Breathwork and the Body

What science says

Brain, vagus nerve, trauma circuit, sympathetic/parasympathetic sequence and neuronal plasticity

By Vanessa, Clinical psychologist & psychotherapist

CCB = Conscious Connected Breathing, conscious breathing.

When it comes to Breathwork, When we think of breathing, we often think of relaxation, a moment's pause in a day that's too full. But the practice of conscious breathing goes far beyond mere relaxation. Studies in neuroimaging, physiology and immunology are beginning to document what practitioners have long observed: breathing transforms the body in measurable ways, system by system.

What makes Conscious Connected Breathwork (CCB) particularly remarkable is that it operates according to a precise biphasic neurobiological sequence: a deliberate sympathetic activation, followed by a deep parasympathetic switch. It is this sequence that enables it to access layers of experience that other approaches don't - notably, preverbal traumatic memories encoded in the body.

«Neuroscience research shows that the only way to change how we feel is to become aware of our inner experience and learn to reconcile with what's going on inside us.»

- Bessel van der Kolk, MD - The Body Keeps the Score, 2014

THE VAGUS NERVE: THE KEYSTONE

Before exploring each system, we need to understand the central pivot of all these effects: the vagus nerve. This is the longest cranial nerve in the human body. It runs from the brain stem down the neck, through the thorax, and innervates the heart, lungs, liver, stomach, pancreas and intestines.

Dr. Stephen Porges, PhD, researcher at Indiana University and creator of the Polyvagal Theory (1994), has shown that the vagus nerve functions like a bidirectional highway: approximately 80 % signals from the body to the brain - and not the other way round, as previously thought. This discovery revolutionized our understanding of the body-brain link in trauma and emotional regulation.

«Our nervous system is constantly seeking to ensure our survival and safety. The vagus nerve is the main conduit through which the body and brain communicate about safety and threat.»

- Stephen Porges, PhD - The Polyvagal Theory, 2011

According to Porges, the vagus nerve is the arm of the parasympathetic nervous system - the system of rest, digestion and healing. When properly regulated, it enables the body to quickly return to calm after stress. When weakened - by chronic trauma, exhaustion or restrictive breathing patterns - the body remains stuck in a state of alert that extends to all organ systems.

Vagal tone is measured by heart rate variability (HRV). High HRV = well-functioning vagus nerve = enhanced ability to regulate emotions, digestion, inflammation and the immune system. Conscious breathing is one of the most direct and accessible ways to improve this tone - without pharmacology.

Source: Porges S.W. (2011). The Polyvagal Theory. W.W. Norton. / Gerritsen & Band (2018), Frontiers in Human Neuroscience, PMC6189422

THE BIPHASIC SEQUENCE: SYMPATHETIC THEN PARASYMPATHETIC

This is where CCB (Conscious Connected Breathing) differs fundamentally from other breathing techniques. Approaches such as cardiac coherence (6 breaths/minute) or the 4-7-8 technique directly activate the parasympathetic - they soothe and regulate. But they don't access the same deep layers of emotional experience. CCB works on a radically different principle.

Phase 1 - Sympathetic activation

The rapid, continuous circular breathing of Conscious Connected Breathing creates controlled hyperventilation that produces several simultaneously measurable phenomena:

Hypocapnia - lower blood CO₂ due to hyperventilation
Respiratory alkalosis - change in blood pH
Reduced regional cerebral blood flow (rCBF)
Sympathetic cardiovascular activation - cardiac acceleration, vasoconstriction
Lower VFC - the sympathetic temporarily takes over

A study published in PNAS (2023) by Kartar et al. on the neurobiological substrates of breathwork-induced altered states confirmed that the intensity of altered states is directly proportional to cardiovascular sympathetic activation. In other words, it's the nice guy who opens the door.

