RELATED STORIES • Fatigue: When to rest, when to worry

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Chronic fatigue syndrome (CFS) is a complicated disorder characterized by extreme fatigue that doesn't improve with bed rest and may worsen with physical or mental activity. Of all chronic illnesses, chronic fatigue syndrome is one of the most mysterious. Unlike infections, it has no clear cause. Unlike conditions such as diabetes or anemia, there's essentially nothing to measure. And unlike conditions such as heart disease, there are relatively few treatment options.

Chronic fatigue syndrome may occur after an infection such as a cold or viral syndrome. It can start during or shortly after a period of high stress or come on gradually without any clear starting point or any obvious cause. Chronic fatigue syndrome is a flu-like condition that can drain your energy and sometimes last for years. People previously healthy and full of energy may experience a variety of symptoms, including extreme fatigue, weakness and headaches as well as difficulty concentrating and painful joints, muscles and lymph nodes.

Women are diagnosed with chronic fatigue syndrome two to four times as often as men are. However, it's unclear whether chronic fatigue syndrome affects women more frequently or if women report it to their doctors more often than men do.

People with chronic fatigue syndrome exhibit signs and symptoms similar to those of most common viral infections. Unlike flu (influenza) symptoms, which usually subside in a few days or weeks, the signs and symptoms of chronic fatigue syndrome can last for months or years. They may come and go frequently with no identifiable pattern.

Primary signs and symptoms
In addition to persistent fatigue, not caused by other known medical conditions, chronic fatigue syndrome has eight possible primary signs and symptoms. These include:

• Loss of memory or concentration
• Sore throat
• Painful and mildly enlarged lymph nodes in your neck or armpits (axillae)
• Unexplained muscle soreness
• Pain that moves from one joint to another without swelling or redness
• Headache of a new type, pattern or severity
• Sleep disturbance
• Extreme exhaustion after normal exercise or exertion

According to the International Chronic Fatigue Syndrome Study Group — a group of scientists, researchers and doctors brought together by the Centers for Disease Control and Prevention (CDC) to determine a standard method for defining and diagnosing chronic fatigue syndrome — a person meets the diagnostic criteria of chronic fatigue syndrome when unexplained persistent fatigue occurs for six months or more with at least four of the eight primary signs and symptoms also present.

Additional signs and symptoms
In addition, people with chronic fatigue syndrome have reported other various signs and symptoms that aren't part of the official definition of chronic fatigue syndrome determined by the International Chronic Fatigue Syndrome Study Group. These include:

• Abdominal pain
• Alcohol intolerance
• Bloating
• Chest pain
• Chronic cough
• Diarrhea
• Dizziness
• Dry eyes and mouth
• Earache
• Irregular heartbeat
• Jaw pain
• Morning stiffness
• Nausea
• Night sweats
• Psychological problems, such as depression, irritability, anxiety disorders and panic attacks
• Shortness of breath
• Tingling sensations
• Weight loss

If you have chronic fatigue syndrome, your symptoms may peak and become stable early on, and then come and go over time. Some people go on to recover completely, while others grow progressively worse.

Doctors don't know the cause of chronic fatigue syndrome. Several possible causes have been proposed, including:

• Iron deficiency anemia
• Low blood sugar (hypoglycemia)
• History of allergies
• Virus infection, such as Epstein-Barr virus or human herpesvirus 6
• Dysfunction in the immune system
• Changes in the levels of hormones produced in the hypothalamus, pituitary glands or adrenal glands
• Mild, chronic low blood pressure (hypotension)

The cause of chronic fatigue syndrome may be an inflammation of the pathways of the nervous system as a response to an autoimmune process, but with nothing measurable in the blood like in other autoimmune diseases, such as rheumatoid arthritis or lupus. Chronic fatigue syndrome may also occur when a viral illness is complicated by a dysfunctional immune system. Some people with chronic fatigue syndrome may have a low blood pressure disorder that triggers the fainting reflex.

In many cases, however, no serious underlying infection or disease is proved to specifically cause chronic fatigue syndrome. Lack of medical knowledge and understanding of chronic fatigue syndrome has made determining and describing the characteristics of the condition difficult.

Women are diagnosed with chronic fatigue syndrome two to four times as often as men are, but sex isn't a proven risk factor for the condition. Because the cause of the condition is unknown, doctors have yet to determine and confirm definite risk factors for the disease.

Fatigue can be a symptom of many illnesses, such as infections or psychological disorders. In general, see your doctor if you have persistent or excessive fatigue. Severe fatigue that prevents you from fully participating in activities at home, work or school may be a sign of an underlying medical condition.

A diagnosis of chronic fatigue syndrome is based on exclusion. This means that before arriving at a diagnosis, a doctor has ruled out any other disease or condition that may be causing your fatigue and related symptoms.

In general, doctors find it difficult to diagnose chronic fatigue syndrome because it has some of the same signs and symptoms as many other diseases. There's no diagnostic or laboratory procedure to confirm the presence of chronic fatigue syndrome.

Doctors exclude certain conditions before considering a diagnosis of chronic fatigue syndrome. These include:

• Having an active medical condition that often results in fatigue, such as low levels of thyroid hormones (hypothyroidism) or sleep apnea
• Using medicines that may cause fatigue
• Having a relapse of a previously treated illness that can result in fatigue, such as cancer
• Having had a past or current diagnosis of a major depressive disorder or other psychiatric illness such as schizophrenia or an eating disorder
• Abusing alcohol or another substance
• Being severely obese, as defined by a body mass index (BMI) of 45 or greater

Over time, be alert to any new cues that might indicate that the problem is caused by something other than chronic fatigue syndrome. When other diseases or conditions are excluded, your doctor may then determine if your illness meets the CFS-specific criteria.

