“It was scientifically embarrassing to suggest the existence of a connection between the brain and the immune system. The immune system stopped at the neck”
– Dr Monty Lyman (The Immune Mind, 2024).
Until very recently, it was thought that the brain and immune system, whilst being very similar, acted in separation. No crossover could be identified and so it was assumed that they didn’t communicate, didn’t work together, and weren’t connected. New evidence is increasingly revealing a clear link between these systems – connected, communicative, cohesive.
Independent but similar: what we already knew
Both the brain and the immune system are thought of as independent parts of our body. Our brain is an organ that focuses on organisation and control of our minds and bodies, while our immune system is there to provide defense against a microbial world to protect the functioning of our body.
This is how they are different, but there are also a number of similarities and ways in which the brain and the immune system are aligned …
01 | Shared Goals
Our brain is primarily focused on survival, through interpreting sensations, controlling our behaviour and learning from past experiences. The goal of our immune system is not identical, but undoubtedly linked. Our immune system is focused on defence: defending the body against infection and protecting our overall health.
02 | Self vs Non-Self
Both our brain and our immune system are working to separate the self from anything alien in our body or in our environment. They are tasked with differentiating between the threatening around us and the non-threatening within us, and acting accordingly.
03 | Learning and Memory
Lyman (2024) says of the immune system and the brain “whether dealing with the massive or the microscopic, their job is to recognise, react and remember.” Both systems are tasked with learning from threats and near-misses that have occurred before, and retaining this information for future use.
New evidence: a connection between the brain and the immune system
One of the primary ways that the immune system attracts attention, on a cellular level, to help bolster and support its defenses is through inflammation. We can think of inflammation as a kind of flare, sending out a signal for more help in a particular area.
When the body has activated an immune system response, we now know that it’s very likely that the brain is learning from the body and creating its own immune system reaction. This is why, when fighting illness, infection or injury, we often end up experiencing emotional and cognitive changes beyond just the typical ‘sickness behaviours’ (a term coined by Twaddle, 1979) like curling up on the sofa, craving rest and avoiding others. We can also experience inflammation in the central nervous system that affects and impacts both our thinking and feeling space.
Why does any of this matter?
Our immune system works very hard! In fact, it’s always working against potential illness and virus and infection around us. This new knowledge, further reinforcing the brain-body link in ways that we had little awareness of before, means that this immune system fight could be having a big impact on our mood states, concentration, memory and on our behaviour due to inflammation in the brain.
The role of psychological stress in immune functioning
Psychological stress has been linked to inflammation, unbalanced gut microbiome and an increased risk of autoimmune disorder (Lyman, 2024).
Whilst not all stress is bad, chronic and intense stress can have a negative impact on our immune functioning.
When our brain perceives a situation as threatening it releases stress hormones such as epinephrine and norepinephrine which trigger our ‘fight or flight’ response. This activates increases in our heart rate and blood flow, increased oxygen consumption, greater alertness and improved focused cognition. Essentially our body is getting ready to ‘fight’ the potential threat or flee the situation altogether. Following this, a further stress hormone – cortisol – is also released. This boosts blood glucose levels for increased energy and faster reaction times.
In small doses, these stress hormones serve an important purpose in working to protect us from harm. Our body is also very good at recovering quickly from a needed stress reaction. However, activated persistently and chronically, there can be a negative toll on our body’s organs and issues, “and can impact intestinal functions, cardiovascular functions and the immune system” (Global Autoimmune Institute, 2024).
Chronic stress is thought to both trigger and exacerbate autoimmune conditions, such as rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease, multiple sclerosis, Graves’ disease, type 1 diabetes and psoriasis.
An increased awareness of what triggers symptoms can help to alleviate autoimmune flares or prevent them from worsening. “Psychological and cognitive behavioral therapy aimed to reduce stress levels has also been shown to be effective in influencing better outcomes for many autoimmune diseases” (Global Autoimmune Institute, 2024).
How can we explain individual differences?
“When you get infected or inflamed, your brain is activated as much as your immune system is, and rapid neurological changes occur.” (Lyman, 2024)
→ You slow down, both mentally and physically
→ You focus inwards on what is happening inside your body
→ You withdraw and isolate from others
→ You become more sensitive to negativity
→ You become less sensitive to reward and positivity
→ You over-exaggerate perceived threats
For some people, this can trigger a pattern of ‘stuckness’ within the loop of sickness behaviour, which includes increased sensitivity to physical pain and greater mental struggle. For others, the sickness behaviour is temporary and appears to lift with relative ease.
Why is it that some get stuck in this downward spiral, whilst others do not?
There is currently no definitive answer to these individual differences. Lyman (2024) suggests that perhaps chronic inflammation “lingers in the body and brain” longer for some, or perhaps in some cases it is simply “the straw that broke the camel’s back” where a buildup of previous psychological stress, genetic factors, or past trauma overwhelm the system with the newest issue.
Conclusion
This new understanding of the connection between the brain and the immune system, that there could be inflammation having an impact neurologically, opens up a whole other area of exploration for those that need support with chronic health conditions.
If you work with patients who are living with chronic pain or other chronic stress conditions, Healthy Mind Psychology offers guidance and strategies to empower individuals to manage their response to pain or other symptoms, whether that’s the signal itself or all the implications these symptoms have on one’s overall quality of life.
References
Global Autoimmune Institute. (2024, June, 3). Stress & autoimmune disease: navigating the complex relationship. Retrieved (August, 16, 2024) from www.autoimmuneinstitute.org/articles/stress-autoimmune-disease-navigating-the-complex-relationship/
Lyman, M (2024). The Immune Mind: The hidden dialogue between your brain and immune system.