Manu, P, Lane, T J, Matthews, D A · Annals of internal medicine · 1988 · DOI
This study looked at 135 people with severe fatigue lasting at least 6 months to see how many actually had ME/CFS. The researchers found that only 6 patients (about 4%) met the criteria for ME/CFS, while most of the others had psychiatric conditions like depression or anxiety that were causing their fatigue. This suggests that ME/CFS is quite rare among people presenting with fatigue symptoms.
This early study challenges assumptions about the prevalence of ME/CFS among fatigued patients and highlights the importance of thorough differential diagnosis. Understanding that most persistent fatigue has psychiatric or medical causes rather than ME/CFS helps guide appropriate clinical evaluation and treatment pathways for patients seeking answers.
This study does not prove that ME/CFS patients have psychiatric disorders as a cause of their condition—the psychiatric diagnoses were found in patients who did not meet ME/CFS criteria. The study also cannot establish whether psychiatric comorbidity exists in those with confirmed ME/CFS, and the 1988 case definition used may not align with modern diagnostic criteria. Cross-sectional design prevents determination of causality or temporal relationships.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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