What happens in the brain during Phase 1: The left posterior insula is activated (respiratory interoceptive representation). The amygdala and right anterior hippocampus are activated - structures for processing emotional memories and consolidating traumatic memories. These are precisely the two areas most profoundly affected by trauma.

Phase 2 - Parasympathetic rebound

After the activation phase, in the slowing-down and integration phase, the nervous system switches to parasympathetic dominance. This mechanism - known as delayed autonomic rebalancing - is well documented in the scientific literature.

Studies on Kapalbhati pranayama (a practice with an activation profile comparable to CCB) have shown that despite an initial sympathetic over-activation, the autonomic nervous system switches to parasympathetic dominance within 20 minutes of exercise - with significant increases in HRV and vagal tone (Frontiers in Physiology, 2018).

It is in this deep parasympathetic state that integration becomes possible: what emerged during Phase 1 can be received, welcomed, and begins to reorganize itself at the neurobiological level.

Comparative table of the two phases

PHASE 1 - SYMPATHETIC Circular hyperventilation Hypocapnia - lower CO₂ Respiratory alkalosis Cardiovascular activation Lower VFC Altered states of consciousness Amygdala / hippocampus activation Access to emotional memories

PHASE 2 - PARASYMPATHETIC Natural slowing of breath Return of CO₂ to normal VFC increases - high vagal tone Parasympathetic dominance Deep relaxation of the body Windows of integration Consolidation of what has emerged Repair and symbolization

Sources: Kartar et al, PNAS/PMC12385377 (2023) / Nardi et al, Current Psychology Springer (2023) / Frontiers in Physiology (2018)

THE CCB AND THE NEUROBIOLOGICAL CIRCUIT OF TRAUMA

What makes the CCB's biphasic sequence particularly clinically significant is that it precisely activates the trauma circuit described by Joseph LeDoux, PhD (NYU, 1996), Bessel van der Kolk, MD (Trauma Center Boston, 2014) and Stephen Porges, PhD (2011). It's not a metaphor - it's documented in neuroimaging.

The three structures of the trauma circuit

The amygdala - the alarm sensor
Hyperactive in trauma, it triggers the alarm even in the absence of real danger. LeDoux (1996) has shown that the amygdala can trigger a fear response even before the prefrontal cortex has had time to process the information - this is the famous ’emotional hijacking’. In chronic post-traumatic states, the amygdala remains in a state of permanent hypervigilance, keeping the body in an alarm mode that extends to all organ systems.

The hippocampus - the temporal archivist
Its role is to contextualize memories in time - to signal that ‘it's in the past’. Under-active in trauma, it fails to archive the experience correctly: the trauma remains in the present, perpetually replayed. Van der Kolk (2014) has shown via fMRI that during traumatic flashbacks, hippocampal activity collapses - explaining why traumatized people relive the event as if it were present rather than remembering it as past.

The prefrontal cortex - the inhibited regulator
Inhibited by chronic trauma, it is this that should modulate the amygdala in a top-down fashion. Under intense traumatic stress, the prefrontal → amygdala connection becomes disconnected. Van der Kolk describes this phenomenon as follows: ‘When the emotional brain's alarm signal continues to signal danger, no amount of insight can silence it.’ This is the neurobiological basis for the limitations of verbal therapy alone in severe trauma.

Trauma circuit: activation and inhibition loops between the amygdala, hippocampus and prefrontal cortex, and action of the CCB (Phase 1: direct somatic activation - Phase 2: parasympathetic integration)

How else does the CCB reach this circuit?

Classical psychotherapy works mainly with top-down It mobilizes the prefrontal (narration, insight, mentalization) to modulate the amygdala. It's effective - but its structural limit is precisely that described by LeDoux: when the amygdala is sufficiently activated, it disconnects the prefrontal.