Possible complications of chronic fatigue syndrome include:

• Depression, related both to symptoms and lack of diagnosis
• Side effects and adverse reactions related to medication treatments
• Side effects and adverse reactions associated with lack of activity (deconditioning)
• Social isolation caused by fatigue
• Lifestyle restrictions
• Missing work

The long-term outlook for people with chronic fatigue syndrome varies and is unpredictable. Some people recover completely after six months to a year. For others, total recovery takes longer.

There's no specific treatment for chronic fatigue syndrome. In general, doctors aim to relieve symptoms by using a combination of treatments, which may include:

• Lifestyle changes. Your doctor may encourage you to slow down and to avoid excessive physical and psychological stress. This may save your energy for essential activities at home or work and help you cut back on less important activities.
• Gradual but steady exercise. Often with the help of a physical therapist, you may be advised to begin a graduated exercise program in which physical activity gradually increases. This can help prevent or decrease the muscle weakness caused by prolonged inactivity. In addition, your energy level can often improve significantly.
• Treatment of psychiatric problems. Doctors can treat problems often related to chronic fatigue syndrome, such as depression, with medication or behavior therapy — learning to change your behavior to reduce the symptoms of a certain disease or condition — or a combination of the two. If you're depressed, medications such as tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs) may help. Antidepressants may also help improve sleep and relieve pain. Tricyclic antidepressants include amitriptyline (Limbitrol, Triavil — both of which are multi-ingredient drugs that contain amitriptyline), desipramine (Norpramin) and nortriptyline (Aventyl, Pamelor). SSRIs include fluoxetine (Prozac, Sarafem), paroxetine (Paxil), sertraline (Zoloft) and bupropion (Wellbutrin).
• Treatment of existing pain. Acetaminophen (Tylenol, others) or nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen (Advil, Motrin, others) may be helpful to reduce pain and fever.
• Treatment of allergy-like symptoms. Antihistamines such as fexofenadine (Allegra) and cetirizine (Zyrtec) and decongestants that contain pseudoephedrine (Sudafed, Dimetapp) may relieve allergy-like symptoms such as runny nose.
• Treatment of low blood pressure (hypotension). The drugs fludrocortisone (Florinef), atenolol (Tenormin), and midodrine (ProAmatine) may be useful for certain people with chronic fatigue syndrome.
• Treatment for problems of the nervous system. Symptoms such as dizziness and extreme skin tenderness can sometimes be relieved by clonazepam (Klonopin). Your doctor may prescribe medications such as lorazepam (Ativan) and alprazolam (Xanax) to relieve symptoms of anxiety.

Some medications can cause side effects or adverse reactions that may be worse than the symptoms of chronic fatigue syndrome. Talk to your doctor before starting any treatment for chronic fatigue syndrome.

Because the cause of chronic fatigue syndrome remains unknown, there's no known way to prevent the illness from occurring. Be aware of the symptoms and signs of chronic fatigue syndrome and seek the help of your doctor to manage them if they occur.

Learning how to manage fatigue can help you improve your level of functioning and your quality of life despite your symptoms. You may work with a rehabilitation medicine specialist who can teach you how to plan activities to take advantage of times when you usually feel better.

These important self-care steps can help you to maintain good general health:

• Reduce stress. Develop a plan to avoid or limit overexertion and emotional stress. Allow yourself time each day to relax. That may mean learning how to say no without guilt. If possible, don't change your routine totally. People who quit work or drop all activity tend to do worse than those who remain active.
• Get enough sleep. Getting sufficient sleep is essential. In addition to allotting enough time for sleep, practice good sleep habits such as going to bed and getting up at the same time each day and limiting daytime napping.
• Exercise regularly. You may need to start slow and build up gradually. But exercising regularly often improves symptoms. Many people find exercises such as walking, swimming, biking and water aerobics to be helpful. A physical therapist may help you develop a home exercise program. Stretching, good posture and relaxation exercises also can be helpful.
• Pace yourself. Keep your activity on an even level. If you do too much on your good days, you may have more bad days.
• Maintain a healthy lifestyle. Try to eat a balanced diet, drink plenty of fluids, limit your caffeine intake, stop smoking, get adequate rest and exercise regularly. Find a hobby or career that is enjoyable and fulfilling for you.

The experience of chronic fatigue syndrome varies from person to person. For many people, however, the symptoms are more bothersome early in the course of the illness and then gradually decrease. Some people recover completely with time. Emotional support and counseling may help you and your loved ones deal with the uncertainties and restrictions of chronic fatigue syndrome.

You may find it therapeutic to join a support group and meet other people with chronic fatigue syndrome. Support groups aren't for everyone, and you may find that a support group adds to your stress rather than relieves it. Experiment and use your own judgment to determine what's best for you.

Some makers of various dietary supplements and herbal remedies claim these substances have potential benefits for people with chronic fatigue syndrome, but the effectiveness of these substances for treating the condition hasn't been proved in controlled studies. Though a product may be of "natural" origin, that doesn't ensure its safety. Dietary supplements and herbal preparations can have potentially harmful side effects and may dangerously interfere or interact with prescription medications. Talk to your doctor before using any unprescribed remedy.