Stress Overview

Stress, often described as the 'silent killer,' exerts a profound impact on our overall health. While its effects on cognition and mental well-being are widely recognised, the intricate link between stress and our immune response deserves closer attention. The impact of stress on our immune system is so profound that it can make it more difficult for our bodies to ward off diseases.

At its core, stress is a response to perceived threats, a mechanism that prepares our bodies for action, whether in the face of real danger or made-up stress (anxiety). Beyond its mental toll, the relationship between stress and immunity takes centre stage. It's a complex interaction involving hormones, neurotransmitters, and physiological responses.

Chronic stress, in particular, can have long-lasting consequences on our immune system. It triggers a cascade of events at the molecular level, influencing the functioning of immune cells and their ability to defend against illnesses. Additionally, stress can impact our behaviour, leading to unhealthy choices such as poor sleep, unhealthy eating habits, and reduced physical activity, all of which weaken our immune defences.

Take home:

• Stress is a natural response to threats, preparing us for "fight or flight."

• Stressors can be physical, psychological, or emotional.

• Acute stress leads to a rapid adrenaline surge, while chronic stress can have prolonged effects due to the dominant effect of cortisol.

Stress and Immune Suppression

Chronic stress affects our immunity in various ways by over-activating the HPA axis, the hypothalamus-pituitary-adrenals axis.

When your brain senses potential danger or a stressor, the alarm bells ring in the hypothalamus, which swiftly secretes corticotropin-releasing hormone (CRH). As if on cue, the pituitary gland joins the act, releasing adrenocorticotropic hormone (ACTH). This hormone travels through your bloodstream until it reaches the adrenal glands.

Once the adrenal glands receive the signal, they spring into action, actively producing cortisol, your body's primary stress hormone. Cortisol prepares your body for the 'fight or flight' response, a lifesaving mechanism that has ensured our survival as a species.

Take home:

• Chronic stress triggers a complex response through the hypothalamic-pituitary-adrenal (HPA) axis.

• Cortisol, the primary stress hormone, increases heart rate and blood pressure, breathing rate and blood sugar levels for an instant supply of fuel and oxygen for muscle tissue to run away from danger. In the absence of danger, high blood glucose leads to insulin dysfunction over time and can become a triggering factor in metabolic and inflammatory disorders. It also places extra pressure on the digestive system. In the long term, the stress response suppresses the immune system, as the body is not willing to spare any energy.

Cortisol's Influence on Immunity

Cortisol has a direct and profound influence on our immune system.

• Binding to Glucocorticoid Receptors: Cortisol has a keen affinity for glucocorticoid receptors found on immune cells. This liaison sparks a chain reaction that reverberates at the genetic level. Glucocorticoid receptors are specialised proteins located on the surface of immune cells. These receptors act like molecular docking stations, designed to interact with cortisol. When cortisol is released into the bloodstream, it circulates throughout the body, and when it encounters immune cells, it binds tightly to their receptors.

• Gene Expression: Once cortisol docks onto these receptors, it orchestrates which genes are played and which remain silent. This finely tuned symphony of gene expression can either support or dampen immune responses.

• Anti-inflammatory Activity: Cortisol displays anti-inflammatory properties. It does so by suppressing the production of pro-inflammatory cytokines, such as TNF-alpha, IL-6, and IL-1beta, and encouraging the release of anti-inflammatory cytokines like IL-10.

• Immune Cell Distribution: Cortisol also influences the distribution of white blood cells, specifically lymphocytes. Chronically elevated cortisol levels can potentially reduce the number of circulating lymphocytes, impacting the body's defence against infections.

Take home:

• Cortisol binds to glucocorticoid receptors, influencing gene expression.

• Cortisol suppresses pro-inflammatory cytokines and promotes the release of anti-inflammatory cells. The aim of the body is to focus on escape and “suffer” once safe from danger. This explains why you may feel a greater sensation of pain in the late hours when cortisol levels drop at their lowest. Making blood stickier also prevents you from bleeding to death, but reduces oxygenation of tissue and the brain on the long term.

• Cortisol alters white blood cell distribution, potentially reducing lymphocytes.

Chronic Stress and Immunity

While cortisol plays a vital role in the short term, its constant presence due to persistent stress presents significant challenges.

• Desensitisation: Extended exposure to elevated cortisol levels causes immune cells to be less responsive. This phenomenon stems from a decrease in the number of glucocorticoid receptors on these cells, rendering them less sensitive to cortisol's regulatory effects (in the same way too much sugar desensitises cells’ glucose receptor sites, leading to insulin resistance. It is in this way that chronic stress leads to metabolic disorders by keeping blood sugar levels high). This desensitisation essentially weakens the body's ability to mount an efficient immune response when needed. This may explain why many people do not have colds and flu when they are excessively stressed: the activity of their immune cells is suppressed, but get sick once they slow down or go on holiday.

• Chronic Inflammation: As immune cells become desensitised to cortisol, they may veer off course and overproduce pro-inflammatory cytokines. This excess inflammation is a key player in the development of chronic inflammation, which serves as a root cause of numerous inflammatory and metabolic diseases. Conditions such as cardiovascular diseases, diabetes, and autoimmune disorders are closely linked to this persistent state of inflammation.

Take home:

• Prolonged excessive release of cortisol affects immune cells, which may become less responsive.

• Overproduction of pro-inflammatory cytokines can lead to chronic inflammation.

