Schondorf, R, Freeman, R · The American journal of the medical sciences · 1999 · DOI
This review examines how problems with standing up (orthostatic intolerance) are connected to ME/CFS. Many people with ME/CFS experience symptoms like dizziness, fatigue, trouble concentrating, shaking, and nausea when standing or sitting upright. The authors review what we know about this connection, including how to diagnose it, what tests can help, what might cause it, and how it might be treated.
Understanding the link between orthostatic intolerance and ME/CFS is important because orthostatic symptoms are commonly reported by patients and may represent a key mechanism underlying disability. Recognizing and properly diagnosing OI in ME/CFS could lead to better management strategies and improved quality of life for affected patients.
This review does not establish that orthostatic intolerance causes ME/CFS or vice versa—it documents an association. As a review article rather than original research, it does not present new experimental data or definitively prove any specific pathophysiological mechanism. It cannot determine whether OI is a core feature, a secondary consequence, or a comorbid condition in ME/CFS.
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
Schondorf, R & Freeman, R (1999). The importance of orthostatic intolerance in the chronic fatigue syndrome.. The American journal of the medical sciences. https://doi.org/10.1097/00000441-199902000-00006
BibTeX
@article{mecfsatlas-schondorf-1999-importance-orthostatic,
author = {Schondorf, R and Freeman, R},
title = {The importance of orthostatic intolerance in the chronic fatigue syndrome.},
journal = {The American journal of the medical sciences},
year = {1999},
doi = {10.1097/00000441-199902000-00006},
note = {PubMed: 10037115},
url = {https://www.mecfsatlas.com/evidence/schondorf-1999-importance-orthostatic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/schondorf-1999-importance-orthostatic
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