In today’s fast paced world, stress is generally thought of as experiences that causes anxiety, frustration or fear. Public speaking is a good example. Many people would become very anxious about public speaking. Time pressures, deadlines, conflicts with the boss, financial difficulty and so on, are all examples of stress. However, it doesn’t affect everyone in the same way. It depends on how we perceive events and situations and how we manage them as to how much stress we experience. When we get stressed, our brain orchestrates a complex cascade of chemical reactions that release stress hormones into our systems.
The primary stress hormones are adrenalin, cortisol and norepinephrine. Their role is to make us more aware, focused and mobilized for action. This is called the ‘fight or flight’ response. In prehistoric times, this response was critical because humans had to deal with life or death situations all the time such as dealing with hungry sabre toothed cats! The fight or flight response is still with us today but we no longer have to deal with the threats that our ancestors once did. We have completely different stress triggers, the majority of which are not life threatening.
However, not all stress is bad. There is a positive stress and negative stress. In fact, we need a certain amount of positive stress in our lives to adapt and thrive. Positive stress will motivate us to achieve our goals and overcome adversity. It makes us more focused and energetic. Negative stress stress is caused by too many perceived stressors in our life. Consistent exposure to acute stress and persistent worry and anxiety can lead to chronic stress. So we’ve got positive and negative stress, but this is a bit of a generalization based on how we perceive certain events and circumstances. Within this, there are different types of stress each with its own characteristics, symptoms and duration. Lets take a closer look.
This is the most common type of stress and it is typically short lived. We all know about acute stress as it is part of everyday life. It is caused by those everyday hassles and challenges as well as the anticipated demands and challenges of the near future.
For example, if you’ve got an upcoming deadline on a project, or you preparing for a public speaking presentation or perhaps you’ve got an exam coming up. In these scenarios, acute stress can be good for us in small doses and can keep us motivated, focused and productive. There are also scenarios of acute stress that can be more distressful depending on how we perceive the situation.
For example, getting caught in a traffic jam and being late for a meeting, an interview for a new job, a public speaking engagement or a confrontation with the boss. These are all short term stressors and we can more often than not, handle these without harming our health, if they are not too frequent. You may experience some symptoms in these situations such as irritability, anxiety, tension and headache, back pain, heartburn, acid stomach to name a few. Take for example a public speaking engagement. You might feel anxious about this in the run up to the event and feel very nervous before speaking. You may get sweaty hands, increased heart rate and shortness of breath prior to or even during the event, depending on how you deal with stress. These are signs that your stress hormones are hard at work!
Episodic Acute Stress
When acute stress becomes more frequent, the symptoms increase. People who are always busy, rushing around, overwhelmed with work, with little organisation in their lives are more prone to episodic acute stress. This type of person seems to be always stressed out or worried about something. This isn’t to say that all people who are busy with a high workload are stressed out. We have to make a distinction here. Some people have a capacity for dealing with large workloads and actually thrive on it, taking it all in their stride, rather than feeling stressed. A key factor here is a person’s mindset and how they perceive potentially stressful events and how they manage them.
People who are experiencing episodic acute stress may well be short tempered, irritable, anxious and tense. They can come across as being very impatient and abrupt, experiencing a sense of time urgency. They may worry persistently about things that haven’t happened and be quite pessimistic in their outlook, always seeing the worst outcome. The symptoms of episodic acute stress are persistent headaches, migraines, hypertension and chest pain which can, if not treated, lead to heart disease. This level of stress may require some kind of intervention to get things back to normal. This is not a good place to be in terms of health. People who ignore there symptoms and carry on regardless are on the road to chronic stress and some very poor health outcomes.
Chronic stress occurs in situations where people are exposed to frequent and consistent acute stressors over a prolonged period of time. People with chronic stress may have been enduring incredibly difficult or unhappy times for years, whether that be an unhappy marriage that has lead to a divorce, living with a debilitating disease for many years, working long hours in a high pressure job or working in a job that is soul destroying.
This kind of stress wears away at a person everyday, every week, every month for years taking a huge toll on the body and can ultimately lead to disease of some kind if not treated. In fact, chronic stress has been linked to heart disease, high blood pressure, type II diabetes, obesity, weakened immune system and depression.(1) But the effects of chronic stress are worst for people at risk of developing these conditions in the first place. For instance, if one has a family history of heart disease, diabetes, high blood pressure, or if a person has an unhealthy diet and lifestyle habits, then chronic stress can flip the switch that triggers these health problems. When the stress response is activated, the body goes into fight or flight mode and stress hormones are released into the bloodstream and this drastically affects our body that heart rate increases, blood pressure increases, the immune system is supressed and so.
