EMDR Therapy: What the Science Now Tells Us About Healing Trauma

A deeper look at why EMDR works, who it helps, and what makes it different to every other therapy you may have tried.

By Jemma Dennis | Psychotherapist & EMDR Therapist | Wimpole Street, London | April 2026

There is a particular kind of frustration that many of my clients describe before they come to see me. They have done the work. Years of it, sometimes. For the most part they understand their patterns. They can trace the threads of their anxiety, their hypervigilance, their difficulty trusting, all the way back to their origins. They are articulate, self-aware, and committed.

And yet something in them still has not shifted.

The feeling remains. The body still braces. The memory still feels close. The past, despite everything, still feels present.

This is one of the most important things to understand about trauma: insight alone does not always heal it. Knowing why you feel the way you do is powerful but EMDR addresses something different with it as it works where the memory itself is stored.

Why trauma gets stuck

To understand why EMDR works, it helps to understand what happens in the brain when we experience something overwhelming.

Under normal circumstances, the brain processes experiences in a way that allows them to be stored as memories: filed away, integrated, given context. The memory of a stressful event can be recalled without triggering the same physiological response you had at the time.

But when something is experienced as genuinely overwhelming, the brain's processing system can become disrupted. The memory does not get filed away in the usual manner. Instead, it can be stored in a fragmented, incomplete state, still carrying the original emotional and physical intensity.

This is why trauma memories often feel not like recollections, but like intrusions. They arrive unbidden, sharp, physical. The body responds as if the event is happening now, not because the person is weak or irrational, but because, neurologically speaking, the memory was never fully processed.

What EMDR actually does

EMDR stands for Eye Movement Desensitisation and Reprocessing. It was developed in the late 1980s by Francine Shapiro, following a discovery that deliberate eye movements appeared to reduce the disturbance associated with difficult thoughts.

In the decades since, EMDR has been studied extensively. It is now recommended by the National Health Service (NHS), the World Health Organisation (WHO), and the National Institute for Health and Care Excellence (NICE) as a first-line treatment for PTSD.

But what is it actually doing? During EMDR processing, the client focuses on a disturbing memory while simultaneously engaging in bilateral stimulation: typically following a therapist's finger movements with their eyes, or using knee tapping. This dual attention, holding the memory while doing something else simultaneously, appears to allow the brain's natural processing system to resume.

The working theory is that bilateral stimulation mimics the rapid eye movements that occur during REM sleep, a phase of sleep during which the brain naturally processes and consolidates memories. By recreating this state while the client is awake and the memory is active, the brain can do what it was unable to do at the time of the original experience.

The result is not that it's going to erase the memory, but to change it in it's quality and experience. What was raw and reactive becomes something that happened, rather than something that is still happening.

EMDR and the nervous system

One of the things that makes EMDR distinct from purely cognitive approaches is that it works directly with the body.

Trauma is not only held in thought. It is held in the nervous system: in patterns of hyper-arousal, freeze, or shutdown that can persist long after the original experience. Many clients come to me describing symptoms that feel physical: a tightness in the chest, an inability to relax, a tendency to startle easily, a background hum of anxiety that does not seem to respond to rational reassurance.

EMDR processing often produces a physiological shift. Clients describe a loosening, a settling, a sense that something they have been bracing against has released. This is the nervous system updating: moving from a state organised around threat to one that recognises safety.

Not just for 'big T' trauma

One of the most important developments in the understanding of trauma over the past decade is the recognition that it does not need to involve a single, dramatic event to leave a lasting mark.

What we now call 'complex' or 'developmental' trauma refers to the cumulative effect of repeated difficult experiences, often in childhood: emotional neglect, inconsistent caregiving, growing up in an environment of chronic stress, having needs that were repeatedly unmet or dismissed.

These experiences may not look dramatic from the outside. They may not fit the template of what we traditionally call trauma. But their impact on the developing nervous system, on attachment patterns, on self-worth, and on the way the body holds stress, can be profound and lasting.

EMDR is effective for:

Post-traumatic stress disorder (PTSD) and complex PTSD

Anxiety and panic

Phobias

Depression rooted in past experiences

Low self-esteem and negative core beliefs

The effects of childhood emotional neglect or difficult family dynamics

Relationship patterns that feel compulsive or hard to shift

How EMDR differs from talking therapy

This is perhaps the question I am asked most often by clients who have previous experience of psychotherapy.

Talking therapy invites reflection, narrative, and understanding. At its best, it is extraordinarily powerful, and I integrate it into my work with every client. But it operates largely through the medium of language and conscious thought.

EMDR operates at a different level as it works by helping the brain's own processing system complete something it was unable to finish.

This is why clients who have done extensive talking therapy and still feel stuck often find EMDR reaches something that previous work has not. The two approaches are complementary, not competing. I use them together within the same therapeutic relationship.

What to expect in sessions

EMDR is conducted in structured phases, and a good EMDR therapist will never rush this process.

The early phases involve careful history-taking and goal-setting. I want to understand what we are working toward, and to build a thorough picture of your history before we approach anything difficult.

Before any processing begins, we spend time developing what is called resourcing: grounding techniques and inner resources that you can use if the processing becomes too intense. You will never be thrown into the deep end.

The processing itself involves holding a specific memory, or aspect of a memory, in mind while engaging in bilateral stimulation. I guide this carefully, and you are in control of the pace throughout.

After each processing session, we check in thoroughly with how the memory feels now, and what has shifted. Sometimes the change is gradual. Sometimes it is striking even within a single session.

If you would like to explore whether EMDR is right for you, I offer initial consultations from my practice on Wimpole Street, London or online. I would be glad to hear from you. Visit www.jemmadennis.com to get in touch.