In this prospective study, 137 patients with chronic fatigue syndrome were followed-up at a 1-year interval to determine factors relating to outcomes. Nearly two thirds reported an improvement on direct ratings of change. In analyses with fatigue and functional impairment at follow-up as the criteria, and controlling for earlier status, poorer outcomes were predicted by illness duration, subjective cognitive difficulty, and somatic symptoms; there was no influence of anxiety, depression, or general emotional distress. Fatigue was also predicted by information-seeking, and impairment by behavioral disengagement and a low internal locus of control. The belief that one's actions can influence outcomes modified the relationship between illness accommodation and both fatigue and impairment; adverse outcomes were associated with accommodating to illness only in the context of lower levels of perceived control. Thus, it is suggested that interventions that either discourage avoidance of activity or enhance perceived control could benefit the course of the illness.
