Role of EM and stimulus valence presentation order in the return of fear: Possible implications for the therapeutic mechanism

Research background & aims: This study examined possible therapeutic mechanisms of eye movements in Eye Movement Desensitization and Reprocessing (EMDR; Shapiro, 1989, 1995, 2001) in terms of exposure and information processing model. While exposure model contended process of extinction and response habituation, Stickgold (2002) proposed that sleep induced change in associative memory via activation of weak association during REM state and EM functioned as REM sleep to integrate the episodic memory of trauma into general semantic memory. In this study, the effect of EM compared to that of Exposure-Only (non-EM) on process measures of SUDs, ratings of cockroach phobia across sessions, along with outcome measures were examined. Specifically, the degree of return of fear and response habituation was explored. Methods: Thirty-six college students with cockroach phobias were recruited as participants and invited after informed consent for 4 1-week interval treatment sessions and a 1 month follow-up session. The instruments for outcome measures included Cockroach Phobia Questionnaire, fear ratings of cockroach slides, FSS, STAI-S, BDI, short form of SCL-90, the Revised Thought-Action Fusion Questionnaire, White Bear Suppression Inventory, and cognitive tasks for measuring strength of associations. The SUDs, credibility and therapeutic relationship rating, and physiological measures such as HR, HRV, EOG, served as process measures. Due to space limitations, the results of cognitive task and physiological measures were reported elsewhere. The participants were randomly assigned to one of the four groups: EM condition (EM vs. Non-EM exposure only) × block order of cockroach theme presentation (negative cognition first vs. positive cognition first). A 2 (EM condition) × 2 (order of valence presentation) × 9 (time: pre-assessment and post-assessment for each of the 4 sessions plus 1 month follow-up assessment) mixed factorial design was performed, with time serving as within Ss factor and the other two variables serving as between Ss factors. There were 20 trials in each therapeutic session. The duration of each trial was 30s for both the EM and Exposure-Only conditions. Results: After preliminary analyses for group differences on pretreatment variables, credibility-relationship ratings, and outcome variables were explored, the 2 (EM condition) × 2 (order of valence presentation) × 9 (time) ANOVA on SUDs showed that the main effects of time and EM were both significant (p < .001 and p < .034). Subsequently, two 2 (order of valence presentation) × 9 (time) ANOVAs were performed for EM condition and Exposure-Only condition, respectively. The results showed that for EM condition, only time effect was significant (p < .006); while for Exposure-Only condition, there were a significant time effect (p < .001) and an approaching significant valence presentation order effect (p< .065), with the SUDs being higher in negative cognition presented first condition compared to positive cognition presented first condition; whereas the effect was not significant for the EM condition. Using trend analyses and inspection of time effect showed that significant within session SUDs reduction for Exposure-Only conditions. Notwithstanding, the pairwise comparisons for the 9 time points indicated salient phenomena of return of fear among several of the 5 sessions for this condition when comparing the pre-assessment of each session with post-assessment of its previous session. Whereas for EM condition the return of fear between sessions was small and the trend analysis showed a reduction with linear trend. Conclusions & Discussion: Compared to Exposure-Only, EM resulted in less degree of sufferings while participants encountering negative theme which in turn might facilitate further processing of negative memory. In addition, EM might add something beyond the mechanism of pure exposure. The less return of fear indicating that information processing in addition to response inhibition might take place between sessions. The results echoed Shapiro’s Adaptive Information Processing model and Stickgold’s REM-sleep dependent memory reprocessing model, suggesting that EM in EMDR might reflect a shift in associative memory systems by activating different strength of associations of negative semantic nodes for different semantically related words. Given that previous research showed that EM decreased emotionality and also generate greater amount of associations for negative stimuli, the implications of the present results from theoretical and therapeutic point of views and future research possibilities are discussed.

Conference

English

Sue-Hwang Chang

Chang, S.-H. (2007, September). Role of EM and stimulus valence presentation order in the return of fear: Possible implications for the therapeutic mechanism. Presentation at the 12th EMDR International Association Conference, Dallas, TX