Cognitive Disturbances in Chronic Fatigue Syndrome and Fibromyalgia


Please comment on cognitive disturbances associated with chronic fatigue syndrome (myalgic encephalomyelitis) and fibromyalgia syndrome.


(from Neil M. Busis, MD, 04/27/2000)
There are 2 commonly accepted diagnostic criteria for chronic fatigue syndrome. The first set,[1] from the Centers for Disease Control, do not include cognitive dysfunction. These are:

Clinically evaluated, medically unexplained fatigue of at least 6 months' duration that is of new onset, is not a result of ongoing exertion, is not substantially alleviated by rest, and constitutes a substantial reduction in previous levels of activity. In addition, these criteria demand that the patient have at least 4 of the following symptoms:

  • subjective memory impairment
  • tender lymph nodes
  • muscle pain
  • joint pain
  • headache
  • unrefreshing sleep
  • postexertional malaise lasting more than 24 hours.

However, the Oxford diagnostic criteria[2] include cognitive dysfunction as a core feature of this syndrome. This scheme defines the syndrome as one of severe, disabling fatigue of at least 6 months' duration that:

affects both physical and mental functioning, and is present for more than 50% of the time. Other symptoms, particularly myalgia and sleep and mood disturbance, may also be present.

Neuropsychological tests of patients with chronic fatigue syndrome support the presence of reduced information processing speed and efficiency and suggest a global non-modality-specific attentional dysfunction in these patients.[3]

The duration of symptoms relates to the degree of cognitive difficulties.[4] Participants with long-duration chronic fatigue syndrome (median, 18 years; n = 258) reported a large number of specific cognitive difficulties that were greater in severity than those reported by participants with short-duration chronic fatigue syndrome (median, 3 years; n = 28).

Cognitive disturbances can also be seen in patients with fibromyalgia. For example, Grace and colleagues[5] found that fibromyalgia patients performed more poorly on tests of immediate and delayed recall and sustained auditory concentration, and their ratings of both their memory abilities and sleep quality were lower than those of controls. Perceived memory deficits of these patients were disproportionately greater than their objective deficits. There were significant correlations between performance on memory and concentration measures and scores on questionnaires of pain severity and trait anxiety.


1.Fukuda K, Straus S, Hickie I, Sharpe M, Dobbins J, Komaroff A. The chronic fatigue syndrome: a comprehensive approach to its definition and study. Ann Intern Med. 1994;121:953-959 
2.Sharpe M, Archard LC, Banatvala JE. A report - chronic fatigue syndrome: guidelines for research. J R Soc Med. 1991;84:118-121. 
3.Michiels V, de Gucht V, Cluydts R, Fischler B. Attention and information processing efficiency in patients with Chronic Fatigue Syndrome. J Clin Exp Neuropsychol. 1999;21:709-729 
4.Friedberg F, Dechene L, McKenzie MJ II, Fontanetta R. Symptom patterns in long-duration chronic fatigue syndrome. J Psychosom Res. 2000;48:59-68. 
5.Grace GM, Nielson WR, Hopkins M, Berg MA. Concentration and memory deficits in patients with fibromyalgia syndrome. J Clin Exp Neuropsychol. 1999;21:477-487.