Prolonged fatigue, anxiety and depression: exploring relationships in a primary care sample.

OBJECTIVE: While prolonged fatigue states are frequently comorbid with other forms of distress, they are now the subject of independent aetiological and treatment research. The objective of this study was to use principal component analysis to clarify the relationships between proposed measures of prolonged fatigue and anxiety and depression in data obtained from patients attending primary care.
METHOD: Self-report measures of prolonged fatigue and psychological distress (anxiety and depression) were administered to consecutive ambulatory care patients attending primary care.
RESULTS: Data from 1593 subjects were obtained. A two-factor principal component solution (varimax rotation) demonstrated a clear separation between fatigue-related items (Cronbach's alpha = 0.81) as compared with those items describing anxiety and/or depression (Cronbach's alpha = 0.95). A four-factor solution produced similar results with two factors describing general psychological distress (contrasting anxiety and depression), with two other factors describing the profiles of mental and physical fatigue.
CONCLUSIONS: The results lend weight to the argument that prolonged fatigue states can be measured independently of conventional notions of anxiety and depression in patients attending primary care. Epidemiological, aetiological and treatment research in psychiatry may need to focus greater attention on such prolonged fatigue states.