Mckay, Pamela G, Martin, Colin R, Walker, Helen et al. · British journal of pain · 2021 · DOI
This study compared people with ME/CFS and fibromyalgia (FM) to see if these two conditions share similar symptoms and severity. Researchers asked 208 participants from each group to complete questionnaires about their pain, fatigue, sleep quality, mood, and how much these symptoms affected their daily lives. The study found that both groups experienced similarly debilitating symptoms and poor quality of life, suggesting these conditions may be connected in important ways.
Understanding the overlap between ME/CFS and fibromyalgia could improve clinical recognition, diagnosis, and treatment strategies for patients who experience overlapping symptoms. This research supports the need for integrated diagnostic and therapeutic approaches rather than managing these conditions in isolation.
This study does not prove that ME/CFS and FM are the same condition or that one causes the other—it only shows they share similar symptoms and severity. The cross-sectional design cannot establish temporal relationships or determine whether symptom overlap reflects shared biological mechanisms or common environmental/psychosocial factors. Internet-based recruitment may introduce selection bias, potentially overrepresenting more severely affected or digitally engaged patients.
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
Mckay, Pamela G, Martin, Colin R, Walker, Helen, & Fleming, Mick (2021). Chronic fatigue syndrome (CFS)/Myalgic Encephalomyelitis (ME) and Fibromyalgia (FM): the foundation of a relationship.. British journal of pain. https://doi.org/10.1177/2049463719875164
BibTeX
@article{mecfsatlas-mckay-2021-chronic-fatigue,
author = {Mckay, Pamela G and Martin, Colin R and Walker, Helen and Fleming, Mick},
title = {Chronic fatigue syndrome (CFS)/Myalgic Encephalomyelitis (ME) and Fibromyalgia (FM): the foundation of a relationship.},
journal = {British journal of pain},
year = {2021},
doi = {10.1177/2049463719875164},
note = {PubMed: 33633851},
url = {https://www.mecfsatlas.com/evidence/mckay-2021-chronic-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/mckay-2021-chronic-fatigue
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