Among all the factors that contribute to mental health issues, the most significant one is stress. For a majority of people with mental health issues, stress is part of their lives, whether it’s a contributor or a related symptom.

What is stress?

Stress is a physical, mental, or emotional factor that causes bodily or mental tension.MedicineNet. (2016). ‘Medical definition of stress’. [online] Available at: [accessed 26 Oct. 2017].

In biochemical terms, stress is a state of real or imagined threat to our homeostasis (the balance of our bodies’ functions).Smith, S., Vale, W. (2006). ‘The role of the hypothalamic-pituitary-adrenal axis in neuroendocrine responses to stress’. [online] Dialogues in Clinical Neuroscience, 8(4), pp.383–395. Available at: [accessed 30 Aug. 2017].

Stress is caused by what we call ‘stressors’: the events or conditions that make us stressed. These can be psychological (anger, bereavement, trouble at work), or physical (dieting, over-exercising, dehydration). Either way, our bodies react with the same physiological response. They release stress hormones, and these cause a range of other changes.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.154.

Stress is subjective

One of the most important things to remember about stress is that it’s subjective. The same event or circumstance might feel especially stressful to some people, but less so to others.

Our response to stressors depends on a range of factors, including:

  • Our genetics
  • Our thoughts and beliefs
  • Our personality
  • Our biology
  • Our underlying state of health

Shawn Talbott sums it up: someone is suffering from chronic stress, he says, when the “daily demands” on them are greater than their “coping resources and/or support system”.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.109.

How our bodies respond to stress

When our bodies feel under stress, they trigger a ‘stress response’.

This is controlled by the HPA axis (hypothalamus-pituitary-adrenal). It sets off a chain reaction, including the release of stress hormones, and a range of subsequent effects.

The ‘stress response’ is a combination of factors.

Stress is regulated by both the limbic (complex) and ‘reptilian’ (instinctive) parts of our brains. They perceive the stressor as a threat, and they trigger a biochemical response often called ‘fight or flight’. This primes our bodies to fight or flee from the stressor.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p. 93.

A variety of effects are produced, involving our endocrine, nervous, and immune systems.Smith, S., Vale, W. (2006). ‘The role of the hypothalamic-pituitary-adrenal axis in neuroendocrine responses to stress’. [online] Dialogues in Clinical Neuroscience, 8(4), pp. 383–395. Available at: [accessed 30 Aug. 2017].

The stress response causes the sympathetic nervous system and HPA axis to respond, releasing the stress hormones cortisol and adrenaline.Ulrich-Lai, Y.M. and Herman, J.P., 2009. Neural regulation of endocrine and autonomic stress responses. Nature reviews neuroscience, 10(6), p.397.

These hormones:Talbott, S. (2002). The Cortisol Connection. 2nd ed. Alameda, CA: Hunter House, pp.105–107.

  • Increase our blood sugar, so that we have more energy to fight or flee
  • Increase our blood pressure and heart rate, to pump more blood through our limbs
  • Increase our breathing rate, to give us more oxygen
  • Slow down our digestion, so that we have as much blood as possible in our limbs (the opposite of ‘fight or flight’ is ‘rest and digest’)
  • Slow down our immune system, so that we can focus on the immediate danger rather than pre-existing problems

Cortisol is the most important of the two stress hormones. In a flexible and adaptive stress response, our cortisol levels will keep observing our natural rhythms (higher in the morning, lower at night), and will drop once the danger has passed.

But when our bodies are unable to respond healthily to stress, by effectively releasing or decreasing cortisol levels — when they can’t move between ‘fight and flight’ and ‘rest and digest’ — the continued stress can lead to physical and mental health issues.

Our bodies are designed to withstand temporary, acute stress. Once the stressor has been dealt with, our hormones and bodily functions can go back to their state of equilibrium. This allows our bodies to rest, digest, and repair themselves.

But if this isn’t possible, or the stressor keeps reappearing in our lives, we may be affected by ‘chronic stress’.

Chronic stress

Some modern stressors are chronic and unrelenting, and it’s hard to fight or escape them. Many of these centre on urban living, such as the stress of commuting, the stress of time pressure, the stress of financial problems, and so on.