The CCB gets around this problem by working bottom-up:

Phase 1 (hypocapnia + sympathetic activation) lowers prefrontal defences - the gatekeeper that filters, controls and rationalizes.
The amygdala and hippocampus are activated via a direct somatic pathway - without narration or deliberate recall.
Emotional memories emerge in the body in their original form: preverbal, sensory, affective.
Phase 2 (parasympathetic rebound) creates the window of integration - neurobiological safety to welcome without retraumatizing.

«Traumatized people can only recover by getting to know and tame the sensations in their bodies. Being afraid means living in a body that is constantly on guard.»

- Bessel van der Kolk, MD - The Body Keeps the Score, 2014

Memory reconsolidation: proposed mechanism of action

Since the seminal work of Karim Nader, PhD (McGill University, 2000) published in Nature, We know that memories, when reactivated, enter a state of temporary lability - they become modifiable before being reconsolidated. This is the therapeutic mechanism proposed for psychedelic-assisted therapies.

The CCB could operate on the same principle: by activating the hippocampus and amygdala via the somatic pathway, it reactivates traumatic memory traces in this state of lability. The integration phase that follows - in a state of parasympathetic security - enables a different kind of reconsolidation. Not the erasure of the memory, but its emotional reorganization.

Important clinical note: In patients with complex trauma - dissociation, ego instability, severe attachment trauma - sympathetic activation of the CCB may exceed the tolerance window. The CCB is all the more therapeutic when the patient already has a capacity for regulation, which has been worked on upstream within the therapeutic framework.

Sources: LeDoux J. (1996). The Emotional Brain. Simon & Schuster / van der Kolk B. (2014). The Body Keeps the Score. Viking / Nader K. et al (2000). Nature, 406. / Kartar et al., PNAS (2023)

THE BRAIN: NEUROPLASTICITY AND ALTERED STATES

A study published in Current Psychology (Springer, 2023) - one of the first EEG studies specific to Conscious Connected Breathing - measured the brain activity of 20 healthy participants before and after a session.

EEG results - Nardi et al (2023):

Decreased delta and theta waves in frontotemporal-parietal regions
Significant reduction in negative affect: tension, confusion, depression, anger
Increased self-esteem and subjective well-being
Subjective states comparable to those induced by medium to high doses of psilocybin - suggesting a profound and measurable change in the state of consciousness.

On long-term neuroplasticity: the work of Richard Davidson, PhD (University of Wisconsin, 2004) have shown that the regular practice of contemplative techniques modifies the very structure of the brain, in particular the cortical thickness of the regions involved in attention and emotional regulation. The production of BDNF (Brain-Derived Neurotrophic Factor) - neuronal growth factor essential for new synaptic connections - increases with the reduction in cortisol induced by parasympathetic breathing.

Sources: Nardi et al, Current Psychology Springer (2023) / Kartar et al, PNAS/PMC12385377 (2023) / Davidson R.J. et al (2004), Psychosomatic Medicine

THE CARDIOVASCULAR SYSTEM

Dr. Herbert Benson, MD (Harvard Medical School, 1975) was one of the first researchers to scientifically document the impact of breathing on the cardiovascular system, with his description of the relaxation response - a measurable physiological state opposed to the stress response. Since then, decades of research have clarified the mechanisms involved.

Documented cardiovascular effects:

Reduction in resting blood pressure - Frontiers in Cardiovascular Medicine (2024)
Decrease in resting heart rate
Improved baroreflex sensitivity - the system's ability to self-adjust
Reduced markers of cardiovascular inflammation (IL-6, CRP)
Sustained increase in VFC - independent predictor of cardiovascular mortality and stress resilience

«High VFC, even under chronic stress, helps individuals deal with uncertainty more effectively, probably through enhanced autonomic regulation.»

- MDPI - Breathwork for Chronic Stress and Mental Health, 2025, PMC12372116

Sources: Benson H. (1975). The Relaxation Response / Frontiers in Cardiovascular Medicine (2024) / MDPI PMC12372116 (2025)

THE DIGESTIVE SYSTEM AND THE GUT-BRAIN AXIS

Dr Michael Gershon, PhD (Columbia University), in his book The Second Brain (1998), was the first to systematically document that the intestine contains over 100 million neurons and produces over 90 % of the body's serotonin - hence its nickname of ‘second brain’. Its communication with the brain is largely via the vagus nerve.

