Smith, A P, Borysiewicz, L, Pollock, J et al. · Psychological medicine · 1999 · DOI
This study tested whether people with ME/CFS get tired more quickly during mental tasks than healthy people. Researchers compared 67 ME/CFS patients with 126 healthy controls while they performed attention tests over a long session. ME/CFS patients performed worse than healthy people, and the gap widened as fatigue set in, suggesting they struggle more with mental tiredness.
This study provides objective evidence that ME/CFS patients experience real, measurable cognitive fatigue beyond subjective complaints, validating patient experiences of worsening performance with activity. Understanding whether fatigue in ME/CFS reflects a continuum or distinct pathology helps guide research into underlying biological mechanisms and informs rehabilitation approaches.
This study does not establish the biological cause of acute fatigue susceptibility in ME/CFS (e.g., mitochondrial dysfunction, immune dysregulation) nor does it prove whether the fatigue is primarily central (brain-based) or peripheral (muscular). The cross-sectional design cannot determine causality or whether fatigue susceptibility precedes or results from CFS development.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Smith, A P, Borysiewicz, L, Pollock, J, Thomas, M, Perry, K, & Llewelyn, M (1999). Acute fatigue in chronic fatigue syndrome patients.. Psychological medicine. https://doi.org/10.1017/s003329179800748x
BibTeX
@article{mecfsatlas-smith-1999-acute-fatigue,
author = {Smith, A P and Borysiewicz, L and Pollock, J and Thomas, M and Perry, K and Llewelyn, M},
title = {Acute fatigue in chronic fatigue syndrome patients.},
journal = {Psychological medicine},
year = {1999},
doi = {10.1017/s003329179800748x},
note = {PubMed: 10218920},
url = {https://www.mecfsatlas.com/evidence/smith-1999-acute-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/smith-1999-acute-fatigue
Contribute
Private, reviewed by a human. Not a public comment thread.