We respond to psychological stress, from irrational fears about the future to anger about the past, in the same way as physical stress. When the problem isn’t something our bodies can heal, the stress can become unrelenting.

This leads to our stress response being chronically activated. Persistently high levels of stress hormones can cause an imbalance in the HPA axis and contribute to mental health problems:Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, pp.3032

  • A constant release of stress hormones can limit the time our bodies and minds get to relax
  • Chronically high levels of cortisol can lead to cortisol resistance and burnout
  • People with chronic stress diseases often exhibit a ‘flat’ cortisol rhythm; these people can include
    • Those with chronic fatigue syndrome
    • Those with fibromyalgia
    • Those with depression
    • Those suffering from PTSD
    • Those who’ve suffered physical abuse

Contributors to stress

Stress is endemic in our modern societies. Many of us have busy, hectic, and demanding lifestyles; we juggle commitments to our work, our families, our friends, our hobbies, our communities, and so on.

According to a 2012 survey for the UK Health and Safety Executive:Woodrow, S. (2012). ‘Stress, the facts’. [online] Stressuless. Available at: [accessed 22 Nov. 2017].

  • Nearly five million people described themselves as ‘very’ or ‘extremely’ stressed at work
  • Nearly half a million people had work-related stress that resulted in absence through illness
  • ‘Stress, depression, and anxiety’ were the second most common work-related illnesses (after back problems)

There are a large number of possible stressors in modern life. Some of these are suggested below:

A range of lifestyle problems can contribute to our stress levels:

Chronic lifestyle issues can also cause us stress. These can take the form of:

  • Allergies
  • Obesity
  • Addiction
  • Chronic illness

A range of difficulties at home or in other areas of our personal lives can contribute to our stress levels:

  • Having too little time alone
  • Having too much time alone (loneliness)
  • Fractious relationships (tension, frequent arguments)
  • Being socially isolated or excluded from our communities
  • Poor housing and/or facilities
  • Noise and/or pollution
  • Living in urban environments

Read more about how personal circumstances can impact our mental health:

Stress is often caused by problems in the workplace, or trouble holding down a job.

Some common issues include:

  • Being overworked
  • Being bullied at work
  • Being underpaid, or getting into financial difficulties
  • Competition with, or demands from, colleagues/rivals
  • Inconvenient connections with different time-zones
  • Being unemployed

Even when work isn’t causing us problems, it can become a source of stress. People overcommitted to their work have been shown to have elevated levels of stress and cortisol.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.37.

Some individual events are significant enough to trigger chronic or long-term stress on their own.

And if they worry us enough, it doesn’t matter whether they’re positive or negative things: they can still become stressors.

For instance, we might:

  • Move house, or lose our home
  • Change or lose our job
  • Have, or adopt, a child
  • Get married, or divorced
  • Suffer the death of a friend or family-member

Stress is a matter of what our bodies perceive. They respond the same way whether the threat is real or imagined.

This means that our expectations, thoughts, and beliefs can also generate a physical stress response.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.29.

Negative expectations, thoughts, and beliefs

One common trigger of stress responses is our imagination: how we worry about the past, and what we expect in future.

Often these worries are to do with our sense of agency and control. For instance, we might worry that we’ve done something wrong and it’s out of our control, or that something bad will happen in future and it’s (again) out of our control.

Research has shown how closely our worries about control can be linked to mental health issues. In one Scottish national survey, among people reporting ‘complete control’ over their lives, 14% had mental health issues. But among those reporting ‘little control’, the figure was 56%.Brauholtz, S., Davidson. S., King, S. (2004) ‘Well? What do you think? The second national Scottish survey of public attitudes to mental health, mental well-being and mental health problems’. [online] Edinburgh: Scottish Executive. Available at: [accessed 17 Aug. 2017].

Positive expectations, thoughts, and beliefs

It may seem counterintuitive, but stress can also be caused by positive expectations, thoughts, and beliefs.

For instance, we might be too excited about the future, too stimulated from socialising, too happy about a new relationship, and so on. This can release too much cortisol, and disrupt our HPA axis.

Chronic positive stress can have detrimental effects on our hormonal balance. It can contribute to insomnia and anxiety, and eventually lead to mental health issues such as depression.

How thoughts and beliefs can impact our mental health.