The Impact of Stress on Neurotransmitters

Chronic stress also has a profound influence on neurotransmitters, chemical messengers that regulate countless functions in our body, including your mood and social interactions with others.

• Adrenaline and Noradrenaline: Released from the adrenal medulla, these neurotransmitters are pivotal players in the 'fight or flight' response. When stress strikes, they spring into action, elevating heart rate, increasing blood pressure, and providing a surge of energy. Yet, as stress persists, so does the elevated presence of adrenaline and noradrenaline, which, ironically, can suppress various immune functions, leaving the body more vulnerable to invaders.

• Serotonin and Dopamine: Chronic stress takes a toll on our 'feel good' neurotransmitters, serotonin and dopamine. As their levels decline, it can pave the way for mood disorders. The delicate balance of these neurotransmitters is also intricately linked to the function of immune cells, potentially impairing their ability to defend against threats. The effect of chronic stress on these neurotransmitters creates a very vicious cycle: chronic stress decreases the levels of serotonin and dopamine and low serotonin and dopamine may make you more stressed and anxious, and eat the very food that causes fatigue and weight gain. You feel bad about yourself, you feel more stressed or anxious, and the cycle continues until disease occurs.

Take home:

• Stress influences neurotransmitters like epinephrine (adrenaline) and norepinephrine (noradrenaline), increasing heart rate in the short term but suppressing immune functions in the long term.

• Reduced serotonin and dopamine levels impact immune cell function further.

Resilience and Lifestyle Habits

The profound influence of stress on our behaviour creates a ripple effect, indirectly impacting our immune system:

• Poor Sleep: Stress is a notorious disruptor of sleep patterns. Without restorative sleep, our immune system is weakened further. When stress interferes with sleep, the body's ability to produce cytokines is compromised. Quality sleep is the foundation upon which our immune defences stand.

• Unhealthy Lifestyle Choices: In times of stress, individuals often turn to detrimental coping mechanisms such as smoking, excessive alcohol consumption, or unhealthy eating habits. Sadly, these choices only provide temporary relief. However, they also weaken the immune system over time.

• Reduced Physical Activity: Stress can drain motivation and energy, and it may feel useless to exercise when not too tired to care. Yet, regular exercise is the best form of treatment for stress and is known to support the immune, enhancing the body's defence mechanisms.

Take Home:

Our choices, influenced by stress, indirectly affect immunity:

• Poor sleep due to stress can hinder the production of infection-fighting cytokines.

• Unhealthy habits like smoking and poor diet weaken the immune system.

• Reduced physical activity, caused by stress, can hinder immune function further.

Stress Management and Immunity

Reducing stress is essential to support your mental well-being, your health as a whole and your immunity. There are many techniques you can use to become more aware of your response to certain situations and increase your resilience. Here are some factors to watch out for:

1. Mindfulness and Meditation: Regular meditation, deep breathing exercises, and mindfulness can reduce stress levels, balancing out the immune response.

2. Exercise: Again, physical activity is essential. It helps with the release of endorphins, natural mood lifters, and has direct beneficial effects on immunity.

3. A Balanced Diet: Consuming a diet rich in fruits, vegetables, and whole grains ensures the intake of essential nutrients, antioxidants, and vitamins that support a healthy immune system.

4. Quality Sleep: Ensuring 7-9 hours of sleep allows the body to repair and regenerate, priming the immune system for potential threats. to know how much sleep you need, sleep until you wake up naturally, feeling refreshed, without any alarm.

5. Social Isolation: Stress often leads to withdrawal from social activities and isolation. Loneliness and lack of social support can negatively impact immune function. Studies suggest that social connections play a vital role in immune regulation. Maintaining meaningful relationships and a support system can help counteract this effect.

6. Mental Health: Stress can contribute to mental health issues such as anxiety and depression. These conditions have been linked to immune system dysfunction. Managing stress and seeking mental health support when needed can help mitigate these effects.

7. Slow Healing: Chronic stress can slow down the body's ability to heal from injuries or illnesses. Stress-induced changes in immune function may prolong recovery times post-infection and post-exercise (a key point for professional athletes.

8. Gut Health: Stress can disrupt the balance of beneficial bacteria in the gut, impacting the gut-brain axis. Since a significant portion of the immune system resides in the gut, these disruptions can weaken the body's overall immune response.

9. Hormonal Imbalances: Stress can lead to hormonal imbalances, affecting systems such as the thyroid and adrenal glands. These imbalances can have downstream effects on immune function, as the body requires more vitamin C and magnesium, subsequently depleting stores and leading to deficiencies and dysfunction (many enzymes require magnesium as a cofactor).

10. Ageing and Immunity: Chronic stress may accelerate the ageing process as well as that of the immune system, making it less effective in older individuals. Stress management becomes increasingly important as we age to maintain a robust immune response.

Recognising the link between stress and immunity emphasises the importance of a comprehensive approach to well-being. Prioritising mental health indirectly strengthens our body's disease defence mechanisms. In a world filled with stress, adopting a holistic approach to mind and body becomes evident to support our health and our mental health.

Stress triggers a cascade of physiological responses, including the release of stress hormones like cortisol, which can modulate immune function. Chronic stress, stemming from ongoing challenges and pressures, may lead to a compromised immune system, making the body more susceptible to illnesses.

Strategies like mindfulness, meditation, regular exercise, and quality sleep play a pivotal role in mitigating stress and supporting mental health.

References

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