Meeus, Mira, Ickmans, Kelly, De Clerck, Luc S et al. · In vivo (Athens, Greece) · 2011
Researchers wanted to test whether a medication called citalopram (which affects serotonin, a brain chemical) could help reduce pain during exercise in people with ME/CFS and fibromyalgia. However, the study had to stop early because participants experienced significant side effects from the medication and one person with ME/CFS developed severe post-exertional malaise (worsening of symptoms after activity). Because of these problems, the researchers couldn't complete the study or reach any conclusions about whether the treatment worked.
This study highlights the challenges of conducting exercise-based research in ME/CFS populations, particularly the risk of post-exertional malaise and medication side effects. Understanding why this research was halted provides important context for designing safer future studies examining pain mechanisms in ME/CFS.
This study does not establish whether serotonergic pathways are or are not involved in pain regulation during exercise in ME/CFS, as it was terminated before data analysis. It does not prove that intravenous citalopram is ineffective or unsafe generally—only that it produced unexpected severe side effects in this small sample. No conclusions can be drawn about differences between ME/CFS, RA, and healthy controls.
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
Meeus, Mira, Ickmans, Kelly, De Clerck, Luc S, Moorkens, Greta, Hans, Guy, Grosemans, Sofie, et al. (2011). Serotonergic descending inhibition in chronic pain: design, preliminary results and early cessation of a randomized controlled trial.. In vivo (Athens, Greece). https://pubmed.ncbi.nlm.nih.gov/22021700/
BibTeX
@article{mecfsatlas-meeus-2011-serotonergic-descending,
author = {Meeus, Mira and Ickmans, Kelly and De Clerck, Luc S and Moorkens, Greta and Hans, Guy and Grosemans, Sofie and Nijs, Jo},
title = {Serotonergic descending inhibition in chronic pain: design, preliminary results and early cessation of a randomized controlled trial.},
journal = {In vivo (Athens, Greece)},
year = {2011},
note = {PubMed: 22021700},
url = {https://www.mecfsatlas.com/evidence/meeus-2011-serotonergic-descending},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/meeus-2011-serotonergic-descending
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