Nakao, Mutsuhiro · Nihon rinsho. Japanese journal of clinical medicine · 2009
This review explores why people develop functional somatic syndromes—a group of conditions including ME/CFS, fibromyalgia, and irritable bowel syndrome that cause real suffering but don't show clear structural damage on standard tests. The authors suggest that mood, stress sensitivity, genetics, and environment all play important roles in these conditions, and that how patients interact with their doctors matters too.
This review helps contextualize ME/CFS within a broader framework of functional somatic syndromes, highlighting shared biological mechanisms (autonomic and HPA-axis dysfunction) and psychological factors that could guide research and treatment. Understanding these overlapping etiologies may help clinicians recognize common pathways and develop more targeted interventions for ME/CFS patients.
This review does not establish causation, only identifies associations and proposed mechanisms from existing literature. It does not provide direct experimental evidence specific to ME/CFS, nor does it distinguish which factors are primary drivers versus secondary consequences of illness. The review does not quantify the relative contribution of psychological versus biological factors.
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 →
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Primary citation
Nakao, Mutsuhiro (2009). [Etiology of functional somatic syndromes].. Nihon rinsho. Japanese journal of clinical medicine. https://pubmed.ncbi.nlm.nih.gov/19768898/
BibTeX
@article{mecfsatlas-nakao-2009-etiology-functional,
author = {Nakao, Mutsuhiro},
title = {[Etiology of functional somatic syndromes].},
journal = {Nihon rinsho. Japanese journal of clinical medicine},
year = {2009},
note = {PubMed: 19768898},
url = {https://www.mecfsatlas.com/evidence/nakao-2009-etiology-functional},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/nakao-2009-etiology-functional
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