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Cortisol and the Immune System: How Work-Stress can affect our Down-Time

Updated: Mar 3, 2022

Have you ever embarked on that long-awaited holiday trip after busy times at work, only to find yourself in bed with a full-blown flu? Research shows that the culprit ruining your much-deserved time off may be stress.

Our body is kept in balance by our sympathetic nervous system, which facilitates action, and our parasympathetic nervous system, which facilitates rest and recovery. During stress, we experience pressures that outweigh our coping abilities. As a result, our body senses danger and activates our sympathetic nervous system. This can occur even without our awareness of the stressors. Such activation triggers a cascade of physiological processes to prepare us for a fight-or-flight response to the perceived threat.

The Sympathetic Nervous System: Our Gas Pedal

Neuroscience has revealed how our brain enhances our likelihood of survival by fine-tuning the capabilities of our body upon threat detection. Explicitly, the amygdala, which is involved in fear processing, signals distress to the hypothalamus, which regulates our fight-flight activity. The hypothalamus then stimulates the adrenal glands to release epinephrine (i.e. adrenaline) into the blood stream, raising heart rate, breathing and glucose levels (i.e. blood sugar). These increases drive our body forward like a gas pedal, heightening our energy, alertness and speed.

When the first surge in hormones subsides, the hypothalamus then triggers the hypothalamic-pituitary axis (HPA axis), resulting in the release of the stress hormone cortisol to maintain the stress response in the body. This contributes to prolonged elevation of cortisol levels during on-going stress periods. Chronically increased cortisol can cause great damage to the body as it is pushed to continuously operate above normal energy levels and gets no time to rest and recover. Negative long-term effects include cardiovascular disease (e.g. high blood pressure), digestive issues (e.g. stomach ulcers), and changes in brain functioning (e.g. anxiety, depression).

The Let-Down Effect: Our Holiday Killjoy

During short stress, cortisol aids our survival by increasing immuno-functioning and pain tolerance, protecting our body from slowing down through illness, infection or injury while we are running for our lives. Those effects are comparably sustained when we are affected by chronic stress.

So, what happens to our body when we take a break after weeks of chronic stress? Research terms it the let-down effect: As soon as the body realizes the absence of stress, we experience an abrupt drop in cortisol levels. The sudden withdrawal of cortisol affects various physiological system, the most relevant for our holiday time being the immune system. Our stress-fuelled, chronically enhanced immuno-functioning now dives far below a healthy level, making us significantly more susceptible to pathogenic invasion. We often contribute further to this vulnerability on our time off, when instinctively trying to increase the levels of our happy hormone dopamine by indulging in greasy comfort food or a glass of wine.

The Parasympathetic Nervous System: Our Brake

The Solution!

Importantly, scientists indicate that we protect ourselves from these stress-related effects through both prevention and after-care.

In terms of prevention, we can keep cortisol levels balanced by scheduling brief breaks throughout the day. In particular, a few minutes of diaphragmatic breathing, mindfulness and visual imagery several times during the day have been shown to effectively activate our parasympathetic nervous system, allowing us to pull the brake and give our bodies the opportunity to recover.

In terms of after-care, research highlights the importance of facilitating a slow cortisol come-down, equivalent to a cooling-off period after vigorous exercise. For example, engaging in physical and mental stimulation with gradually declining intensity for at least three days after high-stress periods permits the body to reduce cortisol levels slowly over time.

This can include light exercise, challenging puzzles or creative tasks. Ultimately, while we like to think of work and fun as separate, our bodies need to be looked after during our work-time, to ensure that we can fully enjoy our holiday-time.

For more information or to book a consultation with psychologist Dr. Esslin Terrighena, please contact (852) 2521 4668 or

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