The science of stress: systems, symptoms, and strategies

Stress is such a simple but loaded word. In our fast paced modern age, it’s a common plight – ask friends or family how they are and at least one of them will probably tell you they’re stressed. Their dog ate a sock and the vet bill was expensive, their son has their A Level exams coming up or they have a big project at work that will determine their next promotion.

Life is full of stressors, some that motivate and inspire us, some less serious and shorter term that are easy to shake off. Others are more serious with longer-term impacts. So what causes stress and what kind of impact can it have on your mental and physical health? Read on to find out more.

Stress and stressors

Stressors are the changes and challenges you face that cause mental and physical responses, these responses are what we call stress.¹

Stressors can be things like:²³

Life events – loss of a family member or friend, moving house or country, marriage, divorce, retirement, having a baby, illness diagnosis.
Social – relationship troubles, discrimination, bullying, peer pressure.
Financial – debt, job loss, unexpected expenses, living in poverty.
Work or school-related – exams, tight deadlines, poor management, high work load.
Environmental – noise, pollution, unsafe housing conditions.
Daily challenges – household chores, commuting, caretaking, chronic illness.

Not all of these stressors feel negative, for example getting married or having a baby. These stressors may challenge you in the moment but may end up an overwhelmingly positive addition to your life.

Stress can be categorised into different types, depending on duration, intensity and response.⁴⁵ There are three main types of stress:

Acute stress – Short term stress resulting from challenging situations or immediate stressors. Your fight or flight response may be activated and you may experience physiological changes such as increased heart rate and pupil dilation.
Episodic acute stress – Takes place when people experience regular episodes of acute stress. The stress can affect certain professions such as first responders, or can be lifestyle-related like a disorganised person under pressure with recurring deadlines. With this kind of stress, a person may not be able to return to a resting, relaxed state. It may also worsen health issues and impair daily functioning, with feelings of always being under pressure or in crisis.
Chronic stress – Occurs when the stress carries on for a long term duration like weeks, months or years. This can be caused by long term stressors such as ongoing financial problems or relationship troubles. This can deplete psychological resources and increase risk of a range of diseases and have significant negative health implications.

There are also other types of stress:

Traumatic stress – Appears as a response to a traumatic situation such as a natural disaster or a violent event. Post-traumatic Stress Disorder (PTSD) may result from exposure to this kind of stress and lead to symptoms such as intrusive memories or avoidance behaviours.
Environmental stress – Results from environmental factors such as noise, pollution or unsafe living conditions.
Psychological stress – Arises from cognitive or emotional factors such as worries or negative thoughts. It can manifest states like anxiety or perfectionism.
Physiological stress – A response to internal or external stressors that disrupt homeostasis in the body. This may happen as a result of illness, injury, exposure to toxins or nutritional deficiencies.

Your stress response

Sympathetic nervous system (fight or flight)

Your sympathetic nervous system is responsible for responding to stressors. You may have heard of the fight or flight response, this is the sympathetic nervous system preparing your body to fight the stressor or run away from it! In addition to fight or flight, you may experience a freeze, fawn or flop response when facing stress.⁶

When your sympathetic nervous system is activated the following physiological responses may take place:⁷

Digestion slows
Heart rate increases
Blood vessels constrict increasing blood pressure
Adrenaline is released
Energy stores in the liver are activated for quick energy use
Pupils become enlarged to let more light in

These responses prepare you to face the stressor – whatever it may be. Even if there is no actual threat, such as hearing noises in the night that sound like a burglar but are really just the cat… your brain has perceived there is a threat and your fight or flight response may be activated as a result. This is important to remember as perception of the stressor can mediate fight or flight responses, not just the physical situation.⁸

The SAM axis

The Sympathetic-Adreno-Medullar system (SAM axis) is responsible for the fast physiological stress response. The quick response triggered by SAM activation increases the secretion of the hormones norepinephrine (noradrenaline) and epinephrine (adrenaline).

These bind to receptors that activate cell responses, including an increase in blood pressure, cardiac output, heart rate, sodium retention and oxygen consumption. The SAM axis also activates behaviour changes such as enhanced arousal, alertness, cognition, vigilance and focus.⁹

The HPA axis

The Hypothalamus-Pituitary-Adrenal system (HPA axis) is responsible for the slower physiologically stress response. To put it in basic terms, the activation of the HPA axis releases corticotropin-releasing hormone (CRH) which stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH) into the bloodstream.

The ACTH then stimulates the adrenal cortex to secrete glucocorticoid hormones, like cortisol.¹⁰ Cortisol can then trigger the release of glucose (sugar) from the liver to provide energy.¹¹

What impact can stress have on your health?

