Complications:

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, vessels, and muscles) become chronically over- 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.

Psychological Effects of Stress

Studies suggest that the inability to adapt to stress is associated with the onset of depression or anxiety. In one study, two-thirds of subjects who experienced a stressful situation had nearly 6 times the risk of developing depression within that month.

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 nerve 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.

Heart Disease

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:

• Sudden stress increases the pumping action and rate of the heart, while at the same time causing the arteries to constrict (narrow). This restricts blood flow to the heart. A 2002 study suggested that such actions may be responsible for some cases of acute stress that have been associated with a higher risk for serious heart problems. These problems include heart rhythm abnormalities and heart attacks, and even death in people with heart disease.
• 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 blood to become stickier (possibly in preparation of potential injury), increasing the likelihood of an artery-clogging blood clot.
• Stress appears to impair the clearance of fat molecules in the body, raising blood-cholesterol levels, at least temporarily.
• 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.
• Chronic stress may lead to the production of immune factors called cytokines, although study results vary widely. Cytokines produce an inflammatory response that is now believed to be responsible for damaging the arteries. Such damage contributes to heart disease. New studies indicate that some people under stress may have increased levels of C-reactive protein (CRP), a risk marker for heart attack. Each 1 mg/L increase in CRP has been linked to a 20% increased risk of myocaridal ischemia, a condition that signals poor blood flow to the heart muscle.
• Stress causes the body to release inflammatory markers into the bloodstream. These markers may worsen heart disease or increase the risk of 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 in the inner lining of their blood vessels. In one 20-year study, for example, men who periodically measured highest on the stress scale were twice as likely to have high blood pressure as those with normal stress.

Evidence is still needed to confirm any clear-cut relationship between stress and heart disease. For example, a 2002 study in Scotland found no greater risk for actual heart disease or heart events even in men who reported higher mental stress. In fact, higher stress was associated with fewer heart events. Men with high stress levels did tend to complain of chest pain and to go to the hospital for it more often than those with lower stress. They also went to the hospital more often.

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. In one study, men were more apt than women to use alcohol or eat less healthily in response to stress, which might account for their higher heart risks from stress. Different stressors may affect genders differently. In one study, work stress was associated with a higher risk for heart disease in men, but marital stress -- not work stress -- was associated with more severe heart disease in women with existing heart problems.

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.

Acute emotional stress can create abnormal heartbeats. MRI studies show that asymmetric brain activity may play a role in making a stressed heart susceptible to ventricular arrhythmias by creating electrical instability. In some patients, this can cause sudden cardiac death.

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 2007 review of studies on blood qualities, coagulation, fibrinolysis, and platelet reactivity 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 reduce the risk of heart attacks by up to 75% 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.

Stroke

One survey revealed that men who had a more intense response to stressful situations, such as waiting in line or problems at work, were more likely to have strokes than those who did not report such distress. In some people, prolonged or frequent mental stress causes an exaggerated increase in blood pressure.

Effect on the Immune System

Chronic stress affects the immune system in complicated ways, and may have various results.

Susceptibility to Infections. Chronic stress appears to blunt the immune system's response to infections, and may even impair a person's response to immunizations. Several studies have shown 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 or HIV may be more susceptible to viral activation following exposure to stress. Even more serious, some research has found that HIV-infected men with high stress levels progress more rapidly to AIDS when compared to those with lower stress levels.

Inflammatory Response. Some evidence suggests that chronic stress triggers an over-production of certain immune factors called cytokines. In excess levels, these chemicals can have very damaging effects. A recent study found that students unable to cope with stress had high levels of TNF-alpha, an inflammatory cytokine. Such findings may partly explain the association between chronic stress and numerous diseases, including heart disease and asthma.

Cancer

Whether or not stress causes or aggravates cancer is not entirely clear. One study reported no association between stressful life events and recurrence in women who had been treated for breast cancer. Nevertheless, some animal studies suggest that lack of control over stress (not simply stress itself) had negative effects on immune function and contributed to tumor growth.

That being said, a 2007 study found that stress activates a gene that may cause metastatic cancer, as measured by increasing levels of the marker AGR2.

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. Stress is also known to be one cause of hyponatremia (low plasma sodium levels) in cancer patients. Fortunately, this imbalance can be corrected with drugs called AVP-receptor agonists, developed for use in heart failure.

