Tak, Lineke M, Riese, Harriëtte, de Bock, Geertruida H et al. · Biological psychology · 2009 · DOI
This research review looked at whether people with ME/CFS and similar conditions have problems with their nervous system's ability to regulate heart rate. Researchers combined results from 23 studies involving 533 patients and found weak evidence that patients may have lower parasympathetic nerve activity (the calming part of the nervous system) compared to healthy people. However, the evidence was not strong enough to draw firm conclusions, and the studies reviewed had many quality problems that made the results unreliable.
Understanding whether autonomic nervous system dysfunction contributes to ME/CFS is crucial for identifying potential disease mechanisms and therapeutic targets. This comprehensive review reveals that while ANS abnormalities remain plausible in ME/CFS, the current research base is insufficient to confirm this hypothesis, highlighting the need for higher-quality investigations that could reshape clinical understanding and treatment approaches.
This review does not prove that autonomic dysfunction causes ME/CFS or that it is present in all patients; after accounting for publication bias, the overall evidence becomes statistically nonsignificant. The findings do not establish whether any observed ANS differences are a primary cause, a consequence of illness, or a secondary effect of reduced activity and deconditioning. The methodological limitations across studies mean the weak associations found may not reflect true biological relationships.
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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