Parker, A J, Wessely, S, Cleare, A J · Psychological medicine · 2001 · DOI
This review examined how hormones and brain chemicals differ in ME/CFS patients. Researchers found that some patients have lower stress hormone (cortisol) levels, and their bodies show unusual patterns in serotonin and other brain chemical systems when tested. However, the findings were inconsistent across studies, and it's still unclear whether these changes cause ME/CFS symptoms or result from living with the illness.
This systematic review consolidates evidence that ME/CFS involves measurable biological changes in hormone and neurotransmitter systems, supporting the view that the condition has physiological mechanisms. Understanding these neuroendocrine patterns may help guide future research and validate patients' experiences of fatigue and other symptoms.
This review does not establish whether neuroendocrine abnormalities are the primary cause of ME/CFS or secondary consequences of the illness. It also does not clarify how specific hormonal or neurotransmitter changes translate into experienced symptoms, nor does it prove causation—only that associations exist.
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
Parker, A J, Wessely, S, & Cleare, A J (2001). The neuroendocrinology of chronic fatigue syndrome and fibromyalgia.. Psychological medicine. https://doi.org/10.1017/s0033291701004664
BibTeX
@article{mecfsatlas-parker-2001-neuroendocrinology-chronic,
author = {Parker, A J and Wessely, S and Cleare, A J},
title = {The neuroendocrinology of chronic fatigue syndrome and fibromyalgia.},
journal = {Psychological medicine},
year = {2001},
doi = {10.1017/s0033291701004664},
note = {PubMed: 11722149},
url = {https://www.mecfsatlas.com/evidence/parker-2001-neuroendocrinology-chronic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/parker-2001-neuroendocrinology-chronic
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