Unexplained fatigue syndromes in a multinational primary care sample: Specificity of definition and prevalence and distinctiveness from depression and generalized anxiety

Objective: The authors investigated whether narrow definitions of unexplained fatigue syndromes that require additional minor somatic symptoms are more strongly associated with psychiatric morbidity than wider ones. Method: This was a secondary analysis of the World Health Organization Collaborative Project on Psychological Problems in General Health Care. A total of 5,438 primary care patients from 14 countries were assessed with the Composite International Diagnostic Interview. Results: The prevalence of fatigue syndromes fell from 7.99 to 1.69 as somatic criteria were added. Patients with depression or anxiety were more likely to report unexplained fatigue, but this association was stronger for definitions of unexplained fatigue with more somatic criteria. Conclusions: Definitions of unexplained fatigue syndromes that require more somatic criteria selected more patients with psychiatric disorders in this culturally diverse sample. These findings might have implications for the revision of existing international diagnostic criteria for neurasthenia or chronic fatigue syndrome.