In prehistoric times, the physical changes in response to stress were an essential adaptation for meeting natural threats. Even in the modern world, the stress response can be an asset for raising levels of performance during critical events, such as a sports activity, an important meeting, or in situations of actual danger or crisis.
If stress becomes persistent and low-level, however, all parts of the body's stress apparatus (the brain, heart, lungs, blood vessels, and muscles) become chronically over-activated or under-activated. Such chronic stress may produce physical or psychological damage over time. Acute stress can also be harmful in certain situations, particularly in individuals with preexisting heart conditions.
Studies suggest that the inability to adapt to stress is associated with the onset of depression or anxiety.
Some evidence suggests that repeated release of stress hormones produces hyperactivity in the hypothalamic-pituitary-adrenal (HPA) system, and disrupts normal levels of serotonin, the brain chemical that is critical for feelings of well-being. Some people appear to be more at risk for an overactive HPA system under stress, including those with the personality traits that cause perfectionism. Certainly, on a more obvious level, stress reduces the quality of life by reducing feelings of pleasure and accomplishment. In addition, relationships are often threatened in times of stress.
The full impact of mental stress on heart disease is just coming to light, but the underlying mechanisms are not always clear. Stress can certainly influence the activity of the heart when it activates the automatic part of the nervous system that affects many organs, including the heart. Such actions and others could theoretically affect the heart badly in several ways:
Evidence is still needed to confirm any clear-cut relationship between stress and heart disease
Evidence links stress to heart disease in men, particularly in work situations where they lack control. The association between stress and heart problems in women is weaker, and there is some evidence that the ways women cope with stress may be more heart-protective.
A condition called stress cardiomyopathy (or Takotsubo cardiomyopathy) is widely recognized. In this disease, intense emotional or physical stress causes severe but reversible heart dysfunction. The patient experiences chest pain, and EKGs and echocardiograms indicate a heart attack, but further tests show no underlying obstructive coronary artery disease.
Psychological stress is also recognized as a possible cause of acute coronary syndrome (ACS), a collection of symptoms that signify heart attack or approaching heart attack. In one study of men who suffered ACS at work or up to 2 hours after work, many of the men were found to have anger and negative emotions. A review of studies on blood qualities found that high levels of psychological stress are associated with harmful changes to the blood. The research suggests that stress has the potential to trigger ACS, particularly in patients with heart disease. The studies also suggest that the risk is greatest immediately after the stressful incident, rather than during it.
Stress Reduction and Heart Disease. Studies suggest that treatments that reduce psychological distress improve long-term outlook in people with heart disease, including after a heart attack. Evidence indicates that stress management programs may significantly reduce the risk of heart attacks in people with heart disease. Specific stress management techniques may help some problems but not others. For example, acupuncture in one study helped people with heart failure but had no effect on blood pressure. Relaxation methods, on the other hand, may help people with high blood pressure.
In some people, prolonged or frequent mental stress causes an exaggerated increase in blood pressure, a risk factor for stroke.
Chronic stress affects the immune system in complicated ways, and may have various results.
Susceptibility to Infections. Chronic stress may have an effect on the immune system's response to infections.. Several studies claim that people under chronic stress have low white blood cell counts and are vulnerable to colds. Once a person catches a cold or flu, stress can make symptoms worse. People who carry the herpes virus be more susceptible to viral activation following exposure to stress.
Inflammatory Response. Some evidence suggests that chronic stress triggers an over-production of certain immune factors called cytokines. Such findings may partly explain the association between chronic stress and numerous diseases, including heart disease and asthma.
A relationship between more stress and cancer has not been proven. Although stress reduction techniques have no effect on survival rates, studies show that they are very helpful in improving a cancer patient's quality of life.
The brain and intestines are strongly related, and are controlled by many of the same hormones and parts of the nervous system. Indeed, some research suggests that the gut itself has features of a primitive brain. It is not surprising then that prolonged stress can disrupt the digestive system, irritating the large intestine and causing diarrhea, constipation, cramping, and bloating. Excessive production of digestive acids in the stomach may cause a painful burning.
Irritable Bowel Syndrome. Irritable bowel syndrome (or spastic colon) is strongly related to stress. With this condition, the large intestine becomes irritated, and its muscular contractions are spastic rather than smooth and wave-like. The abdomen is bloated, and the patient experiences cramping and alternating periods of constipation and diarrhea. Sleep disturbances due to stress can make irritable bowel syndrome even worse.
