E0 ConsensusModerate confidencePEM ?Systematic-ReviewPeer-reviewedMachine draft
Potential causal factors of CFS/ME: a concise and systematic scoping review of factors researched.
Muller, Ashley Elizabeth, Tveito, Kari, Bakken, Inger Johanne et al. · Journal of translational medicine · 2020 · DOI
Quick Summary
Researchers reviewed over 1,100 studies published between 1979 and 2019 to understand what might cause ME/CFS. They found that scientists have studied many different potential causes, including immune system problems, psychological factors, infections, and hormonal imbalances. However, most of these studies were small and only suggested ideas rather than proving what actually causes ME/CFS—we need larger, better-designed studies to get real answers.
Why It Matters
This comprehensive overview of the research landscape reveals that ME/CFS is being studied from multiple angles, which validates the complexity patients experience. However, it also highlights a critical gap: we lack large, well-designed studies that can definitively identify what causes ME/CFS, which is essential for developing better treatments and prevention strategies.
Observed Findings
- Immunological factors were examined in 297 studies, making them the most researched category of potential causes.
- Psychological factors were investigated in 243 studies, reflecting ongoing debate about psychological contributions.
- Infections and neuroendocrine factors were each studied in 198 studies, indicating balanced research interest.
- The majority of studies (>50%) included 100 or fewer participants, limiting statistical power.
- Case-control studies comparing ME/CFS patients to healthy controls were the dominant design (894 studies).
Inferred Conclusions
- No single factor dominates ME/CFS etiology; instead, the condition likely involves multiple interacting biological, psychological, and social factors.
- The current research literature is primarily hypothesis-generating rather than causal-establishing, requiring stronger methodological designs moving forward.
- Future research must prioritize larger sample sizes and more rigorous study designs to move beyond association-finding to actual causal determination.
Remaining Questions
- Which factors, if any, are sufficient or necessary to cause ME/CFS, and how do they interact?
- Why do most studies remain small and underpowered, and what barriers exist to conducting large, definitive causal studies?
What This Study Does Not Prove
This review does not establish which factors actually cause ME/CFS—it only maps what researchers have studied. The predominance of small case-control studies means most published work identifies associations rather than causal relationships. This scoping review itself cannot determine which hypotheses are correct or most important.
Tags
Symptom:Fatigue
Biomarker:CytokinesBlood Biomarker
Phenotype:Infection-Triggered
Method Flag:Weak Case DefinitionSmall SampleExploratory Only
Metadata
- DOI
- 10.1186/s12967-020-02665-6
- PMID
- 33317576
- Review status
- Machine draft
- Evidence level
- Established evidence from major reviews, guidelines, or evidence maps
- Last updated
- 8 April 2026