When Pain Becomes Complex: How the Brain and Body Amplify Pain

Pain is one of the body’s most powerful protective systems — but sometimes, that protection can go into overdrive.

At The Flow Clinic, we often see people who are living with persistent pain long after their injury has healed. Their experience isn’t “all in the head” — it’s the result of real changes in how the nervous system, immune system, and brain interact.

This is what we call complex pain — and one of its most striking examples is Complex Regional Pain Syndrome (CRPS).

🩹 From Injury to Amplified Pain

CRPS often begins with an apparently minor injury — a sprain, a fracture, or surgery.In some people, that local injury triggers an exaggerated pain response.

Inflammatory chemicals (like IL-1β, IL-6, TNF-α, substance P, and CGRP) flood the area to promote healing. But in CRPS and other chronic pain syndromes, this response doesn’t switch off. The result is hypersensitivity, swelling, and pain that feels disproportionate to what’s happening in the tissues.

Even after the injury heals, pain persists — because the nervous system keeps “protecting” the area, long after the threat has passed.

⚡Central Sensitisation: When Protection Becomes Overprotection

The term central sensitisation describes what happens when the spinal cord and brain start amplifying normal sensory input into pain.

Think of it like the volume knob on your pain system being turned up too high.

This is common in conditions like fibromyalgia, CRPS, and phantom limb pain, where:

• Pain signals are amplified in the spinal cord.

• The brain’s “map” of the body becomes blurred (cortical smudging).

• The body feels painful, heavy, or foreign — even in the absence of ongoing damage.

• The autonomic (fight-or-flight) system stays switched on.

🔁 The Loop Between Body, Brain, and Emotion

Once central sensitisation develops, several systems start to reinforce each other:

System	What Happens	Result
Inflammatory system	Cytokines and neuropeptides increase local sensitivity	Warmth, swelling, and tenderness
Sympathetic nervous system	Adrenaline/noradrenaline overactivity (“stress response”)	Pain flares with stress or temperature
Sensory cortex	Brain representation of the body becomes blurred	Distorted sensations, loss of control
Limbic system	Emotional centres amplify vigilance and fear	Pain feels threatening and consuming

This creates a self-perpetuating feedback loop between body, brain, and emotion — the hallmark of complex pain.

🧬 Why CRPS Is Unique

In Complex Regional Pain Syndrome, this amplification reaches its peak.Pain can spread beyond the original injury site, accompanied by changes in:

• Temperature and colour (warm to cold phases)

• Sweating and circulation

• Muscle tone, tremor, and weakness

• Skin, hair, and nail growth

Bruehl (2010) describes CRPS as a multi-system disorder involving peripheral inflammation, autonomic dysregulation, and cortical reorganisation — showing just how deeply interconnected the pain experience can become.

🌿 How Healing Happens: Re-educating the Nervous System

The same neuroplasticity that maintains chronic pain can also be used to reverse it.At The Flow Clinic, we use a neuroscience-informed approach to help the nervous system recalibrate.

Our methods focus on:

• Restoring safe sensory input through gentle, graded manual therapy

• Improving interoception and proprioception (the brain’s awareness of the body)

• Calming the autonomic system through breathwork and vagal activation

• Educating and empowering clients to reduce fear and re-establish trust in movement

These interventions work together to teach the nervous system safety again — shifting it from protection back toward connection and flow.

💫 Why Understanding Matters

Pain is not a measure of damage — it’s a measure of perceived threat.When we understand this, pain becomes less frightening, and recovery becomes possible.

Education itself can change the brain’s response — studies show that understanding pain can reduce fear, catastrophising, and pain intensity.That’s why we focus not only on treatment, but also on helping clients make sense of their experience.

✨ Takeaway

Chronic and complex pain conditions remind us that the body, brain, and emotions are never separate. Healing begins not by fighting pain, but by helping the nervous system feel safe again.

Pain is real — but so is recovery.

📚 References

• Bruehl, S. (2010). An Update on the Pathophysiology of Complex Regional Pain Syndrome. Anesthesiology, 113(3), 713–725.

• Moseley, G. L. (2011). Body Illusions in Health and Disease. Oxford University Press.

• Bufacchi, R. J. et al. (2020). Pain outside the body: Defensive peripersonal space deformation in trigeminal neuralgia. Nature Scientific Reports, 7, 12487.

• Strouse, T. (2007). The relationship between cytokines and pain/depression. Psychosomatics.