Peptic Ulcers. It is now well-established that most peptic ulcers are either caused by the H. pylori bacteria or the use of nonsteroidal anti-inflammatory (NSAID) medications (such as aspirin and ibuprofen). Nevertheless, studies still suggest that stress may predispose someone with H. pylori to ulcers.
Inflammatory Bowel Disease. Although stress is not a cause of inflammatory bowel disease (Crohn's disease or ulcerative colitis), there are reports of an association between stress and symptom flare-ups.
Stress can have varying effects on eating problems and weight.
Weight Gain. Often stress is related to weight gain and obesity. Many people develop cravings for salt, fat, and sugar to counteract tension. As a result, they gain weight. Weight gain can occur even with a healthy diet, however, in some people exposed to stress. In addition, the weight gained is often abdominal fat, a predictor of diabetes and heart problems.
The release of cortisol, a major stress hormone, appears to encourage abdominal fat and may be the primary connection between stress and weight gain. Cortisol is a glucocorticoid. These hormones, along with insulin, appear to be responsible for stress-related food cravings. Evidence suggets that hormonally induced cravings for "comfort foods" may have a biological benefit for managing stress. Eating comfort foods appears to reduce the negative hormonal and behavioral changes associated with stress, which might lessen the impact of stress on an individual. Carbohydrates in particular may increase levels of tryptophan and large neutral amino acids. This leads to more serotonin, which might improve mood and performance under stress.
There may be a "reward-based stress eating" model. In this theory, stress and tasty, high-calorie foods cause the brain to make chemicals called endogenous opioids. These neurotransmitters help protect against the harmful effects of stress by slowing activity of a brain process called the hypothalamic-pituitary-adrenal (HPA) axis, thus weakening the stress response. Repeated stimulation of the reward pathways through stress-induced HPA stimulation, eating tasty food, or both, may lead to changes in the brain that cause compulsive overeating.
Eating Disorders. Chronically elevated levels of stress chemicals have been observed in patients with anorexia and bulimia. Some studies, however, have not found any strong link between stress and eating disorders. More work is needed to determine if changes in stress hormones are a cause or result of eating disorders.
Stress can exacerbate existing diabetes by impairing the patient's ability to manage the disease effectively.
Researchers are attempting to find the relationship between pain and emotion, but the area is complicated by many factors, including effects of personality types, fear of pain, and stress itself. A recent study suggests that chronic pain may impair the action of neutrophils, thereby weakening the immune response.
Muscular and Joint Pain. Stress may intensify chronic pain caused by arthritis and other conditions. Psychological distress also plays a significant role in the severity of back pain. Some studies have clearly associated job dissatisfaction and depression to back problems, although it is still unclear if stress is a direct cause of the back pain.
Headaches. Tension-type headaches are highly associated with stress and stressful events. Sometimes the headache does not start until long after the stressful event has ended. Additionally, stress can contribute to the development of headaches or cause headaches to occur more often.
Some research suggests that people who suffer from tension-type headaches may have some biological predisposition for translating stress into muscle contractions. Among the wide range of possible migraine triggers is emotional stress (although the headaches often erupt after the stress has eased).
The tensions of unresolved stress frequently cause insomnia, generally keeping the stressed person awake or causing awakening in the middle of the night or early morning. This appears to be due to the fact that stress causes physiological arousal during non-rapid eye movement sleep.
Sexual Function. Stress can lead to diminished sexual desire and an inability to achieve orgasm in women. Stress response causes androgen levels to drop, causing temporary erectile dysfunction in men.
Premenstrual Syndrome. Some studies indicate that the stress response in women with premenstrual syndrome may be more intense than in those without the syndrome.
Fertility. Chronic stress may even affect fertility. Stress hormones have an impact on the hypothalamus gland, which produces reproductive hormones. This effect may lead to changes in a woman's menstrual cycle, with a possible effect on fertility.
Effects on Pregnancy. Old wives' tales about a pregnant woman's emotions affecting her baby may have some credence. Stress may cause physiological alterations, such as increased adrenal hormone levels or resistance in the arteries, which may interfere with normal blood flow to the placenta. Maternal stress during pregnancy has been linked to a higher risk for miscarriage, lower birth weights, and increased incidence of premature births. Some evidence also suggests that stress experienced by expectant mothers can even influence the way in which the baby's brain and nervous system will react to stressful events. Indeed, one study found a higher rate of crying and low attention in infants of mothers who had been stressed during pregnancy.
