Diagnosis

Post-Lyme Syndrome. A delayed response or recurrence of previously treated Lyme disease (called post-Lyme syndrome) may be mistaken for chronic fatigue syndrome in people who live in areas where there are outbreaks. Although the two disorders are similar, one study found that CFS patients reported more flu-like syndromes and those with post-Lyme disease performed significantly worse on tests of mental functioning and motor control. If CFS patients are mistakenly diagnosed and treated for Lyme disease, they may take prolonged courses of antibiotics that can have serious side effects, ultimately doing more harm than good.

Psychosis and Severe Mental Disorders. The Centers for Disease Control (CDC), which set up the definitions in the US for research in chronic fatigue syndrome, recognize depression as one of the symptoms of CFS. However, the CDC rules out chronic fatigue syndrome as a diagnosis for anyone with a history of major depression or other severe psychiatric disorders, including bipolar disorder and schizophrenia. Depression or anxiety not associated with a psychosis or severe mental illness does not rule out CFS.

Symptoms of major depression include the following:

• A depressed mood every day
• Significant weight gain or loss (10% or more of an individual's typical body weight)
• Insomnia or excessive sleeping
• Restlessness or a sense of being slowed down
• Low energy every day
• Worthless or inappropriately guilty feelings
• An inability to concentrate or to make decisions
• Suicidal thoughts

Major depression is likely to be the responsible condition in the presence of several of these symptoms and if there are no physical symptoms (such as sore throat, aches and pains, or fever). And the longer fatigue has continued without such physical symptoms, the more likely that the diagnosis is depression.

Of note, a persistent form of minor depression called dysthymia may be more difficult to differentiate from CFS and may actually account for a subset of CFS cases. Dysthymia is characterized by many of the same symptoms that occur in major depression but they are less intense and last much longer, at least two years. The symptoms of dysthymia have been described as a "veil of sadness" that covers most activities.