EMDR as treatment for post-traumatic stress disorder

Journal reference: Bisson JI, Roberts NP, Andrew M, Cooper R, Lewis C. Psychological therapies for chronic post-traumatic stress disorder (PTSD) in adults. Cochrane database of systematic reviews 2013 Dec 13(12):CD003388

Link: https://dx.doi.org/10.1002/14651858.CD003388.pub4

Published: December 2013

Evidence cookie says…

Eye movement desensitisation and reprocessing (EMDR) appears to be effective for post-traumatic stress disorder (PTSD) symptoms. the quality of the evidence is low the uncertainty to the effect-size estimate precludes a confident comparison of effectiveness with other therapies (such as trauma-focussed CBT) choice of initial therapy may depend on patient preferences, and local access and availability

This article was published in the March 2019 issue of Medical Observer under the title “Eyeing the past to end trauma”, and online under the title “Eye movement desensitisation and reprocessing for PTSD”.

Clinical scenario

Brian, a 49-year-old landscaper, lives with chronic post-traumatic stress disorder (PTSD). He was recently diagnosed after presenting in distress, revealing a history of a very traumatic past.  I remembered discussions on a GP online forum about eye movement desensitisation and reprocessing (EMDR) and wondered about the evidence for its efficacy, and how it compared to alternative psychotherapeutic approaches.

Clinical question

Is EMDR an effective treatment for PTSD, and how does it compare to trauma-focussed cognitive behavioural therapy (TF-CBT)?

What does the research evidence say?

Step 1: The Cochrane Library

The Cochrane Library has a relevant systematic review published in 2013 on psychological therapies for chronic PTSD in adults [1].  As this was systematic review was almost six years old, I undertook a search for updated reviews.

Step 2: TripDatabase and PubMed

I conducted a search using the TripDatabase PICO search tool (Participant: “PTSD”, Intervention: “EMDR”, Comparator: blank, Outcomes: blank).  This identified a couple of important systematic reviews in progress in the PROSPERO register [2,3].  Next, I conducted a PubMed search using the search term “EMDR and PTSD” limited to systematic reviews and publications since 2013.  This identified a systematic review by Khan et al. (2018) comparing EMDR to CBT for PTSD [4].  However, as this was published in Cureus, an unconventional journal using rapid crowdsourced peer review and post-publication review, I will preference the Cochrane systematic review by Bisson and colleagues [1].

Critical appraisal

I will use the systematic reviews critical appraisal sheet from the Centre for Evidence Based Medicine [5].

What PICO question does the systematic review ask?

In adults (18 year or older) living with chronic PTSD (as diagnosed by DSM-III, DSM-IV, ICD-9, or ICD-10) (Participants); what is the effect of a range of psychological therapies (including EMDR and TF-CBT) (Intervention); compared to waitlist/treatment as usual, or an alternative psychological treatment (Comparator); on reduction of severity of PTSD symptoms using a clinician-rated standardised measure (Outcome).

Is it clearly stated?

Yes.

Is it unlikely that important studies were missed?

Yes.  The search strategy was exhaustive and rigorously described.  The primary search was through specialised registers of studies maintained by the Cochrane Depression, Anxiety and Neurosis Group.  Multiple additional databases were searched, along with grey literature, and manual searching of guidelines and reference lists.

Were the criteria used to select articles for inclusion appropriate?

Yes.  The authors only included randomised trials (RCTs).

Were the included studies sufficiently valid for the question asked?

Unclear.  The authors formally accessed risk of bias of the included studies, and many studies were at unclear or high risk of bias for multiple domains.  Notably, funnel plots comparing TF-CBT vs waitlist/usual care (figures 4 and 6) suggest publication bias that overestimates the effect of therapy [1].  The studies included in the EMDR vs waitlist/usual care analysis were very small with only one with more than 50 participants.

Were the results similar between studies?

No.  There were substantial differences in effect size (I²=84%) between studies (EMDR vs waitlist/usual care), though all but one study favoured EMDR.

