Existing case definitions for CFS appear to characterize a group of people with prolonged fatigue and impaired ability to function. The validity and superiority of any particular case definition are not well established. Surveys suggest that the prevalence of CFS in community populations is less than 1%. Precise estimates of rates of recovery, improvement and/or relapse from CFS are not available. Although several therapies have been studied, potential benefits as well as harms of most therapies are not well established. Behavioral interventions that emphasize increasing activity levels may improve quality of life and function in some people with CFS.
