title: The chronic fatigue syndrome--an update.
abstract: BACKGROUND
  In this article, current scientific knowledge on the chronic fatigue syndrome (CFS) is reviewed. The US case definition of CFS (the CDC-definition) is most widespread in research and clinical practice. Estimates of prevalence vary from 0.2% to above 2%. The female-male ratio is approximately 3:1.
  
  
  METHODS
  Severe fatigue is the dominating complaint; it is worsened from exertions and not substantially relieved by rest. In addition, the patients might have a varying combination of accompanying symptoms. Clinical evaluation should be based upon standardized guidelines, including an assessment of functional impairments.
  
  
  METHODS
  The pathophysiology should be interpreted within a biopsychosocial framework. Present knowledge suggests that certain genetic polymorphisms and personality traits might be regarded as predisposing factors, some infections and severe psychosocial stress constitute precipitating factors, whereas disturbances of immunity, skeletal muscle, cognitive abilities, endocrine control and cardiovascular homeostasis are possible perpetuating factors.
  
  
  METHODS
  Cognitive behavioural therapy and graded exercise therapy are of proven value in randomized controlled trials. Several pharmaceutical measures have been explored and found to have no beneficial effect. Most patients might expect long-term improvement, but full recovery is rare; however, the prognosis is better among adolescents.
authors.affiliation: Department of Pediatrics, Rikshospitalet-Radiumhospitalet Medical Centre, Oslo, Norway. brwylle@online.no
authors.forename: Vegard Bruun
authors.initials: VB
authors.lastname: Wyller
mesh_terms: D015984:Causality; D002490:Central Nervous System / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology*; D015928:Cognitive Behavioral Therapy / Q000592:standards; D005081:Exercise Therapy / Q000592:standards; D015673:Fatigue Syndrome, Chronic / Q000503:physiopathology* / Q000523:psychology* / Q000628:therapy; D006801:Humans; D018482:Muscle, Skeletal / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology*; D013315:Stress, Psychological / Q000150:complications / Q000276:immunology; D014777:Virus Diseases / Q000150:complications / Q000276:immunology