What were the results?

EMDR vs waitlist/usual treatment on clinician-rated PTSD symptoms, 6 studies (183 participants):

• Standardised mean difference (see Stat Facts): -1.17 (95% CI -2.04 to -0.30)
• note: large effect size favouring EMDR, though there is substantial imprecision in the effect size estimate

EMDR vs TF-CBT on clinician-rated PTSD symptoms, 7 studies (327 participants):

• SMD: -0.03 (95% CI -0.43 to 0.38)
• note: minimal difference, though substantial imprecision in the estimate of the effect size difference

Discussion and conclusion

It is unclear how EMDR works.  A range of models on the mechanism of action are hypothesised, including psychological, psychophysiological, and neurobiological, but no firm conclusions can be made from existing data [6].

This Cochrane systematic review demonstrates that EMDR appears to be effective for PTSD in adults, potentially with a large effect size compared to a waitlist/minimal care.  EMDR when compared with trauma-focussed CBT did not appear to be meaningfully different in this analysis.  These analyses seem to point towards EMDR and TF-CBT as more effective than “other therapies” (including supportive therapy, non-directive counselling, psychodynamic therapy).  In the context of the low quality of evidence, we need to be very cautious of making strong conclusions of superiority.  Most of the included studies were small, had problems with bias, with results that were statistically heterogeneous.  Interestingly, the “other therapies” were still superior to waitlist/usual care with a moderate effect size (SMD = -0.58, 95% CI -0.96 to -0.20).

A pragmatic interpretation of the evidence is that EMDR appears to work for PTSD symptoms, though it’s magnitude of effect is quite uncertain.  The decision on the choice of therapy may depend on patient preferences, and local access and availability.

Stat Facts

Standardised mean difference

The value of the SMD is literally the difference in effect size between groups expressed as a proportion of the pooled standard deviation.  So, in this paper the average difference in PTSD symptoms in the EMDR group, compared to those in the waitlist/usual care group, was 1.17 standard deviations – a large effect.  Rule of thumb for effect sizes: small (SMD=0.2), moderate (SMD=0.5), large (SMD=0.8).

References

1. Bisson JI, Roberts NP, Andrew M, Cooper R, Lewis C. Psychological therapies for chronic post-traumatic stress disorder (PTSD) in adults. Cochrane database of systematic reviews 2013 Dec 13(12):CD003388.
2. Odette Megnin-Viggars, Steve Pilling. Trauma-focused therapies (trauma-focused CBT and EMDR) for adults with PTSD: a meta-analysis and meta-regression. PROSPERO 2018 CRD42018100169 Available from: http://www.crd.york.ac.uk/PROSPERO/display_record.php?ID=CRD42018100169
3. Rebekka Gehringer, Antje Freytag, Peter Schlattmann, Konrad Schmidt, Sven Schulz, Mathias Berger, Horst Christian Vollmar, Jochen Gensichen. Systematic review and meta-analysis of psychological interventions for posttraumatic stress disorder (PTSD) in primary care settings. PROSPERO 2017 CRD42017060123 Available from: http://www.crd.york.ac.uk/PROSPERO/display_record.php?ID=CRD42017060123
4. Khan AM, Dar S, Ahmed R, Bachu R, Adnan M, Kotapati VP. Cognitive Behavioral Therapy versus Eye Movement Desensitization and Reprocessing in Patients with Post-traumatic Stress Disorder: Systematic Review and Meta-analysis of Randomized Clinical Trials. Cureus 2018 Sep 4;10(9):e3250.
5. Centre for Evidence Based Medicine. Systematic Review: Are the results of the review valid? Oxford: University of Oxford, 2005.
6. Landin-Romero R, Moreno-Alcazar A, Pagani M, Amann BL. How Does Eye Movement Desensitization and Reprocessing Therapy Work? A Systematic Review on Suggested Mechanisms of Action. Front Psychol 2018;9:1395.