Hickie, Ian, Davenport, Tracey, Vernon, Suzanne D et al. · The Australian and New Zealand journal of psychiatry · 2009 · DOI
This large international study analyzed data from nearly 38,000 people across 21 countries to determine whether chronic fatigue and ME/CFS are real, recognizable conditions. Researchers found that people with these conditions share a consistent pattern of five main symptom types—muscle pain and fatigue, thinking difficulties, inflammation-related symptoms, sleep problems, and mood changes—regardless of where they live or which type of doctor they see. This consistency across different countries and healthcare settings provides strong evidence that chronic fatigue and ME/CFS are genuine medical conditions, not just psychiatric problems.
This study provides international evidence that ME/CFS and chronic fatigue are valid, recognizable medical conditions with consistent symptom patterns worldwide, countering historical dismissal of these conditions as purely psychiatric. Understanding that these illnesses have a consistent biological symptom structure across countries and healthcare settings strengthens advocacy for research funding and clinical recognition. The identification of five distinct symptom domains may help guide future diagnostic criteria and treatment development.
This study does not identify the biological or infectious causes of ME/CFS or explain why these symptom patterns occur. The cross-sectional design cannot establish whether symptom patterns change over disease course or predict treatment responses. It also does not prove that psychiatric factors are unimportant—only that ME/CFS cannot be defined solely as a psychiatric disorder.
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
Hickie, Ian, Davenport, Tracey, Vernon, Suzanne D, Nisenbaum, Rosane, Reeves, William C, Hadzi-Pavlovic, Dusan, et al. (2009). Are chronic fatigue and chronic fatigue syndrome valid clinical entities across countries and health-care settings?. The Australian and New Zealand journal of psychiatry. https://doi.org/10.1080/00048670802534432
BibTeX
@article{mecfsatlas-hickie-2009-chronic-fatigue,
author = {Hickie, Ian and Davenport, Tracey and Vernon, Suzanne D and Nisenbaum, Rosane and Reeves, William C and Hadzi-Pavlovic, Dusan and Lloyd, Andrew and International Chronic Fatigue Syndrome Study Group},
title = {Are chronic fatigue and chronic fatigue syndrome valid clinical entities across countries and health-care settings?},
journal = {The Australian and New Zealand journal of psychiatry},
year = {2009},
doi = {10.1080/00048670802534432},
note = {PubMed: 19085525},
url = {https://www.mecfsatlas.com/evidence/hickie-2009-chronic-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/hickie-2009-chronic-fatigue
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