Comment on Point #2

You raise an important measurement issue, whether a floor effect precluded the possibility of improvement. There are a few things to consider here.

First, SUDs were significantly lower and VoC significantly higher after treatment in the no eye movement condition than in the non-directive therapy condition, and similar trends were observed for the EMD condition.

Second, there was a significant effect of time for the IES, indicating significant reductions on the IES occurred over assessments that did not differ across groups.

Third, I computed within group effect sizes as another way to gauge the magnitude of the treatment effect (I used the formula that was used in the van Etten & Taylor meta-analysis). The resulting effect sizes on the IES total score for EMD, EMD minus eye movements, and non-directive therapy were .86, 1.37, and .95 respectively.

Thus, there clearly was room for improvement. Moreover, the dissociation between process markers and outcome is of interest, as it has been seen in other studies (e.g., Boudewyns et al., 1993; all of the group EMDR studies on phobias). This is one of the reasons many people were skeptical of Shapiro (1989), whose only measures to compare EMD with the control condition were SUDs and VoC. None of these findings provide any support for the strong hypotheses outlined in Shapiro (1989; see my previous post for documentation of this).

Van Etten, M. L., & Taylor, S. (1998). Comparative efficacy of treatments for post-traumatic stress disorder: A meta-analysis. Clinical Psychology and Psychotherapy, 5, 126-144.

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