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 where there is actual danger or a 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 pre-existing heart conditions.
Psychological Effects of Stress
Studies suggest that the inability to adapt to stress is associated with the onset of depression or anxiety.
Some evidence suggests that the 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 personality traits that cause perfectionism. On a more obvious level, stress reduces quality of life by affecting 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 influence the activity of the heart when it activates the automatic nervous system. Such actions and others could negatively affect the heart in several ways:
- Sudden stress increases the pumping action and rate of the heart, while at the same time causing the arteries to constrict (narrow). As a result blood pressure rises.
- The emotional effects of stress alter the heart rhythms, which could pose a risk for serious arrhythmias (rhythm abnormalities) in people with existing heart rhythm disturbances.
- Stress causes certain blood cells to become stickier (possibly in preparation for potential injury).
- Stress appears to impair the clearance of fat molecules in the body.
- Stress that leads to depression appears to be associated with increased intima-medial thickness, a measure of the arteries that signifies worsening blood vessel disease.
- Stress causes the body to release inflammatory markers into the bloodstream. These markers may worsen heart disease or increase the risk of a heart attack or stroke.
- Studies have reported an association between stress and high blood pressure, which may be more pronounced in men than in women. According to some evidence, people who regularly experience sudden spikes in blood pressure (caused by mental stress) may, over time, develop injuries to the inner lining of their blood vessels.
Evidence is still needed to confirm any clear-cut relationship between stress and heart disease. However, research has linked 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 in which women cope with stress may be more heart-protective.
Studies have shown that the combined effect of job stress and an unhealthy lifestyle poses a higher risk for coronary heart disease (CHD) than either factor alone. Among those with job strain, making healthy lifestyle choices can lower the risk of CHD significantly.
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 indicate a heart attack or approaching heart attack. High levels of psychological stress are associated with harmful changes to the blood. Research suggests that stress has the potential to trigger ACS, particularly in patients with heart disease. Studies also suggest that the risk is greatest immediately after the stressful incident, rather than during it.
Researchers are looking at the effectiveness of medications, such as escitalopram, in reducing the risk of mental-stress induced myocardial ischemia (MSIMI). More research is necessary however.
Stress Reduction and Heart Disease. Studies suggest that treatments that reduce psychological distress improve the 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 heart 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 increase in blood pressure, a risk factor for stroke and heart disease.
Effect on the Immune System
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 who are under chronic stress have low white blood cell counts and are more vulnerable to colds. Once a person catches a cold or flu, stress can make symptoms worse. People who carry the herpes virus may be more susceptible to viral activation after they are exposed 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 excess stress and cancer has not been proven. Evidence has shown that job stress is not a significant risk for colorectal, breast, prostate, or lung cancer. However, there may be a connection between stress and cancer survival. One study suggested that cancer patients who were separated from their spouses had lower survival rates than married cancer patients. 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 closely related. They are controlled by many of the same hormones and parts of the nervous system. 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 caused by 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 a person 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.
Eating and Stress
Stress can have varying effects on eating problems and weight. Many Americans report overeating, eating unhealthy foods, or skipping meals due to stress.
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 who are exposed to stress. In addition, the weight gained is often abdominal fat, which increases the risk of diabetes and heart problems.
The release of cortisol, a major stress hormone, appears to boost 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 suggests 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 production of the chemical messenger 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, 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.
Research finds that overeating may be triggered by different stressors in men and women. Women tend to put on extra pounds when dealing with financial and work problems, as well as strained family relationships. Men gain more weight from lack of decision authority at work and difficulty in learning new skills on the job.
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 research is needed to determine whether changes in stress hormones are a cause or a 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 the effects of different personality types, fear of pain, and stress itself. Evidence 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 whether stress is a direct cause of the back pain. Research suggests that the risk of long-term disability from low back pain can be reduced through early treatment for depression and stress.
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 frequently.
Some research suggests that people who experience 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, which prevents stressed people from sleeping or causes them to awaken 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 and Reproductive Dysfunction
Sexual Function. Stress can reduce sexual desire and cause women to be unable to achieve orgasm. The stress response can lead to sexual problems, including 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 affect fertility. Stress hormones have an impact on the hypothalamus, which produces reproductive hormones. This effect may lead to changes in a woman's menstrual cycle, as well as a reduction in a man's sperm count. Stress can also reduce sex drive.
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 weight, and an increased incidence of premature births. Some evidence also suggests that an expectant mother's stress can even influence the way in which her baby's brain and nervous system will react to stressful events. One study found a higher rate of crying and low attention in infants of mothers who had been stressed during pregnancy. These outcomes can have far-reaching effects on a child's life.
Menopause. A drop in estrogen levels during perimenopause and menopause may be responsible for changes in mood precipitated by stress.
Memory, Concentration, and Learning
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 hormones during short-term stress have been associated with enhanced memory storage, improved working memory, 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 lose concentration at work and home, and they may become inefficient and accident-prone. In children, the physiologic responses to chronic stress can interfere with learning. Studies have connected long-term exposure to excess amounts of the stress hormone cortisol to a shrinking of the hippocampus, the brain's memory center. It is not yet known whether this shrinking is reversible.
Skin Disorders. Stress may worsen numerous skin conditions, including hives, psoriasis, acne, and rosacea, and it 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 when people are in mourning.
Teeth and Gums. Stress has now been implicated in increasing the risk for periodontal disease, which can cause tooth loss and has been linked to heart disease.
People who are under chronic stress often turn to alcohol or tobacco for relief. Stress compounds the damage these self-destructive habits cause under ordinary circumstances. Many people also resort to unhealthy eating habits, smoking, or passive activities, such as watching television when they are stressed.
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.