A meta-analysis of the contribution of eye movements in processing emotional memories

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Abstract

Background and objectives

Eye Movement Desensitisation and Reprocessing (EMDR) is now considered evidence based practice in the treatment of trauma symptoms. Yet in a previous meta-analysis, no significant effect was found for the eye movement component. However methodological issues with this study may have resulted in a type II error. The aim of this meta-analysis was to examine current published studies to test whether eye movements significantly affect the processing of distressing memories.

Method

A systematic review of the literature revealed two groups of studies. The first group comprised 15 clinical trials and compared the effects of EMDR therapy with eye movements to those of EMDR without the eye movements. The second group comprised 11 laboratory trials that investigated the effects of eye movements while thinking of a distressing memory versus the same procedure without the eye movements in a non-therapy context. The total number of participants was 849.

Results

The effect size for the additive effect of eye movements in EMDR treatment studies was moderate and significant (Cohen's d = 0.41). For the second group of laboratory studies the effect size was large and significant (d = 0.74). The strongest effect size difference was for vividness measures in the non-therapy studies (d = 0.91). The data indicated that treatment fidelity acted as a moderator variable on the effect of eye movements in the therapy studies.

Conclusions

Results were discussed in terms of current theories that suggest the processes involved in EMDR are different from other exposure based therapies.

Highlights

► Previous meta-analysis that concluded eye movements are irrelevant had methodological issues. ► Eye movements effect processing emotional memories when compared to no eye movements. ► The effect size for eye movements in a therapy context was moderate and significant. ► The effect size for eye movements in a laboratory setting was large and significant. ► EMDR treatment fidelity was associated with a larger effect size for eye movements.

Section snippets

Search procedure

Searches were conducted in Medline, PsycINFO, and Science Direct databases. The search was done in two parts: the first used the keywords non eye movement or no eye movement or eyes fixed or eyes stationary or without the eye movement or eye stationary paired with eye movements, or eyes moving or eye movement; the second also used a keyword search of eye movements paired with eye movement desensitization. The search was restricted to articles only involving humans and between 1989 (when EMDR

Inclusion of studies

A flowchart describing the selection of studies is reported in Fig. 1. The three searches and four articles resulted in 891 unique studies. Of these 103 were excluded because they studied the effect of eye movement during sleep and 314 were excluded because they contained no original data and were review papers only. A further 297 were excluded because they were either a case report of EMDR treatment or a study looking at a treatment outcome study comparing EMDR to a waitlist or an alternative

Discussion

The present meta-analysis provided an up-to-date evaluation of the efficacy of eye movements in processing emotional memories. The 14 studies that investigated the additional value of eye movements in EMDR treatment averaged a significant medium effect size advantage for eye movements over no eye movement. Heterogeneity was found to be moderate in these analyses, and this was reduced to zero after removal of two possible outliers. In 10 laboratory studies that looked at the effects of eye

Acknowledgements

We received no financial support for the work reported in this paper.

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