The Science Behind EMDR: What Research Says About How It Works
EMDR (Eye Movement Desensitisation and Reprocessing) is a structured psychological therapy developed by Dr Francine Shapiro in the late 1980s. It is now an established treatment for post-traumatic stress disorder (PTSD) and is recommended within UK clinical guidance.
What makes EMDR particularly interesting is that its clinical effectiveness for PTSD is better established than our understanding of precisely why it works.
This article explores how EMDR therapy works, what happens when traumatic memories are processed, and what current research tells us about possible mechanisms such as working memory and bilateral stimulation.
What Does EMDR Therapy Actually Involve?
EMDR is based on the idea that distressing experiences can sometimes continue to affect a person long after the original danger has passed.
A memory might trigger emotions, physical sensations or beliefs that feel immediate, even though the person consciously knows the event happened in the past.
During EMDR, the client brings aspects of a distressing memory to mind while engaging in bilateral stimulation. This most commonly involves following the therapist’s fingers from side to side with the eyes, although alternating taps or tones may also be used where appropriate.
EMDR is not simply a set of eye movements. It follows a structured therapeutic protocol involving history-taking, preparation, assessment, memory processing and review.
If you would like to see how this works in practice, read what an EMDR session looks like.
What Does the Evidence Say About EMDR?
EMDR has a substantial evidence base for the treatment of PTSD.
In the UK, NICE recommends EMDR for adults with PTSD or clinically important PTSD symptoms in appropriate circumstances. NICE specifies that treatment should use a validated manual, be delivered by appropriately trained practitioners and include repeated bilateral stimulation while particular traumatic memories are being processed.
This means that EMDR should not be presented simply as an alternative or experimental therapy for PTSD. It is one of the established trauma-focused psychological treatments available.
However, evidence for EMDR is not equally strong across every psychological difficulty for which it is sometimes promoted. PTSD remains the condition for which its clinical evidence is most firmly established.
How Does EMDR Work?
This is where the science becomes particularly interesting.
Researchers have proposed several explanations for EMDR’s effects, but there is still no single proven neurological mechanism that completely explains the therapy.
The Adaptive Information Processing Model
EMDR was developed around what is known as the Adaptive Information Processing (AIP) model.
Within this theoretical model, some distressing experiences may remain insufficiently processed, so aspects of the original memory continue to be activated by situations in the present.
The goal of EMDR is to help the person process the memory so that it can be remembered without producing the same level of distress.
The AIP model is an important part of EMDR theory, but it should not be mistaken for a complete neuroscientific explanation of how the treatment produces its effects.
The Working Memory Explanation
One of the better-supported explanations involves working memory.
Working memory has limited capacity. If someone recalls a vivid distressing image while simultaneously carrying out another demanding task, such as making repeated eye movements, both activities compete for those limited resources.
This may make the recalled image temporarily less vivid and less emotionally intense.
A systematic review examining the working-memory explanation found that recalling traumatic material while performing a secondary task was associated with reductions in the vividness and emotionality of the memories compared with recall alone.
Read the systematic review of the working-memory hypothesis on PubMed.
What About Memory Reconsolidation?
Memory is not necessarily a fixed recording that is retrieved unchanged each time we remember something.
When a memory is recalled, it can become temporarily open to modification before being stored again. This process is known as memory reconsolidation.
Researchers have explored whether processes of this kind may contribute to EMDR, alongside working-memory effects and changes in physiological arousal.
These remain active areas of research. It is more accurate to describe them as potential mechanisms than to say that scientists have definitively identified exactly how EMDR changes the brain.
Does EMDR Work by Activating Both Sides of the Brain?
You may have seen EMDR explained as a therapy that works because eye movements “activate both hemispheres of the brain”.
That explanation is appealing because EMDR uses bilateral stimulation, but it oversimplifies the research.
The brain does not operate as two largely independent halves that simply need to be switched on together. Current research into EMDR considers several possible mechanisms, including working-memory taxation, changes in arousal, memory reconsolidation and neural processes associated with eye movements.