Stress has a widespread impact on your body, from affecting your cardiovascular and respiratory systems to your gastrointestinal and reproductive systems. Chronic stress generates ongoing activation of the sympathetic nervous system and HPA axis, driving increased levels of stress hormones like cortisol.

The risks and impacts of chronic stress include:¹²¹³¹⁴

Cardiovascular – Development of atherosclerosis driven by higher oxidative stress, inflammation and endothelial dysfunction and increased likelihood of high blood pressure and heart attack. Alterations in lipid metabolism contributing to dyslipidaemia.
Immune system – Compromised immune response leading to susceptibility to acute infections. Contribution to the development of autoimmune diseases and chronic inflammatory conditions.
Respiratory – Airway inflammation and higher mucus production. Exacerbation of conditions such as asthma and chronic obstructive pulmonary disease (COPD).
Gastrointestinal – Increased gut permeability and inflammation. Development of ulcers and irritable bowel syndrome.
Musculoskeletal – Tension resulting in headaches and worsening of temporomandibular joint disorders. Development of fibromyalgia and low back pain.
Reproductive – Disruption of hormones leading to impaired ovarian function in women and reduced testosterone in men. Advancement of polycystic ovarian syndrome (PCOS) and male hypogonadism.
Psychological – Onset of anxiety and depression, difficulty with memory and focusing and increased irritability.
Sleep disturbances – Development of insomnia or problems with sleeping too much. Can lead to nightmares and sleep disorders.

The risks and effects of chronic stress.

Stress affects us differently

There is no universal way that people respond to stress which also unfortunately means there’s no universal way to decrease your stress response or de-stress! The threshold for sympathetic activation (fight or flight) for the same types of stressors differ depending on the person – their personality, genetics, experiences, coping strategies and support all play a role.

For example, two people may experience ongoing bullying at work in very different ways, both physiologically and emotionally, with one entering a long-term chronic sympathetic activation, unable to move back into a state of rest even after they leave the job. It may impact their confidence and future workplace experiences moving forward. Another person may experience episodic acute stress that resolves once the job has been left and bounces back with confidence.

Genetics

Genetics play a role in how your body responds to stress, some people have variations in their genetics that make them more sensitive to sympathetic activation and activation of the HPA axis predisposing them to stress-induced disorders.¹⁵ Genetics can also play a role in how you perceive and cope with stressors, leading some people to be more or less resilient to stress-related health and mental health problems such as addiction.¹⁶

Life experiences

Experiences faced as children or adults may shape stress responses. Children who experience Adverse Childhood Experiences (ACES) such as living in a home where a parent is violent, abusive or has an addiction or who’s parents have divorced – without the buffer of a stable home and safe, loving caregiver – can experience a long lasting stress response. For some, this can lead to long-term disruptions to their brain development and in their immune, hormone and metabolic systems.¹⁷¹⁸

Other life experiences such as onset of PTSD after a traumatic experience, may also impact future stress responses. However, you don’t need to have experienced something truly horrible for your experiences to influence the way that your body and your mind react to stress.¹⁹

Coping strategies and support

Research shows that having social support can help people cope with stress and lower their sympathetic activation after the stressful event.²⁰ Having a caring partner, friends, family or even a supportive boss or teacher can help people build resilience and cope with stress better than those who don’t have supportive social networks.²¹

Having support can change how a person perceives the stress, with research showing that it can actually change how stressful a person thinks an event or situation is.²² Having a strong social network can also increase psychological flexibility, reducing the likelihood of people using avoidant or maladaptive coping strategies to manage stress and instead engage in more positive and direct coping strategies.²³

Differences in coping strategies from stress can be rooted in personality differences and life experiences. Some people may engage in coping mechanisms such as exercise, getting adequate rest and nutrition and leaning on professionals for support to help them cope. Others may use more harmful strategies to help them cope with stress such as avoidance, not eating or excessive drug and alcohol use.²⁴

Stressors, stress types, factors affecting the stress response, and your stress response (diagram).

Stressors can be small things such as getting constantly stuck in traffic, running late, exams, sports games or larger and longer term things such as the death of a loved one, getting married, dealing with workplace bullying, debt and illness. If you’ve lived most of your life in a state of chronic sympathetic activation, you may not truly realise just how stressed you are! Finding ways to lower your stress response can have a wide range of long term health benefits, including for your gut health.

To help with coping strategies, check out our article Calm the chaos: 9 tips for coping with stress.

Any questions? Contact one of our Nutritional Therapists via live chat, weekdays from 8am to 8pm.