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Abstract

The objective of the study was to examine the frequency of intrusive memories in patients with Posttraumatic Stress Disorder (PTSD) through the use of two different Ambulatory Assessment methods (Time Based Assessment and Event Based Assessment). In addition, the predictors of the frequency of intrusive memories were assessed, as well as common triggering factors of intrusive memories.

The study sample comprised 50 subjects suffering from PTSD related to interpersonal violence. With the help of a 17-day smartphone-assessment the occurrence of intrusive memories and their triggers were assessed. Two different methods were applied: Time Based Assessment (TBA), in which participants were asked to answer one prompt every day and Event Based Assessment (EBA), in which participants were asked to enter any intrusive memory occurred into the smartphone.

The differences between the results of both methods were substantial: with TBA, on average 7.6 intrusive memories per day were captured, whereas EBA revealed a mean frequency of 1.4 intrusive memories per day. Common triggers of intrusive memories were Perceptual Cues, Thoughts/Emotions, Location/Environment/Situation and People. Participants could not identify a trigger in 13% (TBA) and 14% (EBA) of their events, respectively. Predictors of the frequency of intrusive memories were depressive symptomatology (BDI-II Total Score), BPD symptomatology (BSL-23 Mean Score) and negative cognitions (PTCI Total Score) with respect to EBA. The PTCI Subscore Negative Appraisals of Initial Posttraumatic Symptoms was predictive of frequency of intrusive memories in TBA.

The results suggest a higher frequency of intrusive memories than previously assumed, irrespective of the method. This implies that commonly used diagnostic interviews might be prone to ceiling effects and thus underestimate PTSD symptomatology. Moreover, significant differences were found for EBA and TBA concerning the different questions. These differences should be addressed in future research. Since we explicitly focused on a post-hoc analysis of the predictive factors, future research is recommended in order to investigate the significant predictors.