Chronic fatigue syndrome and depression: cause, effect, or covariate.
Abbey, S E, Garfinkel, P E · Reviews of infectious diseases · 1991 · DOI
Quick Summary
Many people with ME/CFS experience depression, but it's unclear why. This review examines four possible explanations: depression might be the main illness with fatigue as a symptom, depression might develop because of having ME/CFS, both conditions might occur together separately, or depression might be incorrectly diagnosed. The authors discuss how depression can affect medical tests used to study ME/CFS, which is important to understand when interpreting research results.
Why It Matters
Understanding whether depression causes ME/CFS, results from it, or exists separately is crucial for accurate diagnosis and appropriate treatment. This analysis helps patients and clinicians recognize that depression in ME/CFS may have different origins, and helps researchers design better studies by accounting for depression's potential effects on test results.
Observed Findings
Depressed mood and major depressive episode diagnoses are common in CFS patient populations
Depression can confound interpretation of immune function test results in CFS research
Depression affects performance on neuropsychological testing in ways that may complicate CFS diagnosis
Four plausible models exist to explain the CFS-depression relationship, each with some supporting evidence
Current diagnostic criteria may not adequately distinguish between CFS with secondary depression and primary depression presenting with fatigue
Inferred Conclusions
The relationship between CFS and depression is multifactorial and likely cannot be explained by a single model
Depression must be carefully controlled for or stratified in research studies to avoid confounding results of immune and cognitive testing
Future CFS research requires more rigorous methods to distinguish depression as primary, secondary, covariate, or artifact
Clinical assessment of CFS patients must consider the possibility of multiple concurrent conditions rather than assuming depression explains all symptoms
Remaining Questions
Which of the four models best explains the CFS-depression relationship in different patient subgroups?
What This Study Does Not Prove
This review does not prove which model is correct—it examines the evidence for each without definitive resolution. It does not establish causality between depression and ME/CFS, only describes possible relationships. The paper cannot determine whether depression screening practices are accurate or whether current diagnostic criteria adequately distinguish these conditions.