E2 ModerateModerate confidencePEM unclearCross-SectionalPeer-reviewedMachine draft
Functioning in individuals with chronic fatigue syndrome: increased impairment with co-occurring multiple chemical sensitivity and fibromyalgia.
Brown, Molly M, Jason, Leonard A · Dynamic medicine : DM · 2007 · DOI
Quick Summary
This study looked at 114 people with ME/CFS to see how often they also had fibromyalgia or multiple chemical sensitivity, and whether having more than one condition made their symptoms worse. The researchers found that about 44% had ME/CFS alone, while others had it combined with one or both of the other conditions. People with all three conditions were the most disabled and had the hardest time with daily activities compared to those with ME/CFS alone.
Why It Matters
This study provides evidence that ME/CFS patients with co-occurring fibromyalgia and chemical sensitivity experience substantially greater disability than those with ME/CFS alone, validating the clinical experience of many patients with multiple diagnoses. Understanding this additive effect of comorbidities is important for treatment planning and rehabilitation strategies tailored to patients' actual burden of illness.
Observed Findings
- 43.9% of participants met criteria for CFS alone; 56.1% had CFS with co-occurring MCS and/or FM.
- The CFS-MCS-FM group reported significantly greater disability on measures of physical functioning, general health, and bodily pain compared to the CFS-alone group.
- In vivo physical measures did not differ significantly between groups, but the CFS-MCS-FM group rated their perceived exertion as higher than the CFS-alone group.
- Individuals with CFS alone showed the highest functioning across multiple domains including disability, depression, and symptom severity.
Inferred Conclusions
- Having more than one diagnosis (CFS with MCS and/or FM) substantially exacerbates disability beyond CFS alone.
- While these conditions frequently co-occur, they may represent distinct entities rather than manifestations of a single illness, as comorbidity had an additive effect on disability.
- The discrepancy between objective physical measures and subjective symptom ratings suggests that perception of exertion may be an important clinical marker in patients with multiple diagnoses.
Remaining Questions
- Why do MCS and FM co-occur so frequently with ME/CFS, and what underlying mechanisms drive this association?
- Does the order or timing of illness onset affect the severity of comorbid presentations, or progression over time?
What This Study Does Not Prove
This study does not prove that MCS and FM cause additional disability in ME/CFS, only that they are associated with worse outcomes. The cross-sectional design means we cannot determine whether having multiple conditions causes worse functioning, or whether more severe baseline illness predisposes people to additional diagnoses. The study also does not establish whether CFS, MCS, and FM are truly separate diseases or manifestations of one underlying condition.
Tags
Symptom:PainFatigueSensory Sensitivity
Method Flag:PEM Not DefinedSmall SampleMixed Cohort
Metadata
- DOI
- 10.1186/1476-5918-6-6
- PMID
- 17540028
- Review status
- Machine draft
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 8 April 2026
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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