Gastrointestinal Problems

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 to ulcers, or sustain existing ulcers. Some experts estimate that social and psychological factors play some contributing role in 30 - 60% of peptic ulcer cases, whether they are caused by H. pylori or NSAIDs. In any case, some experts believe that the anecdotal relationship between stress and ulcers is so strong that attention to psychological factors is still warranted.

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. One study, for example, found that while short-term (over the previous month) stress did not significantly exacerbate ulcerative colitis symptoms, long-term perceived stress tripled the rate of flare-ups compared to patients who did not report feelings of stress.

Eating and Stress

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. A 2005 study showed 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 have been found to significantly increase levels of tryptophan and large neutral amino acids. This produces serotonin, which improves mood and performance under stress.

A 2007 study proposes 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.

Weight Loss. Some people suffer a loss of appetite and lose weight during periods of stress. In rare cases, stress may trigger hyperactivity of the thyroid gland, stimulating appetite but causing the body to burn up calories at a faster than normal rate.

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.

Diabetes

Chronic stress has been associated with the development of insulin resistance, a condition in which the body is unable to use insulin effectively to regulate glucose (blood sugar). Insulin resistance is a primary factor in diabetes. In the Healthy Women Study, a large population of healthy women was studied for 15 years. Very stressful life events and severe depression greatly increased the risk of developing insulin resistance.

In another study of more than 33,000 Swedish workers, the development of type 2 diabetes was strongly correlated with work stress and low emotional support. However, the effect was seen in women, but not in men.

Stress can also exacerbate existing diabetes by impairing the patient's ability to manage the disease effectively.

Pain

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. According to a study on patients with rheumatoid arthritis, however, stress management techniques do not appear to have much effect on arthritic pain. 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). One study suggested that women with migraines tend to have personalities that over-respond to stressful situations.

Sleep Disturbances

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 (NREM) sleep.

Sexual and Reproductive Dysfunction

Sexual Function. Stress can lead to diminished sexual desire and an inability to achieve orgasm in women. Stress response can cause androgen levels to drop, causing temporary impotence in men. Part of the stress response involves the release of brain chemicals that constrict the smooth muscles of the penis and its arteries. This constriction reduces the blood flow into and increases the blood flow out of the penis, which can prevent erection.

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. Stress may even affect fertility. Stress hormones have an impact on the hypothalamus gland, which produces reproductive hormones. Severely elevated cortisol levels can even shut down menstruation. One small study reported a significantly higher incidence of pregnancy loss in women who had both high stress and prolonged menstrual cycles. Another reported that women with stressful jobs had shorter periods than women with low-stress jobs.

Effects on Pregnancy. Old wives' tales about a pregnant woman's emotions affecting her baby may have some credence. Stress may cause physiologic 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. Estrogen replacement therapy can soften this response to stressful events.

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 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. In a study of 20 men and 20 women, those whose cortisol levels increased in response to unpleasant, emotionally arousing photos had less memory recall later than those whose cortisol levels did not rise.

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. Chronic stress in older people may play an even more important role in memory loss than the aging process. In one study, for example, older adults with low stress hormone levels tested as well as younger adults in cognitive tests; those with higher stress levels tested 20 - 50% lower.

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.

Other Disorders

Allergies. Stress has been related to skin allergies. Some research suggests that stress, not indoor pollutants, may actually be a cause of the so-called sick-building syndrome. Sick-building syndrome produces allergy-like symptoms, such as eczema, headaches, asthma, and sinus problems, in office workers.

Compulsive Hoarding. People with obsessive-compulsive disorder (OCD) and compulsive hoarding are far more likely to have experienced a traumatically stressful event than people with OCD who are not hoarders. Hoarders who have experienced traumatic events have significantly more severe hoarding than those who have not been traumatized. The strongest association with traumatic stress is found in the clutter factor of compulsive hoarding, rather than in difficulty discarding objects.

Chronic Fatigue. Stress increases the risk of developing chronic fatigue syndrome, although studies suggest that high levels of emotional instability may genetically predispose someone to the syndrome.

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, which is disease in the gums that can cause tooth loss.

Substance Abuse

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 a national survey, released in February 2006, 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. One study indicated that nicotine has calming effects in women but not in men. In fact, in the study, smoking increased aggression in men.

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.