What is psychoneuroimmunology? How stress and the immune system are connected

By Dr. Abel O. Bernard,Principal Clinician, Naturopathic Practitioner
Published 9 November 2026 · Updated 9 November 2026· 5 min read

What psychoneuroimmunology means

Psychoneuroimmunology, usually shortened to PNI, is the study of how the mind, the nervous system and the immune system affect one another. The name joins three ideas: psycho (thoughts, emotions and behaviour), neuro (the brain and nerves) and immunology (the body's defences).

The central idea is simple. These systems are not separate. They share chemical messengers, including hormones, nerve signals and immune molecules called cytokines, so what happens in one can influence the others.

How stress and the immune system communicate

When you face a threat, the body activates the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis, which release stress hormones such as adrenaline and cortisol. These pathways are also linked with changes in the immune system, including changes in markers of inflammation. [2]

Timing matters. A meta-analysis of three decades of research found that short-term stress tends to prime parts of the immune system, which can help the body respond to injury or infection, while long-lasting stress was associated with broader suppression of immune function. People who were older or already unwell appeared more vulnerable to these changes. [1]

One caution is important. The authors of that analysis noted that it remains an open question how far these measured immune changes lead to more illness in otherwise healthy people. [1]

What research says about mind-body practices

Researchers have asked whether practices such as mindfulness meditation, yoga, tai chi and qigong change immune markers. A 2014 meta-analysis of controlled trials found that mind-body therapies reduced markers of inflammation and influenced immune responses to vaccination, with minimal evidence of effects on other resting immune measures. [2]

A later systematic review of randomised trials of mindfulness meditation found possible effects on some markers of inflammation, cell-mediated immunity and biological ageing. It described the results as tentative and in need of replication, and noted that studies differed widely in the people studied, the design and the laboratory methods. [3]

A 2022 meta-analysis pooled trials of mindfulness-based interventions across six immune-related markers, including C-reactive protein, interleukin-6, CD4 cells and nuclear factor-kappa B. [4]

Taken together, the findings point in a consistent direction: mind-body practices can lower markers of inflammation and shape immune responses. Researchers are still working out which of these changes matter most for health.

What this does not mean

• It does not mean you can boost your immune system. The immune system is a balanced network, and more activity is not always better.
• It does not mean stress causes any particular disease, or that being ill is a failure of positive thinking.
• It does not mean a mind-body practice can replace vaccination, medicines or medical care.
• It does not mean that results are guaranteed. People respond differently.

Practical steps that fit the evidence

PNI does not offer a secret treatment. It gives a reason to take everyday habits seriously. These are general suggestions that carry low risk for most people. They are not individual medical advice.

• Protect your sleep by keeping regular sleep and waking times.
• Build a short daily practice of slow breathing, relaxation or mindfulness, even five to ten minutes.
• Move your body regularly in ways you enjoy.
• Eat regular, balanced meals using foods you know and can afford.
• Keep supportive people around you, because social support is part of how we cope with stress.
• Keep up with vaccinations, check-ups and prescribed medicines.

How this fits our care at McSara

At McSara, we use PNI as a way of organising care and not as a single treatment. We look at stress, sleep, mood, nutrition, movement and support together, and build a plan of practical steps with you. We are open about what the research does and does not show, and we do not promise results.

When to see a doctor

Please see a doctor if you have any of the following, whatever your stress levels:

• A fever that does not go away
• Weight loss that you cannot explain
• Frequent or serious infections
• Low mood or anxiety that is severe or lasting
• Thoughts of harming yourself. Please contact a doctor, a mental health professional or someone you trust today, or go to the nearest hospital emergency department.

References

1. Segerstrom SC, Miller GE. Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychological Bulletin. 2004;130(4):601-630. Source
2. Morgan N, Irwin MR, Chung M, Wang C. The effects of mind-body therapies on the immune system: meta-analysis. PLoS ONE. 2014;9(7):e100903. Source
3. Black DS, Slavich GM. Mindfulness meditation and the immune system: a systematic review of randomized controlled trials. Annals of the New York Academy of Sciences. 2016;1373(1):13-24. Source
4. Dunn TJ, Dimolareva M. The effect of mindfulness-based interventions on immunity-related biomarkers: a comprehensive meta-analysis of randomised controlled trials. Clinical Psychology Review. 2022;92:102124. Source