Can working memory account for EMDR efficacy in PTSD?

BACKGROUND: Although eye movement desensitization and reprocessing (EMDR) has been shown to be effective in the treatment of PTSD for years, it remains controversial due to the lack of understanding of its mechanisms of action. We examined whether the working memory (WM) hypothesis –the competition for limited WM resources induced by the dual task attenuates the vividness and emotionality of the traumatic memory – would provide an explanation for the beneficial effect induced by bilateral stimulation. METHODS: We followed the Prisma guidelines and identified 11 articles categorized in two types of designs: studies involving participants with current PTSD symptoms and participants without PTSD diagnosis. RESULTS: Regardless of the types of studies, the results showed a reduction of vividness and emotionality in the recall of traumatic stimuli under a dual-task condition compared to a control condition, such as recall alone. However, two studies used a follow-up test to show that this effect does not seem to last long. CONCLUSION: Our results provide evidence for the WM hypothesis and suggest that recalling a traumatic memory while performing a secondary task would shift the individual’s attention away from the retrieval process and result in a reduction in vividness and emotionality, also associated with the reduction of symptoms.