Epidemiology of unexplained fatigue and major depression in the community: the Baltimore ECA follow-up, 1981-1994.

BACKGROUND: Fatigue is a common, non-specific, subjective symptom associated with several medical and psychiatric illnesses. The purpose of this investigation was to explore further the epidemiology of unexplained fatigue in the general population and the relationship between fatigue and depression.
METHODS: The design was a prospective population-based study. Subjects included community-dwelling adults who were participants of the Baltimore sample of the Epidemiologic Catchment Area Program in 1981 and who were reinterviewed 13 years later. Lay interviewers using the Diagnostic Interview Schedule interviewed subjects.
RESULTS: Number of somatization symptoms and history of a dysphoric episode at baseline were the two strongest predictors of both new onset of fatigue as well as recurrent/chronic fatigue over the 13-year follow-up interval. In addition, individuals who reported a history of unexplained fatigue at baseline as well as during the follow-up, were at markedly increased risk for new onset major depression as compared to those who never reported such fatigue, (RR = 28.4, 95% CI) (11.7, 68.0). Similarly, respondents who developed new fatigue or had remitted fatigue after 1981 were also at increased risk for developing major depression.
CONCLUSIONS: Somatization was the strongest predictor of both new and chronic fatigue with unknown cause. In addition, fatigue was both predictive and a consequence of the depression syndrome.