How does EMDR work?
Not enough is yet known about the brain's response to psychological trauma or about EMDR to be certain how EMDR works. Indeed very little is known about the specifics of how any of the research-supported forms of psychotherapy work.

Current theory suggests EMDR's known effects may result from an interaction of several factors including imaginal exposure, cognitive restructuring and self-regulation methods properly integrated with the structured use of alternating sensory stimulation. However there is evidence that EMDR's known treatment effects cannot be adequately explained by any of the psychological theories which contributed some elements to EMDR procedures (such as Systematic Desensitization, Exposure-Flooding, Cognitive Behavioral theory).

The Adaptive Information Processing model developed by Dr. Shapiro proposes that EMDR stimulates an intrinsic human capacity for adapting to and learning from new and stressful life experiences which normally operates during the rapid eye movement (dreaming) phase of sleep. Research shows consolidation of emotional learning takes place during REM, also known as paradoxical sleep. Some theorists propose that EMDR may catalyze this innate capacity to resolve disturbance by focusing on a traumatic memory while deliberately engaging eye movements and may tap into some of the same neurological processes active in REM sleep.

Another leading theory proposes that some of the distinctive benefits of psychotherapy with EMDR result from the neurological effects of dual attention to the memory and to current (alternating) sensory stimuli. These theorists propose that attending to certain types of sensory stimuli at the same time as a memory triggers "an investigatory response" which leads to changes in the way memories are held in the brain.