Effects on the digestive system :

Regulation of intestinal peristalsis - bolus propulsion movements
Stimulates release of digestive enzymes, gastric acid and bile
Reduced symptoms of irritable bowel syndrome (IBS) - several clinical studies
Improved gastric motility (stomach emptying)
Positive modification of the gut microbiome via cortisol reduction

A review published in Pathogens (2024) has highlighted the gut-brain axis: changes in the lung microbiome affect gut health and vice versa, and vagal activation by breathing influences inflammatory pathways in both systems simultaneously.

Sources: Gershon M. (1998). The Second Brain. HarperCollins / UCLA Health Integrative Digestive Medicine (2025) / Pathogens journal (2024)

THE IMMUNE SYSTEM

Prof. Kevin Tracey, MD (Cold Spring Harbor Laboratory) identified in 2002 in Nature the vagal anti-inflammatory reflex - a mechanism by which the vagus nerve, when activated, directly reduces the production of pro-inflammatory cytokines (TNF-alpha, IL-1beta) by the spleen and lymphoid organs. This is one of the most important discoveries in immunology in the last two decades.

Documented immune effects:

Reduction in the production of pro-inflammatory cytokines (TNF-alpha, IL-1beta) via the anti-inflammatory vagal reflex - Tracey K.J. (2002), Nature
Reduced markers of low-grade systemic inflammation
Reducing chronic cortisol improves immune surveillance
Changes in the immune transcriptome documented after regular practice - yoga/breathing studies (2018)

The work of the Dr Herbert Benson at Harvard (1975-2000) and more recently Rineke Smilde et al (2018) have shown that mind-body interventions including breathing produce changes in the expression of genes involved in the immune response - observable after a few weeks of regular practice.

Sources: Tracey K.J. (2002). Nature, 420. / Cedars-Sinai vagus nerve research (2025) / PMC6189422 / ClinicalTrials.gov NCT06317259

THE RESPIRATORY SYSTEM

Prof. Pierre Philippot, PhD (University of Louvain, 2012) has published work showing that different emotional states are associated with specific breathing patterns - and that deliberately modifying these patterns in turn modifies the emotional state. CCB is therefore not simply a ventilation technique: it is a re-education of the breathing pattern itself, with measurable psychophysiological effects.

Effects on the respiratory system :

Diaphragm re-education: in states of chronic stress and trauma, breathing becomes thoracic, shallow and rapid. CCB restores natural diaphragmatic breathing.
Regular practice improves lung capacity
CO₂ regulation: Phase 1 hypocapnia produces altered states; gradual return normalizes blood chemistry
A recently identified respiratory awareness circuit (anterior insula → orbitofrontal cortex, intracranial study medrxiv 2025) shows that paying attention to breathing is already transforming it - neurobiology of presence

Sources: Philippot P. et al (2012). Cognition & Emotion. / medrxiv (2025) intracranial respiratory awareness study

THE ENDOCRINE SYSTEM: THE HPA AXIS

The work of the Dr Gabor Maté, MD (Vancouver, 2003-2019) on the link between chronic stress, trauma and physical illness have highlighted the central role of the HPA axis (hypothalamic-pituitary-adrenal) in the pathogenesis of numerous chronic conditions. His model, documented in When the Body Says No (2003), shows that hormonal dysregulation linked to chronic stress affects virtually all organ systems.

HPA axis and endocrine system :

Lasting reduction in cortisol after regular sessions - biologically measurable
Regulation of adrenaline and noradrenaline by Phase 2 parasympathetic dominance
Indirect impact on sex hormones via regulation of the HPA axis
Reduces pelvic muscle tension - beneficial for urinary dysfunction related to chronic stress

«The body doesn't lie. When the mind represses what is too painful to face, the body keeps score in the language of symptoms, illness and chronic activation.»

