MacHale, S M, Cavanagh, J T, Bennie, J et al. · Neuropsychobiology · 1998 · DOI
This study measured stress hormone (cortisol) levels in 30 ME/CFS patients and 15 healthy controls at different times of day. The researchers found that while individual cortisol measurements were similar between groups, ME/CFS patients showed a flattened pattern—their cortisol levels didn't drop as much in the evening as they should. Higher evening cortisol levels were connected to worse overall health and physical functioning in ME/CFS patients.
Understanding hormone dysfunction in ME/CFS may help explain fatigue and functional impairment. This study identifies a specific, measurable abnormality in the body's stress response system that correlates with disability severity, potentially opening avenues for diagnostic biomarkers and targeted treatments.
This study does not prove that abnormal cortisol patterns cause ME/CFS symptoms or disability—correlation does not equal causation. The cross-sectional design cannot determine whether hormone changes precede illness onset or result from prolonged illness. The sample size (30 patients) is relatively small, and findings may not generalize to all ME/CFS populations.
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
MacHale, S M, Cavanagh, J T, Bennie, J, Carroll, S, Goodwin, G M, & Lawrie, S M (1998). Diurnal variation of adrenocortical activity in chronic fatigue syndrome.. Neuropsychobiology. https://doi.org/10.1159/000026543
BibTeX
@article{mecfsatlas-machale-1998-diurnal-variation,
author = {MacHale, S M and Cavanagh, J T and Bennie, J and Carroll, S and Goodwin, G M and Lawrie, S M},
title = {Diurnal variation of adrenocortical activity in chronic fatigue syndrome.},
journal = {Neuropsychobiology},
year = {1998},
doi = {10.1159/000026543},
note = {PubMed: 9813459},
url = {https://www.mecfsatlas.com/evidence/machale-1998-diurnal-variation},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/machale-1998-diurnal-variation
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