Re:Lytle Study - Not Just the Abstract

There's another issue here that has been touched on but not fully addressed. Although many people seem to believe that EMDR is merely Exposure plus Eye Movements, in fact it is a systematic approach that incorporates a number of effective trauma treatment components in a somewhat unique package (e.g. see Hyer, L. & Brandsma, J. M. (1997). EMDR minus eye movements equals good psychotherapy. Journal of Traumatic Stress, 10, 515-522. Also Sweet, A. (1995). A theoretical perspective on the clinical use of EMDR. The Behavior Therapist, 18, 5-6.)

So supposing that eye movements don't really make a difference, but that EMDR is still somehow different than Exposure anyway? Or supposing that eye movements do make a small difference, that combined with the EMDR package, altogether the total effect is substantial? In either of these cases, a dismantling study such as Lytle's will not find much. Even if the effect of EMDR is large compared to a wait-list control (such as in Shapiro's 1989 study), comparing essentially similar forms of EMDR will be unlikely to find any difference. Remember Pitman's similar design, he found no difference between treatment and control, although Lipke did his own analysis and did find one predictor of outcome (across groups): treatment fidelity.

There is also the dosage problem that Sandra mentions, I think that's also a problem with the original Shapiro study, nowadays we think single-session studies are inappropriate. I am not blaming the researchers (given when the study was conducted), but it does make the findings hard to interpret.

Even with appropriate dosage and proper treatment according to current standards, all we could learn from the findings - assuming it came out the same - is that EMDR with fixed eyes is not very different from EMDR with moving eyes. That either it is not at all different, or that the effect is too small to be detected in a low-power study. So what would that mean? That fixed-eyes is a lot like eye movements? That fixed-eyes is not like eye movements? That eye movements may contribute only a small effect? Or none?

That's why dismantling studies should use much larger N's - because any given component of a treatment is not very likely to have a large effect.

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Re:Lytle Study - Not Just the Abstract, by Cahill, 10/25/02

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