Jason, Leonard A, Sunnquist, Madison, Brown, Abigail et al. · Journal of health psychology · 2016 · DOI
This study looked at whether ME/CFS might actually be two different illnesses depending on which diagnostic criteria doctors use. Researchers compared two sets of diagnostic guidelines and found that the stricter ME criteria (International Consensus Criteria) identified patients who were more severely ill and had greater functional problems than the broader chronic fatigue syndrome criteria. This suggests that the criteria doctors use to diagnose the condition can significantly affect who gets identified as having the illness.
Understanding whether different diagnostic criteria identify distinct patient populations is crucial for ME/CFS research and clinical practice. This finding suggests that patients meeting the stricter ICC-ME criteria may represent a more severely affected group, which has important implications for how patients are identified, treated, and included in research studies. The results highlight the need for standardized diagnostic criteria to ensure consistency in patient care and research.
This study does not prove that ME/CFS and chronic fatigue syndrome are definitively separate illnesses; it only shows that different diagnostic criteria identify patients with different severity levels. The observational design cannot establish whether the differences in severity are inherent to the conditions themselves or simply reflect how broadly each set of criteria casts its diagnostic net. It does not determine whether one set of criteria is more medically accurate than the other.
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, Sunnquist, Madison, Brown, Abigail, Evans, Meredyth, & Newton, Julia L (2016). Are Myalgic Encephalomyelitis and chronic fatigue syndrome different illnesses? A preliminary analysis.. Journal of health psychology. https://doi.org/10.1177/1359105313520335
BibTeX
@article{mecfsatlas-jason-2016-myalgic-encephalomyelitis,
author = {Jason, Leonard A and Sunnquist, Madison and Brown, Abigail and Evans, Meredyth and Newton, Julia L},
title = {Are Myalgic Encephalomyelitis and chronic fatigue syndrome different illnesses? A preliminary analysis.},
journal = {Journal of health psychology},
year = {2016},
doi = {10.1177/1359105313520335},
note = {PubMed: 24510231},
url = {https://www.mecfsatlas.com/evidence/jason-2016-myalgic-encephalomyelitis},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/jason-2016-myalgic-encephalomyelitis
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