The Power Study - Not Just the Abstract

A colleague from yet another continent has sent me a copy of the Power Study; because of the round of flu going around, I have had three patients cancel today, and am using the time to review and comment on these two articles (this and Lytle et al).

This study is an important contribution because it is much sounder methodologically than most of its predecessors. It has a lot more power, because there are 72 patients in the sample at end of treatment. It has an appropriate level of EMDR dosage - as many as 10 sessions were used for each treatment condition, though they stopped treatment earlier when both client and therapist agreed upon it. Another strength is that the therapists were trained by the EMDR Institute at Levels I and II, both. There was a check for treatment fidelity using audiotapes.

It compares EMDR to its closest "rival", namely, exposure (in vitro) plus cognitive restructuring, and a waiting list control. This is good.

One thing is not clear to me upon reviewing the methodology for selection and measurement. Namely, was the treatment targeting subjects with a single trauma causing their PTSD, or did it consider both singly-traumatized patients with PTSD diagnosis as well as those with a complex trauma history, with PTSD. The IES addresses reactions to a given event; PTSD scales usuaully are assessing against the diagnosis of PTSD. Selection was for people with PTSD (and excluded those with severe depressive illness, psychotic illness, alcoholism/drug abuse in last six months, suicidal ideation /intent, significant physical illness, other psychotherapy commitments. There is no discussion that I could see of multiple traumas, so we don't know if the groups are matched for that confounding factor. Random assignment theoretically helps with that, but it's relevant and should be considered in the design/controls so we know what's being treated. Simple example: A client with PTSD after a rape and no prior trauma is not the same as a client with PTSD after a car accident with a childhood history of sexual and/or physical abuse with its own PTSD sequelae.

There was a differential drop out rate for the two treatment conditions, with more dropping out of Exposure than of EMDR (43% compared to 31%). This difference washes out when broken down by who dropped out before and after treatment commences, but by then again the sample sizes are small in those subsets, so power is lost - this may be responsible for the absence of significance in the difference in drop out rates. Both treatments had higher drop out rates than the waiting list control. It is gratifying to know that dropping out correlated with a higher score on the avoidance subscale of the CAPS.
Treatment effects over all were consistent with not much difference between the two treatment conditions across a considerable number of measures, EMDR did as well as exposure & cognitive restructuring. (Actually, EMDR did better than Wait List across all measures, whereas Exposure did better across only some measures).
This absence of much difference may be because EMDR is merely another exposure method. Or it may be that the fact that the Exposure and Cog Restructuring condition had an additional one hour of homework assignment of listening to their exposure tapes for 10 weeks, (that's up-to-70 of hours of exposure time in addition to up-to-10 sessions), if I understand the design. The average number of EMDR treatment sessions was 4.2 (SD 2.5) in comparison to 6.4 (SD 3.2) for the Exposure/Cog Restructing condition, but one really should say 6.4 plus one hour a day of homework listening to the exposure tape. If subjects did even half of their homework assignments, that would mean EMDR treatment at 4.2 sessions, and Exposure at 6.4 plus 20+ hours of homework. If they did it all it would be 45 hours of homework)

At follow up, there was no different in the proportion of patients maintaining clinically significant change for PTSD, anxiety and social functioning, and the initial clinically significant advantage EMDR had over E&CR disappeared at follow up. The only significant difference was on the disability measure, where 73% of EMDR versus 35% of the E&CR group had improved clinically significant scores.

The majority of patients in both treatment conditionsdid not maintain their gains without additional treatment. Again, I wonder whether patients were actually carrying a complex trauma history and were treated for one or some and not all of their traumas, yet measured for PTSD conditions in general. Again, there must be sufficient dosage to treat sufficient traumatic memories to achieve resolution of PTSD, so not knowing how many traumas subjects carried is a drawback to understanding the results.

The authors wonder why EMDR would be better than E&CR at reducing depression, as this study found. It may be due to the large number of analyses conducted (due to the large number of measures) which increases the likelihood that significant differences may appear randomly. It may also be due to a real difference, not a statistical artifact. We don't know.

A caution comes to mind about the fact that both treatment conditions had patients on concurrent psychotropic medication and at follow up both conditions hadn't maintained their gains. EMDR practice clearly cautions that EMDR conducted on psychotropic medicaitons may need to be revisited after the patient is no longer on the medication to get complete resolution.

In general, this study improves on many of the failings of prior research. Future studies should address the issue of single versus complex trauma histories head on in its design including screening for dissociative conditions that may confound the results.

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