Santamarina-Pérez, Pilar, Freniche, Verónica, Eiroa-Orosa, Francisco Jose et al. · Medicina clinica · 2011 · DOI
This study tested whether depression explains the thinking and memory problems that people with ME/CFS experience. Researchers gave 57 women with ME/CFS a variety of cognitive tests measuring attention, memory, and processing speed, then compared results between those with and without depression. The findings showed that cognitive problems were present in ME/CFS patients regardless of whether they had depression, suggesting that the brain fog and thinking difficulties are part of ME/CFS itself, not caused by depression.
This finding is important because it validates that cognitive impairment in ME/CFS is a core disease feature rather than a secondary effect of depression—a distinction that affects how patients are understood and treated. It supports the biological basis of 'brain fog' and encourages clinicians to recognize cognitive dysfunction as a hallmark symptom requiring specific clinical attention.
This study does not establish causality or determine the underlying biological mechanisms of cognitive impairment in ME/CFS. It does not prove that depression and cognitive impairment are completely independent; it only shows they are not statistically correlated in this sample. The findings also cannot be generalized to men or to ME/CFS patients without depression, as the study included only women and used a clinical sample.
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
Santamarina-Pérez, Pilar, Freniche, Verónica, Eiroa-Orosa, Francisco Jose, Llobet, Guillem, Sáez, Naia, Alegre, José, et al. (2011). [The role of depression in cognitive impairment in patients with chronic fatigue syndrome].. Medicina clinica. https://doi.org/10.1016/j.medcli.2010.07.022
BibTeX
@article{mecfsatlas-santamarina-prez-2011-role-depression,
author = {Santamarina-Pérez, Pilar and Freniche, Verónica and Eiroa-Orosa, Francisco Jose and Llobet, Guillem and Sáez, Naia and Alegre, José and Jacas, Carlos},
title = {[The role of depression in cognitive impairment in patients with chronic fatigue syndrome].},
journal = {Medicina clinica},
year = {2011},
doi = {10.1016/j.medcli.2010.07.022},
note = {PubMed: 21145567},
url = {https://www.mecfsatlas.com/evidence/santamarina-prez-2011-role-depression},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/santamarina-prez-2011-role-depression
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