Diagnosis

A 2001 study suggested that patients with depression and those with CFS differ in how they perceive their illnesses:

• Patients with depression had significantly lower self-esteem, more thought distortions (for instance, focusing on the negative or personalizing their situations), and believed their conditions stemmed from psychological factors.
• CFS patients, even those with concurrent depression or dysthymia, tended to identify medical causes as the source of their problems and to focus on physical symptoms.

A number of patients who are diagnosed with CFS report having felt depressed before the onset of chronic fatigue. Many other CFS patients, however, felt alert and mentally sound before the onset of CFS symptoms. Many of these previously healthy patients become depressed and anxious because they feel so exhausted all the time. CFS may also lead to highly stressful socioeconomic situations, such as social isolation and poverty, that can contribute to and even cause emotional disorders in susceptible individuals, which in turn can worsen CFS.

Sleep Disturbances. Certain sleep disorders may cause persistent fatigue and be confused with CFS:

• Sleep apnea is a common disorder that can cause daytime fatigue without the patient being aware of the problem. This is actually a breathing disorder often marked by loud snoring and thrashing in bed. A person may not realize the problem exists unless it is brought to his or her attention by a sleeping partner or observer.
• Narcolepsy is a peculiar and rare disorder in which a person suddenly falls asleep without any previous signs of fatigue.
• Other sleep disorders that cause daytime fatigue include insomnia and restless legs syndrome.

In addition, many patients with CFS suffer from sleep problems. A 2004 study found that over 80 percent of CFS patients experienced at least one type of sleep disorder. Non-restorative sleep and nighttime restlessness were the most common complaints.

Conditions that Cause Joint Pain, Muscle Aches, or Both. A number of illnesses cause one or more of CFS symptoms including arthritic symptoms, fever, and fatigue.

Severe Obesity. People who are severely obese often have symptoms of chronic fatigue because of the stress imposed by the weight. People who are obese are also at particular risk for sleep apnea, which can confuse the diagnosis.

Other Medical Conditions that Usually Rule Out CFS. Many diseases, both benign and serious, can fully explain prolonged or chronic fatigue, including hepatitis, anemia, hemochromatosis (a hereditary disease caused by iron overload) infections, various forms of cancer, neuromuscular diseases (such as myasthenia gravis), hypothyroidism, and diabetes.

Drugs and Alcohol. Fatigue is a side effect of many prescription and over-the-counter medications, such as antihistamines. In addition, dependency on or abuse of alcohol or illicit drugs may manifest as chronic fatigue. Medications should be considered as a possible cause of fatigue if an individual has recently started, stopped, or changed medicines. Withdrawal from caffeine can produce depression, fatigue, and headache.

Conditions That Do Not Rule Out Chronic Fatigue Syndrome

Many diagnosable conditions cause symptoms similar to CFS, but they can overlap. As such, their presence does not necessarily rule CFS out as a co-disorder. In fact, CFS patients appear to be at high risk for developing depression and additional health problems, particularly those with similar symptoms (for example, fibromyalgia, irritable bowel syndrome, chronic pelvic pain, chemical sensitivities, and temporomandibular disorder).

Some tests may be positive for one or more of these diseases. However, if the results are ambiguous or weak or if they have been treated successfully, CFS should not be ruled out if the patient still also meets the criteria for it.