Re: differential mechanism/ SUDS/ eye movements

Hi Shawn. I should start by clearing up an apparent misconception in your response. You seem to assume that I hold strong opinions; I would characterize myself instead as having multiple questions and being exceptionally curious. I am also hopeful that dialogue and research will help us to develop new and better treatments, and to improve existing therapies. I’ve had excellent results treating PTSD with exposure, relaxation, and EMDR, and am a co-investigator in the Taylor study.

You wrote: “Here is where we agree: The pattern you describe does suggest the possibility of some mechanism operating in standard (i.e., eye movement) EMDR that is responsible for within session fear reduction that is not present in a no-eye movement variation of EMDR (e.g., Boudewyns et al., 1993) or in standard exposure therapy (Rogers et al., 1999).” And I agree that we agree.

You wrote: “Now where we may be in disagreement is whether or not treatment outcome is mediated through the same mechanism as standard exposure therapy, this new mechanism responsible for within-session fear reduction, or some other mechanism.” I don’t think we disagree here. Although, my guess is that this “new mechanism” might be a moderator, and not a mediator. And of course, this possibility needs to be evaluated by research investigating the relationship between fear reduction in session brought about by eye movements and treatment outcome. I also wonder if this mechanism might be more helpful to some client-types than others.

For example, you also wrote: “Is there any THEORETICAL reason to think that a dual task would enhance memory processing rather than detract from it? As I noted earlier, if symptoms persist because the memory has not been adequately processed, and processing requires cognitive resources, how is it that dividing these cognitive resources between two tasks leads to better processing?” This is an interesting question. Research by DePrince and Freyd (1999, ref below) found that a dual task enhanced cognitive processing for persons with higher DES scores on one element of the Stroop test for trauma related material. Preliminary research presented by Garvey at the EMDRIA 2001 conference found an advantage in a word retrieval task for persons with high DES who experienced saccadic EMs prior to retrieval. Obviously more research is needed to determine, for whom, if, how, when, and what dual tasks might be advantageous in processing traumatic memories.

You wrote: “I suggest that the parsimonious answer is that treatment outcome is mediated by the same mechanisms acting in exposure therapy.” I think that some of the resistance to, and confusion about this conclusion stems from understanding of exposure protocols, and clinical observations of the free association element in EMDR. Clients will often spend little time focused on the traumatic incident; instead they may move through a range of related material from various life experiences. No attempt is made to keep the focus on the original target. Now, one could say that this related material is part of the memory network, and that the client is being “exposed” to the traumatic material. However this is a broader interpretation of exposure than is commonly taken. Original theorists (e.g., Keane) suggested that such diversions were a form of avoidance. Perhaps the construct of exposure is expanding to include such apparently peripheral content? If so, it would appear that exposure therapy is evolving. I think such modification can be advantageous, but that it should be acknowledged.

I’ll respond re the van den Hout and Kavanaugh studies in my next post. Meanwhile here are the references:

DePrince, A., & Freyd, J. J. (1999). Dissociative tendencies, attention, and memory. Psychological Science, 10, 449-452.

Kavanaugh, D. J., Freese, S., Andrade, J., & May, J. (2001). Effects of visuospatial tasks on desensitization to emotive memories. British Journal of Clinical Psychology, 40, 267-280.

van den Hout, M., Muris, P., Salemink, E., & Kindt, M. (2001). Autobiographical memories become less vivid and emotional after eye movements. British Journal of Clinical Psychology, 40, 121-130.

Replies:

Re: differential mechanism/ SUDS/ eye movements, by Louise Maxfield, 11/11/01 Re: differential mechanism/ SUDS/ eye movements, by Cahill, 12/16/01

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