With chronic stress, the stress response is continual and therefore, the body has elevated levels of stress hormones. The fight or flight response is designed to be short term to get us out of dangerous situations. It is a survival mode. However, when is always on, and stress hormones are continually released into the bloodstream, there are a multitude of negative health consequences. The consequences of chronic stress are serious, particularly as it contributes to anxiety and depression. People who suffer from depression and anxiety are at twice the risk for heart disease than people without these conditions. (2)
The Biology of Stress
In any given situation, we make a judgement and decide whether or not it is stressful. This decision is made based on sensory input and how we process what we see, hear and feel. When someone experiences a stressful event, the amygdala, an area of the brain that contributes to emotional processing, will send a signal to the hypothalamus and the Hypothalamic Pituitary Axis is activated. The hypothalamus which resides at the base of the brain, sends a chemical message to the pituitary gland.
The pituitary gland secretes adrenocorticotropic hormone (ACTH) which stimulates the adrenal glands to produce more of the stress hormones.
The adrenal function works in two phases. First adrenaline is released from the adrenal gland. We all know the feeling of adrenaline that occurs when you are suddenly faced with a stressful situation. The heartbeat speeds up, shortness of breath, you start to sweat and you have a heightened sense of awareness. The hypothalamus has activated the adrenal medulla which is part of the autonomic nervous system. (ANS) The ANS is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These activities are generally performed without conscious control. The adrenal medulla secretes the hormone adrenaline which will increase the heart rate, increase blood pressure and increase sweating as well as suppress the parasympathetic nervous system which results in a decrease of digestion. Essentially, the body prepares for taking massive action.
Norepinephrine is also known as noradrenaline and works in conjunction with adrenaline to mobilize the brain and body for action. The primary role of norepinephrine is arousal and in a stressful situation, you become much more aware, focused and responsive. It is also responsible, along with adrenaline to increase heart rate and blood pressure, This is why can feel your heart pounding in a stressful situation. In addition, it triggers the release of glucose into the bloodstream, increases the blood flow to the muscles and increases your rate of breathing so that have more oxygen and energy to fuel the muscles. The overall effect is is to prepare you physically and mentally to deal with a potentially life threatening situation.
In addition, the hypothalamus also secretes CRH (corticotropin-releasing hormone). CRH kills the appetite in the first few seconds of a stress response. There is no need for digestion in a survival situation and this is what the stress response is designed for. Fight or flight is all about survival. It seems like we are cracking a nut with a sledge-hammer when this mechanism kicks in because of the minor hassles and stressors in our lives when it was designed for survival. It seems that evolution hasn’t caught up with modern society!
After approximately one minute, the adrenal cortex releases cortisol which has a number of functions including releasing stored glucose from the liver for energy. In stressful situations, cortisol sends out a signal to the cells to stop responding to insulin. In this scenario, glucose will be prevented from being stored in the cells. The release of cortisol causes the breakdown of muscle protein, which releases amino acids into the bloodstream. These amino acids are then used by the liver to synthesize glucose for energy, in a process called gluconeogenesis. In addition, cortisol leads to the release of energy from fat cells, for use by the muscles. Taken together, these processes ensure we have a large amount of energy that is immediately avaialble for the fight or flight response. When cortisol is present in adequate, or excess amounts, a negative feedback system operates on the pituitary gland and hypothalamus, which alerts these areas to reduce the output of ACTH and CRH in order to reduce cortisol secretion.
In a stressful situation, the hormone dehydroepiandrosterone (DHEA) is also produced in the adrenal cortex in response to ACTH secretion from the pituitary. DHEA is known as a glucocorticoid antoagonist and a stress-induced increase in DHEA and DHEA-S secretion is thought to play a protective role during stressful situations against the effects of cortisol. DHEA reverses many of the unfavorable effects of excess cortisol, creating subsequent improvement in energy, sleep, and mental clarity. It also accelerates recovery from any kind of acute stress and protects against the neurotoxic effects of cortisol. Chronic exposure to stress leads to a substantial reduction in circulating DHEA. In addition, the body uses DHEA to make androgens and estrogens which are the male and female sex hormones.
The body’s stress response system is self limiting in that once the perceived threat has passed, hormone levels return to normal. As adrenaline, norepinephrine and cortisol levels drop, heart rate and blood pressure return to normal levels and all other systems resume normal activity. If stress isn’t resolved and starts to increase over a longer period of time, it becomes chronic and cortisol levels become elevated.
Stress is part of a daily lives and while there are things we can do to avoid unnecessary stress, we need to think of ways to manage stress more effectively and develop our stress management strategy. Everyone reacts to stress differently and what one person perceives as stressful, another may perceive as quite normal. In the next article in this series, we'll explore the effects of stress on health and performance and look are ways to develop a stress management strategy.
1- Baum, A. & Polsusnzy, D. (1999). "Health Psychology: Mapping Biobehavioral Contributions to Health and Illness." Annual Review of Psychology, Vol. 50, pp. 137-163.
2 - Anderson, N.B. & Anderson, P.E. (2003). Emotional Longevity: what really determines how long you live. New York: Viking.
Sports & fitness nutritionist, researcher and author on a mission to improve the human condition. Focusing on evidence-based and outcome-based nutrition, training, mindset & environment