Mental health effects of stress


In 2007, a study by the American Psychological Association estimated that 75% of all visits to the doctor are stress-related.

Stress can have a range of effects on our mental health. For instance, it can lead to:

Below are some of the ways that stress can make our mental health issues worse.

Chronically high levels of stress hormones can contribute to the dysregulation of our immune system. This can lead to inflammation:Kharrazian, D. (2013). Why Isn’t My Brain Working? Carlsbad, CA: Elephant Press, p.90.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.125, p.109

  • Stress hormones suppress our immune system, so that it can focus on essential functions such as pumping blood and sugar to our muscles
  • High levels of cortisol can lead to increased numbers of inflammatory cytokines, and reduced numbers/activity of T cells and NK cells, which help our immune system to monitor cancer cells
  • Chronically high levels of cortisol may affect our healthy brain function, and degrade the blood-brain barrier, which protects our brain from infectious agents
  • The suppression of our immune system can also lead to an increase in infections and gastrointestinal issues, both of which can be detrimental to mental health

How Inflammation can impact our mental health.

Chronically high levels of stress can inhibit the synthesis of prostaglandins.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.122.

These are compounds found in our bodily tissues. They help speed up the blood flow through those tissues, and so they’re essential for helping our bodies heal naturally.

Without healthy tissues, we may feel more tired or low on energy, and become prone to symptoms of depression.

Chronically high stress levels can cause a range of digestive and nutritional issues.

All of the issues below can directly or indirectly have negative effects on our mental health.

Digestion and nutrient absorption

Chronic stress can hamper digestion, and reduce the absorption of nutrients that are key for our mental health:Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.120.Behrendt, I., Schneider, I., Schuchardt, J. P., Bitterlich, N., Hahn, A. (2016). ‘Effect of an herbal extract of Sideritis scardica and B-vitamins on cognitive performance under stress: a pilot study’. International Journal of Phytomedicine, [online] 8(1), pp. 95–103. Available at: [accessed 30 Aug. 2017].Gottfried, S. (2013). The Hormone Cure. New York, NY: Scribner, p.100.

  • High cortisol levels tell our digestion to slow down, in favour of more important bodily functions involved in the ‘fight or flight’ response
  • Blood is diverted from our stomach to our muscles
  • The production of digestive enzymes and saliva is reduced
  • Our intestinal contractions and our absorption of nutrients are reduced
  • Chronic stress can deplete our stocks of tyrosine and magnesium
  • Chronic stress can also deplete our stocks of vitamins B1, B5, B6, and B12; these are important for our stress tolerance, because they’re involved in the synthesis of hormones and neurotransmitters, including adrenaline, noradrenaline, and serotonin

Gut inflammation and IBD

Chronic stress can contribute to gut inflammation, and in particular IBD (irritable bowel disease).Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.122.

IBD can cause a number of symptoms, including:

  • Bloating
  • Diarrhoea
  • Constipation
  • Abdominal pain (due to inflammation)

Gut dysbiosis

Chronic stress can cause gut dysbiosis. High stress levels can affect the balance of healthy and harmful bacteria in our gut.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.108.

Intestinal permeability

Chronic stress can contribute to gut leakiness, or intestinal permeability. This affects the healthy development of the intestinal barrier, and affects our absorption of nutrients.Vanuytsel, T., van Wanrooy, S., Vanheel, H., Vanormelingen, C., Verschueren, S., Houben, E., Salim Rasoel, S., Tόth, J., Holvoet, L., Farré, R., Van Oudenhove, L., Boeckxstaens, G., Verbeke, K., Tack, J. (2014). ‘Psychological stress and corticotropin-releasing hormone increase intestinal permeability in humans by a mast cell-dependent mechanism’. Gut, [online] 63(8), pp. 12931299. Available at: [accessed 1 Sept. 2017].

How nutritional imbalances can impact our mental health.

How gut issues can impact our mental health.

Chronic stress can result in a number of changes to our hormonal balance.

These changes have been closely linked to a number of mental health issues:Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.3, p.48, p.125.Smith, S., Vale, W. (2006). ‘The role of the hypothalamic-pituitary-adrenal axis in neuroendocrine responses to stress’. Dialogues in Clinical Neuroscience, [online] 8(4), pp. 383–395. Available at: [accessed 30 Aug. 2017].

