ME/CFS and Post-Exertional Malaise among Patients with Long COVID.

Jason, Leonard A, Dorri, Joseph A · Neurology international · 2022 · DOI

Quick Summary

Researchers studied 465 people with long-term COVID symptoms to see how many also had ME/CFS (a serious condition causing extreme fatigue and worsening after activity). They found that about 6 in 10 people with long COVID met the medical criteria for ME/CFS. Interestingly, some people thought they had ME/CFS when they didn't, while others had ME/CFS without realizing it—showing that self-diagnosis alone isn't reliable.

Why It Matters

This study quantifies the substantial overlap between Long COVID and ME/CFS, challenging the assumption that Long COVID and ME/CFS are entirely separate conditions. It demonstrates that objective diagnostic criteria are essential because patient self-report alone misses or over-identifies ME/CFS, which has implications for clinical recognition, patient support, and research stratification.

Observed Findings

58% of Long COVID patients met standardized ME/CFS case definitions
71% of patients self-reporting ME/CFS actually met diagnostic criteria
40% of patients who denied having ME/CFS nonetheless met diagnostic criteria
Mean symptom duration was 70.5 weeks post-COVID onset
Participants were predominantly white, female, and from North America

Inferred Conclusions

ME/CFS is highly prevalent among Long COVID populations
Self-reported ME/CFS diagnosis is unreliable; validated screening instruments are necessary for accurate case identification
Both under-diagnosis and over-diagnosis of ME/CFS occur in Long COVID cohorts
Long COVID and ME/CFS may represent overlapping or related clinical entities

Remaining Questions

What biological mechanisms explain the overlap between Long COVID and ME/CFS?
Does the prevalence of ME/CFS among Long COVID patients differ by demographic factors, COVID severity, or time since infection?
Can longitudinal follow-up clarify whether ME/CFS emerges during Long COVID or predates it?
How do ME/CFS diagnostic criteria need to be refined to improve detection accuracy in post-viral illness populations?

What This Study Does Not Prove

This study does not prove that Long COVID causes ME/CFS or establish the mechanistic relationship between them—it only documents their co-occurrence at one time point. The cross-sectional design cannot determine whether ME/CFS develops during Long COVID or represents a pre-existing condition, nor does it clarify whether they share identical biological pathways.

Topics

Long COVID Overlap Post-Exertional Malaise

Metadata

DOI: 10.3390/neurolint15010001
PMID: 36648965
Review status: Machine draft
Evidence level: Single-study or moderate support from human research
Last updated: 7 April 2026