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When someone experiences stress, it sets off a series of physiological events in the body that involve the brain, hormones, the immune system, and many other organs. 1 Massive and extended periods of stress can even lead to disease and dysfunction. Below are some examples of how stress can negatively impact human health.


Chronic stress takes a particularly rough toll on the heart and cardiovascular system because it forces the entire system to work harder. To illustrate this point, think of the heart as a mechanical pump and the connected blood vessels as hoses. Together they transport blood throughout the body. But just like parts in a machine, regular and strenuous use will wear them out.

When we experience stress, our bodies respond by releasing hormones (epinephrine or adrenaline, and norepinephrine or noradrenaline) that cause the “fight or flight” response. These hormones prime our bodies to deal with an acute threat by increasing blood flow and oxygen to our muscles. Our hearts play an important role in this, beating harder and faster to pump blood around the body.

If we experience ongoing stress, these hormones continue to be released and our bodies must cope with chronically increased blood flow. The development of hypertension, which is chronic high blood pressure, is linked to unresolved stress. To deal with the increased blood flow triggered by the stress response, blood vessels begin to thicken and consequently become more rigid. These rigid, thickened blood vessels are unable to stretch to accommodate the elevated force of blood flow. As blood vessels become stiffer, blood pressure increases, just as the pressure of water from a hose increases if you place your thumb over the end to force more water through a smaller opening. A nasty cycle soon manifests because this resistance often increases blood pressure and causes even more stiffening of the blood vessels, which further increases blood pressure, and so on.

In response to chronically high blood pressure, the left part of the heart must pump harder to push blood through stiffened, high pressure vessels. Consequently, the heart will also thicken with muscle. This reaction is known as left ventricular hypertrophy, which raises the likelihood of developing an irregular heartbeat and significantly is regarded as one of the best predictors for developing heart disease.

Constant stress is also linked to atherosclerosis, a condition in which blood vessels around the heart become clogged and blood flow decreases. Additionally, “bad” cholesterol, also called low-density lipoprotein associated cholesterol (LDL), increases during stress in response to some of the hormones released in the “fight or flight” response. This type of cholesterol contributes to the materials that block blood vessels.

All these factors related to chronic stress increase the risk of acquiring heart disease, which may culminate in a heart attack. Unfortunately, a person with a damaged cardiovascular system is even more sensitive to stressors than someone in better health. 2 3


The effects of the stress response on blood vessels increases the risk of stroke. The constantly increased blood flow through vessels increase the risk of damage to vessel walls. This can cause a blood vessel to burst, or to become thickened and blocked. When a blood vessel in the brain becomes blocked or bursts, the lack of blood flow results in the sudden loss of brain function and can cause permanent damage. ,4 In some people, rather than one larger vessel, multiple smaller vessels may become blocked. When this occurs, small areas throughout the brain may slowly lose blood flow, with these scattered areas of damage manifesting as dementia. 2 4


Few people will likely be shocked to learn that stress can affect both the quality and quantity of someone’s sleep. In fact, approximately 75 per cent of insomnia cases are brought on by a major stressor. 2

However, getting a good night’s sleep is also important for warding off stress. This is because sleep is the main time when the stress response is shut off, meaning the body experiences a drop in the amount of stress hormones circulating. So if a person constantly trades quality sleep in favour of another activity, he or she will be more susceptible to worry and anxiety. 2


Type 1 (juvenile) Diabetes

For suffers of Type 1 diabetes, the immune system destroys cells in the pancreas that produce the hormone insulin. As a result of low insulin levels, cells starve because they have a very limited capacity to store glucose and fatty acids. Without fuel, organs can’t function properly. Instead, excess glucose and fatty acids circulate in the bloodstream, which can lead to clogged blood vessels and the development of cataracts.

Managing stress is crucial for people with Type 1 diabetes because stress aggravates the condition and damage to blood vessels. 2 3

Type 2 (adult-onset) Diabetes

Type 2 diabetes, which is associated with age-related weight gain, is not caused by a lack of insulin, but by the inability of cells to respond to the hormone. Significantly, insulin tells the body to transform fat, sugar and proteins in the bloodstream into fat and protein. But when too much fat is stored away, cells become full and less responsive to insulin, meaning excessive amounts of glucose and fatty acids begin circulating in the body.

To make matters worse, the stress response pushes even more glucose and fatty acids into the bloodstream, which causes further resistance to insulin and its production. Increased insulin resistance can worsen diabetes, and increase the amount of medication required to manage it. Diabetics are at increased risk of atherosclerosis, where blood vessels become damaged and clogged, because of the effects of increased circulating glucose and fatty acids on blood vessel walls. 2 3


Short-term stress causes the digestive system to shutdown, while chronic stress leads to diseases of the digestive system and can also increase the severity of existing gastrointestinal issues such as colitis.

Studies also demonstrate that people experiencing extreme stress, depression, or anxiety are more likely to develop ulcers in the small intestine. 2 3


Significant amounts of research consistently link ongoing stress with a weakened immune system. This is thought to occur because of cortisol, a stress hormone, which is known to dampen the immune response. One study revealed that people undergoing relationship or work-related conflict for a month or longer were at a particularly high risk of becoming sick when exposed to an infectious agent. 5

Another notable study compared two groups to monitor the activity of immune cells called natural killer (NK) cells, which fight against cancer and infections. The first group consisted of spousal caregivers of people with Alzheimer’s disease and the second was a control group matched by age and health. Results showed the functioning of NK cells in the caregivers was considerably inhibited, including in cases where the spouse had died three years earlier. The immune systems of caregivers with the least amount of social support were the most suppressed. 1

Chronic stress also has an obvious effect on the body’s ability to heal, which may also be due to the ongoing release of cortisol. An additional study of Alzheimer caregivers showed their wounds took about nine days longer to heal than those of people in control groups. 1 Slower wound healing also occurred in married couples experiencing negative or hostile interactions as opposed to couples who engaged in supportive discussions. 5


Stress and depression are strongly linked, and people who are more vulnerable to depression often experience a higher amount of stress. Chronic stress is also linked to anxiety, including uncontrollable worry and severe panic attacks. 2 4


Being constantly stressed out also requires a lot of energy, because the stress response involves moving nutrients in and out of the bloodstream. Consequently, people who experience regular and unresolved stress are more easily worn out and are more likely to suffer from regular fatigue. 2 3 4

Now that you know the effects of stress on you and your body, why not learn how to deal with stress.

Maté, Gabor. When the Body Says No: Understanding the Stress-Disease Connection. New Jersey: John Wiley & Sons, Inc., 2003.
Sapolsky, Robert M. Why Zebras Don’t Get Ulcers. 3rd ed. New York: Holt Paperbacks, 2004.
Mitchell, Tamara, and Sally Longyear, ed. Stress: Part 1 The Physiology of Stress. Working Well Ergonomics Information Website. 6 May 2013. .
Heart & Stroke Foundation. What is a Stroke? Aug. 2009. 6 May 2013. .
Graham, Jennifer, et al. “Stress, Age and Immune Function: Toward a Lifespan Approach.” US National Library of Medicine. 19 May 2006. 6 May 2013.

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Richard Tytus

Written in conjunction with Richard Tytus, MD

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