What has research determined about EMDR's eye movement component?
In 1989, Francine Shapiro (1995) noticed that the emotional distress accompanying disturbing thoughts disappeared as her eyes moved spontaneously and rapidly. She began experimenting with this effect and determined that when others moved their eyes, their distressing emotions also dissipated. She conducted a case study (1989b) and controlled study (1989a), and her hypothesis that eye movements (EMs) were related to desensitization of traumatic memories was supported. The role of eye movement had been previously documented in connection to cognitive processing mechanisms. A series of systematic experiments (Antrobus, 1973; Antrobus, Antrobus, & Singer, 1964) revealed that spontaneous EMs were associated with unpleasant emotions and cognitive changes.
There have been more than two dozen published randomized studies that investigated the role of EMs in EMDR. Studies have typically compared EMDR-with-EMs to a control condition in which the EM component was modified (e.g., EMDR-with-eyes-focused-and-unmoving). There have been four different types of studies: (1) case studies, (2) dismantling studies using clinical participants (3) dismantling studies using nonclinical analogue participants, and (4) component action studies in which eye movements are examined in isolation.
A recent meta-analysis has demonstrated the positive effects of the eye movement component.
Lee, C.W. & Cuijpers, P. (2013). A meta-analysis of the contribution of eye movements in processing emotional memories. Journal of Behavior Therapy & Experimental Psychiatry, 44, 231-239.
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).
A consistent significant effect for EMs in isolation in the 26 studies evaluated was found in reducing the vividness of, and affect associated with, autobiographical memories
An additional set of studies have demonstrated a number of other memory effects including the elicitation of episodic memory and the increased recognition of true information.
For an annotated list of studies see Research Overview.