Specific to CFS patients

It is not the case that patients with CFS become less intelligent. Many patients are concerned that they are "dementing." Dr. Lange stated that she has not seen a CFS patient with dementia. CFS is not a degenerative neurological disorder. I.Q. tests are divided between steady state functions, well-entrenched information firmly planted in the brain, and more transient functions. The steady state information does generally not decay in patients with CFS.

In Dr. Lange's experience, the major problem with CFS patients is the slowing down of information processing. It affects working memory, the ability to keep pieces of information in mind for immediate use. For instance, hearing a phone number and then being able to recall it five minutes later to make the call. For most CFS patients, that is impossible. The resulting frustration then makes the cognitive problem worse.

Dr. Denise Park has called this the "premature aging of the brain," meaning that the brain in a thirty-five-year-old fibromyalgia patient in Park's study (Park Dl et al, "Cognitive Function in Fibromyalgia Patients," Arthritis & Rheumatism 44, No. 9 (2001): 2125-2133) reflected the neuropsychological testing performance of a person 20 years older.