Cao, Yin, Li, Qinglin · Neuroreport · 2017 · DOI
This study compared how serotonin (a brain chemical linked to mood and energy) works differently in two types of animal models—one mimicking stress-related depression and another mimicking ME/CFS. Surprisingly, the two conditions showed opposite patterns: the stress model had low serotonin levels, while the fatigue model had high serotonin levels, suggesting these conditions may involve different biological mechanisms even though both cause low activity and mood problems.
Understanding how the serotonin system differs between ME/CFS and other conditions like depression could help researchers develop more targeted treatments and better distinguish ME/CFS from mood disorders in diagnosis and treatment planning. This study suggests ME/CFS may involve fundamentally different brain chemistry than stress-related illness, which could change how clinicians approach patient care.
This study does not prove that these findings apply to humans with ME/CFS—animal models have significant limitations and may not replicate human disease. The study shows correlations between serotonin levels and fatigue behavior, but does not establish whether altered serotonin causes the fatigue or is simply a consequence of it. Additionally, these results do not indicate whether targeting serotonin would be an effective treatment for ME/CFS 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
Cao, Yin & Li, Qinglin (2017). The variation of the 5-hydroxytryptamine system between chronic unpredictable mild stress rats and chronic fatigue syndrome rats induced by forced treadmill running.. Neuroreport. https://doi.org/10.1097/WNR.0000000000000797
BibTeX
@article{mecfsatlas-cao-2017-variation-hydroxytryptamine,
author = {Cao, Yin and Li, Qinglin},
title = {The variation of the 5-hydroxytryptamine system between chronic unpredictable mild stress rats and chronic fatigue syndrome rats induced by forced treadmill running.},
journal = {Neuroreport},
year = {2017},
doi = {10.1097/WNR.0000000000000797},
note = {PubMed: 28505018},
url = {https://www.mecfsatlas.com/evidence/cao-2017-variation-hydroxytryptamine},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/cao-2017-variation-hydroxytryptamine
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