Michiels, V, de Gucht, V, Cluydts, R et al. · Journal of clinical and experimental neuropsychology · 1999 · DOI
This study tested thinking and memory skills in 29 people with ME/CFS and compared them to 22 healthy people of similar age and education. The results showed that people with ME/CFS had slower thinking speed and difficulty processing information efficiently, but their ability to shift attention or focus on specific visual tasks was not notably impaired. Interestingly, memory problems appeared to stem from difficulty storing new information initially, rather than trouble recalling it later.
This study provides objective neuropsychological evidence that cognitive problems in ME/CFS are real and measurable, specifically highlighting reduced information processing speed as a key feature. Understanding that memory difficulties stem from encoding problems rather than retrieval issues may help inform cognitive rehabilitation strategies and validates the experience of brain fog reported by patients.
This study does not establish the biological cause of processing speed reduction or prove that cognitive symptoms are the primary feature of ME/CFS. The cross-sectional design prevents determination of whether cognitive impairment precedes, follows, or is independent of physical symptom onset. Results cannot be generalized to all ME/CFS patients, particularly those more severely affected.
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
Michiels, V, de Gucht, V, Cluydts, R, & Fischler, B (1999). Attention and information processing efficiency in patients with Chronic Fatigue Syndrome.. Journal of clinical and experimental neuropsychology. https://doi.org/10.1076/jcen.21.5.709.875
BibTeX
@article{mecfsatlas-michiels-1999-attention-information,
author = {Michiels, V and de Gucht, V and Cluydts, R and Fischler, B},
title = {Attention and information processing efficiency in patients with Chronic Fatigue Syndrome.},
journal = {Journal of clinical and experimental neuropsychology},
year = {1999},
doi = {10.1076/jcen.21.5.709.875},
note = {PubMed: 10572289},
url = {https://www.mecfsatlas.com/evidence/michiels-1999-attention-information},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/michiels-1999-attention-information
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