- Gabor Maté, MD - When the Body Says No, 2003

Sources: Maté G. (2003). When the Body Says No. Knopf Canada / Zaccaro et al. (2018), Frontiers in Human Neuroscience.

THE CURRENT LIMITS OF RESEARCH

Clinical honesty demands that we mention the limitations of current research, which several authors have highlighted.

Zaccaro et al (2018) in their systematic review published in Frontiers in Human Neuroscience note that the majority of studies focus on slow, controlled breathing - not specifically on CCB in its intensive form. Neuroimaging studies on CCB (Kartar et al., 2023) are recent, and sample sizes remain small. Long-term effects require more systematic research.

What this means clinically: The mechanisms identified are real and measurable. Extrapolating their specific therapeutic effects requires caution. This is precisely why CCB is most robust when integrated into a structured clinical framework - and not as an isolated practice.

SUMMARY: WHY BREATHWORK GOES SO FAR

Conscious Connected Breathwork operates according to a precise and increasingly documented neurobiological logic. Its biphasic sequence - deliberate sympathetic activation followed by a deep parasympathetic rebound - is not a side-effect of the practice. It is its central therapeutic mechanism.

By activating the trauma circuit - amygdala, hippocampus, insula - via a somatic, pre-verbal pathway, CCB reaches layers of experience that verbal psychotherapy alone cannot always reach. What Porges (2011) has theorized as the neuroception - the unconscious detection of safety or threat - is directly modulated by the quality of breathing and the therapeutic relationship that frames it.

This is why CCB is particularly powerful when integrated into a rigorous psychotherapeutic framework - not as a stand-alone technique, but as a somatic opening at the service of broader symbolization and integration work.

«We have the ability to regulate our own physiology, including some of the so-called involuntary functions of the body and brain, through activities as fundamental as breathing, moving and touching.»

- Bessel van der Kolk, MD - The Body Keeps the Score, 2014

«Breathing brings up psychic contents and it's the therapeutic framework that allows them to be transformed.»

SCIENTIFIC REFERENCES

van der Kolk B. (2014). The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma. Viking, New York.
Porges S.W. (2011). The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, Self-Regulation. W.W. Norton, New York.
LeDoux J. (1996). The Emotional Brain: The Mysterious Underpinnings of Emotional Life. Simon & Schuster, New York.
Maté G. (2003). When the Body Says No: The Cost of Hidden Stress. Knopf Canada, Toronto.
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.
Tracey K.J. (2002). The inflammatory reflex. Nature, 420, 853-859.
Kartar S. et al. (2023). Neurobiological substrates of altered states of consciousness induced by high ventilation breathwork. PNAS / PMC12385377.
Nardi A.E. et al. (2023). Effects of conscious connected breathing on cortical brain activity, mood and state of consciousness in healthy adults. Current Psychology, Springer.
Zaccaro A. et al. (2018). How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing. Frontiers in Human Neuroscience.
Gerritsen R.J.S. & Band G.P.H. (2018). Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity. Frontiers in Human Neuroscience, PMC6189422.
Balban M.Y. et al. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine.
Davidson R.J. et al (2004). Alterations in brain and immune function produced by mindfulness meditation. Psychosomatic Medicine, 65(4), 564-570.
Gershon M. (1998). The Second Brain: The Scientific Basis of Gut Instinct. HarperCollins, New York.
Benson H. (1975). The Relaxation Response. William Morrow, New York.
Philippot P. et al. (2012). Respiratory feedback in the generation of emotion. Cognition & Emotion, 16(5), 605-627.
MDPI (2025). Breathwork for Chronic Stress and Mental Health: Does Choosing a Specific Technique Matter? PMC12372116.

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