Jason, Leonard A, Kot, Bobby, Sunnquist, Madison et al. · Health psychology and behavioral medicine · 2015 · DOI
Researchers studied which symptoms are most important for diagnosing ME/CFS by comparing patients with the condition to people without it. They found that four main symptoms stood out: extreme fatigue, symptom worsening after activity (called post-exertional malaise), thinking or memory problems, and sleep that doesn't feel refreshing. Using these core symptoms could help doctors diagnose ME/CFS more reliably.
Improving diagnostic criteria is crucial for ME/CFS patients because inconsistent definitions have historically led to underdiagnosis, delayed treatment, and research heterogeneity. Empirically-derived core symptoms could standardize diagnosis across healthcare settings, reducing patient suffering and enabling more rigorous research. This work supports the shift toward objective, measurable criteria that better reflect the biological reality of the condition.
This study does not prove that these four symptoms are the only diagnostic features of ME/CFS or that they are sufficient for diagnosis without clinical evaluation. It cannot establish whether these symptoms are causes or consequences of ME/CFS, nor does it validate whether this symptom set generalizes to all ME/CFS populations (particularly different ages, ethnicities, or disease stages). The cross-sectional design cannot determine whether symptom combinations remain reliable over time or predict disease progression.
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
Jason, Leonard A, Kot, Bobby, Sunnquist, Madison, Brown, Abigail, Evans, Meredyth, Jantke, Rachel, et al. (2015). Chronic Fatigue Syndrome and Myalgic Encephalomyelitis: Toward An Empirical Case Definition.. Health psychology and behavioral medicine. https://doi.org/10.1080/21642850.2015.1014489
BibTeX
@article{mecfsatlas-jason-2015-chronic-fatigue-3,
author = {Jason, Leonard A and Kot, Bobby and Sunnquist, Madison and Brown, Abigail and Evans, Meredyth and Jantke, Rachel and Williams, Yolonda and Furst, Jacob and Vernon, Suzanne D},
title = {Chronic Fatigue Syndrome and Myalgic Encephalomyelitis: Toward An Empirical Case Definition.},
journal = {Health psychology and behavioral medicine},
year = {2015},
doi = {10.1080/21642850.2015.1014489},
note = {PubMed: 26029488},
url = {https://www.mecfsatlas.com/evidence/jason-2015-chronic-fatigue-3},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/jason-2015-chronic-fatigue-3
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