Menopause. A drop in estrogen levels during perimenopause and menopause may be responsible for changes in mood precipitated by stress.
Stress affects the brain, particularly memory, but the effects vary widely depending on whether the stress is acute or chronic.
Effect of Acute Stress on Memory and Concentration. Studies indicate that the immediate effect of acute stress impairs short-term memory, particularly verbal memory. On the plus side, high levels of stress hormone during short-term stress have been associated with enhanced memory storage and greater concentration on immediate events. The difference in effect may be due to how cortisol impacts glucocorticoid receptors in the hippocampus and prefrontal cortex.
Effect of Chronic Stress on Memory. If stress becomes chronic, sufferers often experience loss of concentration at work and home, and they may become inefficient and accident-prone. In children, the physiologic responses to chronic stress can clearly inhibit learning. Studies have connected long-term exposure to excess amounts of cortisol (a major stress hormone) to shrinking of the hippocampus, the brain's memory center. For example, two studies reported that groups who suffered from post-traumatic stress disorder (Vietnam veterans and women who suffered from sexual abuse) displayed up to 8% shrinking of the hippocampus. It is not yet known if this shrinking is reversible.
Skin Disorders. Stress plays a role in worsening numerous skin conditions, including hives, psoriasis, acne, rosacea, and eczema, and is one of the most common causes of eczema. Unexplained itching may also be caused by stress. Evidence suggests that experiencing the stress of a traumatic event (parental divorce or separation, or a severe disease in a family member) before age 2 increases the risk of developing eczema.
Unexplained Hair Loss (Alopecia Areata). Alopecia areata is hair loss that occurs in localized (individual) patches. The cause is unknown, but stress is suspected as a player in this condition. For example, hair loss often occurs during periods of intense stress, such as mourning.
Teeth and Gums. Stress has now been implicated in increasing the risk for periodontal disease, a gum disease can cause tooth loss.
People under chronic stress often turn to alcohol abuse or tobacco use for relief. The damage these self-destructive habits cause under ordinary circumstances is compounded by the physiological effects of stress itself. Many people also resort to abnormal eating patterns or passive activities, such as watching television. The results of one national survey show that: "Americans engage in unhealthy behaviors such as comfort eating, poor diet choices, smoking and inactivity to help deal with stress."
Alcohol affects receptors in the brain that reduce stress. Lack of nicotine increases stress in smokers, which creates a cycle of dependency on smoking.
The cycle is self-perpetuating: a sedentary routine, an unhealthy diet, alcohol abuse, and smoking all promote heart disease. They also interfere with sleep patterns, and lead to increased rather than reduced tension levels. Drinking four or five cups of coffee, for example, can cause changes in blood pressure and stress hormone levels similar to those produced by chronic stress. Animal fats, simple sugars, and salt are known contributors to health problems.
Dallman MF, Pecoraro NC, la Fleur SE. Chronic stress and comfort foods: self-medication and abdominal obesity. Brain Behav Immun. 2005;19:275-280.
Field T, Hernandez-Reif M, Diego M, et al. Cortisol decreases and serotonin and dopamine increase following massage therapy. Int J Neurosci. 2005;115:1397-1413.
Ginsburg KR and the Committee on Communications and Committee on Psychosocial Aspects of Child and Family Health. Clinical Report: The Importance of Play in Promoting Healthy Child Development and Maintaining Strong Parent-ChildBonds. Last accessed on 17 October, 2006.
Hammerfald K, Grau M, et al. Persistent effects of cognitive-behavioral stress management on cortisol responses to acute stress in healthy subjects-A randomized controlled trial. Psychoneuroendocrinology. 2005 Sep 22; epub ahead of print.
Kreitzer MJ, Gross CR, Ye X, et al. Longitudinal impact of mindfulness meditation on illness burden in solid-organ transplant recipients. Prog Transplant. 2005;15:166-172.
Larzelere MM, Jones GN. Stress and Health. Primary Care: Clinics in Office Practice. 2008;35(4):839-856.
Wang J. Work stress as a risk factor for major depressive episode(s). Psychol Med. 2005;35:865-871.
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