Baraniuk, James N · International journal of molecular sciences · 2025 · DOI
This study examined fluid from around the brain and spinal cord in ME/CFS patients and healthy controls, measuring chemical substances before and after exercise. Researchers found that ME/CFS patients have abnormal levels of certain chemicals related to energy production and brain function, especially after exercise. The study suggests that exercise may trigger harmful changes in brain chemistry in ME/CFS patients that don't happen in healthy people, which could explain post-exertional malaise (the worsening of symptoms after activity).
This is the first study to use CSF analysis to directly examine brain-level metabolic changes associated with post-exertional malaise, providing objective biological evidence for a hallmark symptom of ME/CFS. The identification of specific metabolic pathways—particularly folate and one-carbon metabolism—offers potential targets for diagnostic testing and future treatments. Understanding what happens in the brain during PEM is critical to validating ME/CFS as a biological disease.
This study demonstrates association and correlation in CSF metabolites but does not prove causation—abnormal metabolites may be consequences rather than causes of ME/CFS. The findings are mechanistic observations in a small cohort and do not establish whether correcting these metabolic abnormalities would reverse symptoms or improve outcomes. The study also does not determine whether observed changes are specific to ME/CFS or occur in other post-viral conditions.
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 →
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