  • High levels of cortisol can suppress our thyroid metabolism, affecting our levels of T3, which controls our temperature, metabolism, and heart rate
  • High cortisol levels can also reduce our sex hormone levels
    • In men, low levels of testosterone can lead to fatigue, low mood, and loss of libido
    • In women, low levels of estrogen, progesterone, and testosterone can lead to anxiety, insomnia, and depression
  • Chronic stress can cause a dysregulation of the HPA axis, leading to cognitive issues, attention issues, insomnia, anxiety, and depression

How hormonal imbalances can impact our mental health.

Chronic stress, and high levels of cortisol, can reduce the levels of several key neurotransmitters, such as epinephrine, norepinephrine, and dopamine.

These reductions have been linked to apathy, attention issues, and symptoms of depression.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.204.

How neurotransmitter imbalances can impact our mental health.

According to the American Psychological Association, 44% of people with ‘unhealthy amounts of stress’ suffer sleep issues of some kind.Gottfried, S. (2013). The Hormone Cure. New York, NY: Scribner, p.76.

Sleep is when our bodies rest and repair themselves, so not being able to sleep deeply or for long enough can prevent this from happening.

Getting fewer than seven hours of sleep per night, or losing an hour of our usual sleeping time, can also increase our cortisol levels, which can lead to (or make worse) symptoms of anxiety.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.34, p.96, p.143.

How poor sleep can impact our mental health.

High cortisol levels can be toxic in high amounts, and our brains are vulnerable to toxins.

Excess cortisol, as a result of stress, has been linked with several cognitive issues:Amen, D. (2012). Use Your Brain to Change your Age. London: Hachette, p.127.Gottfried, S. (2013). The Hormone Cure. New York, NY: Scribner, pp.86–87.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.117.Gottfried, S. (2013). The Hormone Cure. New York, NY: Scribner, p.63.

  • High cortisol levels have been linked with impaired memory, dementia, and Alzheimer’s disease
  • They have also been shown to alter the arrangement of our neurons, and even to destroy brain cells entirely (neurodegeneration)
  • The prolonged exposure of brain cells to cortisol can reduce their ability to take up glucose, and cause them to shrink
  • BDNF, a brain chemical which is essential for the growth of nerve cells, is reduced by cortisol; this can affect our learning, thinking, and long-term memory

The effects of stress on our brains can be rapid. Just two weeks of high cortisol levels can shrivel our dendrites (the connections between brain cells). The good news, though, is that once our cortisol levels decrease again, our dendrites can grow back.Holford, P. (2004). Patrick Holford’s New Optimum Nutrition Bible. London: Piatkus, p.85.

Read more about cognitive decline:

Chronically high levels of cortisol, caused by stress, have been linked to anxiety, panic, and obsessive-compulsive disorder (OCD).Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.114.

High stress and cortisol levels can also affect the regularity of our heart rate, which is often another key factor in anxiety.McCraty, R., Zayras, M.A. (2014) ‘Cardiac coherence, self-regulation, autonomic stability, and psychosocial well-being’. Frontiers in Psychology, [online] 5, p.1090. Available at: [accessed 1 Sept. 2017].

Read more about anxiety.

There’s a well-established correlation between high levels of cortisol and symptoms of depression.Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.34, p.67, p.109, p.116, p.118

  • Depressed people frequently show high levels of cortisol
  • Drugs that shut off the production of cortisol have been shown to reduce symptoms of depression
  • Some people given synthetic cortisol (to treat autoimmune conditions) have developed memory problems and depressive symptoms

Research is ongoing, and it’s beginning to look like there’s also a causal link between stress and depression:Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.116, p.118.

  • In one study, 90% of depressive episodes were shown to be caused by stressful life events
  • A number of studies on rats exposed them to repeated stresses, and showed that their brains became resistant to specific pleasure pathways; in other words, like depressed people, they needed higher levels of dopamine, serotonin, and endorphins to achieve any pleasure

On the strength of these links between stress and depression, many drug companies are currently researching anti-depressants that would target cortisol. (At the moment, the most popular antidepressants target serotonin.)Talbott, S. (2007). The Cortisol Connection. Alameda, CA: Hunter House, p.24.

Read more about depression.