How Does EMDR Really Work? What the New Science Is Beginning to Tell Us

If you've ever had EMDR, you've probably wondered...

"How on earth can moving my eyes backwards and forwards possibly help me recover from trauma?"

It's a fair question.

In fact, if someone had explained EMDR to me before I'd trained in it, I suspect I'd have smiled politely and thought...

"Well...that sounds a bit odd."

Years later, after seeing hundreds of clients transform in ways I genuinely couldn't explain through talking therapy alone, I'm less interested in whether EMDR works (we know it does), and far more fascinated by why it works.

The truth is...

Scientists still don't have one single answer.

Instead, the evidence suggests EMDR probably works through several mechanisms happening at the same time.

Rather like making the perfect cup of tea.

It's not just the tea bag.

It's the water.

The temperature.

The brewing time.

(And let's be honest...whether someone forgot to put the kettle on.)

EMDR seems to be much the same.

We used to think trauma was simply a memory.

Now we think it's much more than that.

Modern neuroscience suggests traumatic memories are stored differently from ordinary memories.

Rather than becoming neatly organised into the story of our lives, they can remain stored with their original emotions, body sensations, images and beliefs.

It's as though part of the brain never received the memo that the event finished.

So years later...

A smell.

A sound.

A facial expression.

A hospital corridor.

Someone raising their voice.

...and suddenly the nervous system reacts as though the danger is happening all over again.

Not because you're weak.

Because your brain is doing exactly what it evolved to do.

EMDR doesn't erase memories

This is one of the biggest myths.

People sometimes worry they'll forget what happened.

They won't.

The facts usually remain.

What changes is the emotional charge attached to them.

It's the difference between remembering being bitten by a dog...

...and feeling as though you're being bitten every time one walks past.

The working memory theory

One of the strongest explanations comes from something called working memory.

Our brains only have a limited amount of mental "bandwidth."

If you're recalling a distressing memory while simultaneously following bilateral stimulation (eye movements, tapping or tones), both tasks compete for that limited capacity.

It's a little like trying to watch two television programmes on one screen.

Neither can receive your brain's full attention.

The result?

The traumatic image often becomes less vivid.

Less emotionally intense.

And easier for the brain to process.

This theory has good experimental support and probably explains part of what happens during EMDR.

But that's probably not the whole story

If working memory explained everything...

EMDR sessions would feel fairly mechanical.

Instead, something much richer often happens.

People suddenly remember forgotten information.

They make completely unexpected connections.

Long-held beliefs shift.

Body sensations change.

Some even laugh halfway through processing because something that had felt enormous suddenly seems...well...rather ridiculous.

Not because it never mattered.

Because the brain has updated what it means.

The brain begins talking to itself again

Brain imaging studies suggest EMDR changes communication between several important brain networks.

The Amygdala-our alarm system-often becomes less reactive.

The Prefrontal Cortex-the part involved in reasoning, perspective and decision-making-becomes more engaged.

The Hippocampus, which helps place memories in time, also appears to become better integrated.

In simple terms...

Instead of the emotional brain shouting over everyone else...

The thinking brain finally gets a chance to join the conversation.

The nervous system matters too

One thing I particularly love about EMDR is that it doesn't only work with thoughts.

It works with the body.

Clients often notice:

"I can breathe."

"My shoulders have dropped."

"My chest feels lighter."

"My stomach has settled."

Those aren't side effects.

They're signs that the autonomic nervous system is changing.

We're moving away from survival and towards regulation.

Trauma isn't just psychological.

It's physiological.

And recovery often is too.

Memory reconsolidation may be the missing piece

One of the most exciting developments is the growing understanding of memory reconsolidation.

Every time an emotional memory is genuinely reactivated, it briefly becomes changeable before being stored again.

If, during that window, the brain experiences something new-perhaps safety instead of danger, choice instead of helplessness, compassion instead of shame-the emotional learning may be updated.

Not erased.

Updated.

Many researchers now believe this may be one of the key ingredients behind lasting therapeutic change.

Bilateral stimulation may help the brain integrate information

Exactly why bilateral stimulation helps remains debated.

Several ideas have been proposed.

It may:

• Reduce emotional intensity through working memory.

• Increase communication between brain networks.

• Promote orienting responses, allowing the nervous system to recognise that the danger has passed.

• Mimic some aspects of REM sleep, when emotional memories are naturally processed.

• Help integrate thoughts, emotions and body sensations into one coherent experience.

The reality is...

It may do all of these.

Biology rarely has one single explanation.

Why EMDR sometimes feels surprisingly fast

People often say,

"I don't understand how thirty years of trauma changed in one session."

It didn't.

The trauma took thirty years to accumulate.

But once the brain finally accesses the right memory network, change can happen remarkably quickly.

Think of it less like dismantling a brick wall one brick at a time...

...and more like discovering someone accidentally built the wall across the wrong doorway.

Once you move it, everything behind it becomes accessible again.

So...does anyone actually know how EMDR works?

Yes.

And no.

We know it works.

We know it changes the brain.

We know it changes the nervous system.

We know it changes the way memories are experienced.

Exactly which mechanism is doing the heavy lifting?

Probably all of them.

The more neuroscience develops, the more EMDR makes sense—not less.

Ironically, one of the therapies that once seemed the strangest has become one of the best supported by modern neuroscience.

And I suspect we're only just beginning to understand what is really happening inside the brain.

EMDR has evolved since Francine Shapiro first developed it. You could explain that we're no longer just talking about "adaptive information processing"; we now have insights from network neuroscience, predictive processing, interoception, autonomic regulation, and memory reconsolidation. EMDR hasn't stood still-it has been continually illuminated by advances in neuroscience.

References

Baek, J. et al. (2019). Neural circuits underlying a single session of eye movement desensitization and reprocessing. Nature, 566, 339-343.

Carletto, S., Oliva, F., Barnato, M., et al. (2021). Eye Movement Desensitization and Reprocessing (EMDR): A systematic review of neurobiological mechanisms. Frontiers in Psychology.

Lee, C. W., & Cuijpers, P. (2013). A meta-analysis of the contribution of eye movements in processing emotional memories. Journal of Behavior Therapy and Experimental Psychiatry, 44, 231–239.

Nader, K., Schafe, G. E., & LeDoux, J. E. (2000). Fear memories require protein synthesis in the amygdala for reconsolidation after retrieval. Nature, 406, 722–726.

Pagani, M., et al. (2017). Neurobiological responses to EMDR therapy in PTSD: A review. European Journal of Psychotraumatology.

Shapiro, F. (2018). Eye Movement Desensitization and Reprocessing (EMDR) Therapy: Basic Principles, Protocols and Procedures (3rd ed.). Guilford Press.

Stickgold, R. (2002). EMDR: A putative neurobiological mechanism of action. Journal of Clinical Psychology, 58, 61–75.