Studies estimate that 75-90% of visits to primary care physicians are for disorders caused by or linked to stress. While the workplace is the most common source of stress for American adults (up to 40% say their job is very or extremely stressful), causes of chronic stress abound for adults, adolescents and children, and can include major life changes, financial problems, demands of family or children, and issues like violence and threats to personal safety, environmental pressures leading to substance abuse or other unhealthy lifestyle habits, and social isolation or loneliness.
You’ve likely experienced the effects of stress on your health first-hand–perhaps you’ve gotten a cold easier when working against a difficult deadline at work, or craved sugary, carbohydrate-rich foods at the end of a stressful day. These subtle signs of an unhealthful stress response may not have been enough to have prompted you to change in the habits, decisions and relationships which contribute to your stress. You should know that the harmful effects of chronic stress are real, and they have been shown to lead to diseases such as obesity, diabetes, autoimmune disorders, depression, substance abuse, and cardiovascular disease.
How stress works
Chronic stress disrupts the homeostatic relationship between the hypothalamus, pituitary gland and adrenal glands, often referred to as the HPA Axis, and excites the sympathetic nervous system (SNS). A stressful experience triggers the release of cortisol by the HPA axis and epinephrine/nor-epinephrine (aka, adrenaline/noradrenaline) by the SNS, which initiates a cascade response within the body.
The function of this stress response is to prepare the body for “fight or flight” by mobilizing stored energy, directing blood flow to major muscle groups in the arms and legs and sensitizing tissues to hormones and neurotransmitters, enabling us to respond quickly and effectively when faced with a threatening situation.
Cortisol helps to produce an excitatory state by increasing heart rate, blood pressure and blood glucose levels, and increasing the sensitivity of body tissues to hormones and neurotransmitters, ensuring that the muscles have plenty of oxygen and energy and respond immediately.
Epinephrine and norepinephrine increase heart rate and also increase blood viscosity to promote clotting in case of injury.
The side-effects of chronic stress
Over time, increased blood pressure, heart rate and clotting can fatigue the heart, potentially leading to heart disease.
Chronically increased blood glucose levels can lead to tissue damage throughout the body and precipitates diabetes.
Decreased insulin levels can lead to increased hunger, fat storage and weight gain.
In small amounts cortisol increases anti-inflammatory activity to speed recovery, but when elevated, it weakens the immune system and decreases anti-inflammatory activity to prevent the body from overreacting to foreign bodies or disease when resources need to be reserved for reacting to the stressor.
In order to suppress the immune system, cortisol activates the increased production of tryptophan pyrrolase, the enzyme which initiates the irreversible breakdown of tryptophan. Tryptophan is required by the body for the manufacture of both serotonin and melatonin—when stores are depleted, both serotonin and melatonin levels plummet. Reduced levels of these neurotransmitters have been linked to many symptoms of depression.
Chronic overstimulation of the HPA axis and the disruption of hormones and neurotransmitters within the body can lead to dysfunction in any or all of the systems involved. For instance, the adrenal glands may be fatigued by continuous stimulation during periods of physical or emotional stress, and in that state are no longer capable of a healthy response. This can lead to exhaustion, poor immune response and depression.
The stress response system exists so that we can respond to immediate stressors, such as predators and other life-threatening situations; once the stressor is removed, HPA axis and SNS activity is reduced and the body returns to homeostasis. However, situations of chronic stress lead to continuous activity of the HPA axis and SNS, which causes systemic imbalance, and ultimately can promote physiological disorders such as diabetes, osteoporosis, heart disease and autoimmune disease and psychological disorders including depression, anxiety, alcoholism and eating disorders.
Find out why many health professionals are recommending yoga to reduce stress and to help alleviate its harmful effects in How Yoga Relieves Stress.
Moffett, John R., and MA Aryan Naboodiri (2003). “Tryptophan and the immune response.” Immunology and Cell Biology, 81, 247-265.
Ross, A., & Thomas, S (2010). “The health benefits of yoga and exercise: A review of comparison studies.” The Journal of Alternative and Complementary Medicine, 16, 3-12.
Walton, Kenneth G., and Debra Levitsky (1995). “A Neuroendocrine Mechanism for the Reduction of Drug Use and Addictions by Transcendental Meditation.” In Self-Recovery: Treating Addictions Using Transcendental Meditation and Maharishi Ayurveda, Vol. I, by David F. O’Connell and Charles N. Alexander, 89-117. Binghamton, NY: Haworth Press, Inc.