in clinical populations. Finally, results of two studies using a novel laboratory method (Studies 3a and 3b), showed that it is possible to capture naturally occurring IMs reported by non-clinical participants under controlled conditions. The triggers for naturalistic IMs show some key similarities with IAMs. For example, the IMs captured under laboratory conditions in Studies 3a and 3b were highly susceptible to verbal cuing, as is the case with IAMs. Furthermore, personalisation of those verbal cues (based on an IM reported at screening) resulted in a greater frequency of reported IMs than was the case with non-personalised cues in Study 3b. Results also suggest some key differences in the triggers for naturalistic IMs, analogue IMs, and IAMs. For all three types of cognition, environmental triggers were the most frequently reported, but analogue IMs registered a slightly higher proportion of ‘no-trigger’ reports. In addition, results suggest that writing about and rating naturalistic IMs in the lab can yield differences in subsequent diary reports of abstract/verbal versus sensory/perceptual triggers, with in-person disclosure resulting in relatively equal proportions of each trigger-type (similar to IAMs) and non-disclosure resulting in many more abstract/verbal trigger reports. By contrast, analogue IMs consistently showed a significantly higher proportion of sensory/perceptual riggers. These findings have implications for theoretical understanding of the relationship of analogue IMs to naturalistic IMs, as well as the relationship of the latter to IAMs. Finally, results suggest that in-person disclosure of IMs may have the greatest therapeutic benefit, but that this may be augmented by a future oriented task such as keeping a diary of involuntary prospective memories. These results, however, differed from participants’ subjective assessment, suggesting that both objective and subjective measures are important for assessing the impact of any intervention.
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