A systematic review of proposed EMDR mechanisms found reasonable empirical support for the working-memory hypothesis, while also concluding that research into the mechanisms underlying EMDR remains at a relatively early stage.
Read the systematic review of proposed EMDR mechanisms on PubMed.
Does EMDR Mimic REM Sleep?
Another popular explanation compares EMDR eye movements with the rapid eye movements that occur during REM sleep.
There are interesting theoretical similarities, and researchers have investigated relationships between eye movements, memory and emotional processing.
However, it has not been established that EMDR simply recreates REM sleep while someone is awake.
Descriptions such as “waking REM” should therefore be treated as hypotheses or metaphors rather than settled explanations of how EMDR works.
Is Bilateral Stimulation Important?
Bilateral stimulation is a distinctive component of EMDR and normally involves eye movements, alternating taps or alternating sounds.
Research has investigated whether eye movements contribute something beyond simply recalling and discussing the traumatic memory.
Studies examining the working-memory hypothesis provide evidence that performing a competing task during memory recall can reduce the vividness and emotional intensity of distressing memories. However, researchers continue to investigate how this contributes to longer-term therapeutic outcomes.
This is another reason to be cautious about simplistic explanations. The evidence supports EMDR as a complete therapeutic treatment for PTSD more clearly than it supports any single explanation for why each individual component works.
What About Rhythm, Movement and the Nervous System?
Rhythm, movement, music and repetitive activities have played roles in human social, cultural and wellbeing practices for centuries.
People may also find activities such as walking, dancing, music or rhythmic movement calming or emotionally meaningful.
However, these activities should not be described as equivalent to EMDR simply because they involve alternating movements or rhythm.
EMDR is a specific psychological treatment involving clinical assessment, preparation, selected memory targets, bilateral stimulation and a structured therapeutic protocol.
Going for a walk may be beneficial for wellbeing, but it is not the same process as receiving EMDR therapy.
Who May Benefit from EMDR?
The strongest evidence for EMDR relates to PTSD and trauma-related symptoms.
People seeking EMDR may have experienced:
- single-event trauma such as an accident or assault
- repeated or childhood traumatic experiences
- medical trauma
- work-related traumatic experiences
- distressing memories that continue to trigger PTSD symptoms
EMDR has also been researched and used for other psychological difficulties, but the quality and quantity of evidence varies by condition.
It is therefore better to assess whether EMDR is appropriate for the individual than to assume it is an established treatment for every difficulty associated with distress or difficult memories.
If you want to explore the research in more detail, Philip has also written about the evidence for EMDR therapy.
Do You Have to Talk About Everything?
One feature that attracts some people to EMDR is that detailed verbal disclosure of every part of a traumatic experience is not normally required.
The therapist still needs enough information to understand the client’s difficulties, plan treatment and work safely, but much of the processing occurs while the client internally attends to their own memories, thoughts, emotions and sensations.
This can make EMDR particularly interesting to people who find detailed retelling of traumatic experiences difficult.
EMDR and the Brain: What We Know
There is good evidence that EMDR can reduce PTSD symptoms.
There is also growing evidence that working-memory processes may contribute to the effects produced by eye movements and other dual-attention tasks.
What we do not yet have is a simple neurological explanation showing that EMDR works because it activates particular hemispheres, reproduces REM sleep or switches specific brain pathways on and off.
That distinction matters.
A therapy can have evidence showing that it works even while researchers continue to investigate exactly how it produces those effects.
Final Thoughts
EMDR is an evidence-based psychological treatment with particularly strong support for PTSD. It combines attention to traumatic memories with bilateral stimulation within a structured therapeutic process.
The science behind EMDR continues to develop. Working-memory research offers one plausible explanation for some of its effects, while other theories examine memory reconsolidation, arousal and neurobiological processes.
For someone experiencing the ongoing effects of trauma, the important question is not whether EMDR can be reduced to one simple explanation about the brain. It is whether an appropriately assessed, evidence-based trauma treatment is suitable for their individual needs.
If you are considering treatment, you can learn more about EMDR therapy with Philip Bruce or contact Philip to discuss whether EMDR may be appropriate for you.
