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1994 Definition and Overlap with Psychiatric Conditions

The 1994 U.S. Centers of Disease Control & Prevention (CDC) case definition for the Chronic Fatigue Syndrome (CFS) is flawed because the committee which designed and authored it (under the auspices of the CDC) was constituted by 3 different groups with opposing viewpoints concerning the nature of the illness.

The first group was made up of clinicians who had become experienced with the illness as a result of its recent outbreaks in different parts of the country in both its epidemic and endemic forms. These physicians had seen hundreds of patients with very similar, coherent illnesses of flu-like and neurological symptoms that seemed to follow no usual diagnostic pattern. Initial research had been undertaken that demonstrated immune system abnormalities and the presence of higher than normal levels of antibodies to viruses, as well as the viruses themselves, in the blood and tissues of patients.

The second group on the committee, mainly from the CDC, wished to lump this illness with many other "fatiguing illnesses"—the main symptom for diagnosis would be the extreme fatigue. Such a diagnostic scheme would allow for CFS and primary depression and even cancer to be identified as CFS.

The third group was made up of psychiatrists and others who believed CFS was a psychiatric illness, likely somatoform disorder, neurasthenia, "atypical depression", or somatization disorder.

Hence the 1994 definition was a "compromise by committee". It can diagnose CFS correctly, but could also diagnose a psychiatric disorder as CFS, because of the loose requirement of having only 4 of 7 symptoms to qualify—once the fatigue requirement is met. An individual can be diagnosed as having CFS by having only the following four symptoms:

  1. unrefreshing sleep;
  2. headaches of a new type;
  3. neuropsychological complaints, including problems with short-term memory and concentration;
  4. muscle pain, or multi-joint pain without swelling or redness.

Sleep and memory problems, headaches, and muscle pain, in addition to being a few of the common CFS symptoms, are also symptoms of a variety of other illnesses, including psychiatric illnesses such as depression and anxiety disorder. A strict observance of the Criteria differentiates CFS from Generalized Anxiety Disorder (DSM-IV 300.021); Major Depressive Disorder (DSM IV); and Somatoform Disorders (DSM-IV). (N.B. DSM-IV is the Diagnostic and Statistical Manual of Mental Disorders, 4th edition.)

However, only a physician or psychiatrist thoroughly familiar with the necessary qualifying symptoms of each of the psychiatric disorders and of ME/CFS would be able to make the differential diagnoses. The fact that the four qualifying symptoms, above, for CFS can also represent important qualifying symptoms for psychiatric illness can lead to patients with psychiatric illness being erroneously diagnosed with CFS.

Moreover, the allowance of neurasthenia as a co-morbid illness in CFS diagnosis, as well as the fact that the DSM-IV requirements for neurasthenia provide for an overlap with five of the seven 1994 CFS criteria leads to utter confusion between the two illnesses—depending on whether the conditions' symptoms are interpreted "medically" or "psychiatrically."

Hence a doctor who interprets the patient's symptoms medically arrives at a diagnosis of CFS. But if the doctor interprets the symptoms psychiatrically, the diagnosis is neurasthenia.

It's obvious that many psychiatrists (who are familiar with the neurasthenia diagnosis) might be prone to interpreting CFS symptoms psychiatrically. In fact, the history of CFS has been one of confusion between the actual physical illness and various psychiatric illnesses. Some of this confusion was codified in the 1994 definition.