Urinary free cortisol excretion in chronic fatigue syndrome, major depression and in healthy volunteers.
Scott, L V, Dinan, T G · Journal of affective disorders · 1998 · DOI
Quick Summary
This study measured a stress hormone called cortisol in urine samples from people with ME/CFS, people with depression, and healthy individuals. The researchers found that people with ME/CFS had lower cortisol levels than healthy people, while people with depression had higher levels. This suggests that ME/CFS and depression affect the body's stress response system in opposite ways.
Why It Matters
This study provides biological evidence that ME/CFS involves a different mechanism than depression, despite overlapping symptoms like fatigue and low mood. Understanding that ME/CFS involves HPA axis hypoactivity (low cortisol) rather than hyperactivity may help guide more targeted treatment approaches and validates ME/CFS as a distinct condition from depression.
Observed Findings
CFS patients had significantly lower urinary free cortisol excretion compared to healthy controls.
Depressive patients had significantly higher urinary free cortisol excretion compared to healthy controls.
Five CFS patients with comorbid depression maintained the low cortisol profile of CFS-only patients, not the high profile seen in depression alone.
The HPA axis appears to function in opposite directions in CFS versus major depression.
Inferred Conclusions
ME/CFS involves hypoactivity of the hypothalamic-pituitary-adrenal axis, contrasting with the hyperactivity seen in depression.
Depressive symptoms in ME/CFS may arise from different biological mechanisms than primary major depression.
Low cortisol excretion may be a biological marker distinguishing ME/CFS from depression.
Remaining Questions
What causes the HPA axis to become underactive specifically in ME/CFS?
Does low cortisol contribute to symptoms, or is it a consequence of other disease processes?
How do these cortisol findings relate to other immune and metabolic abnormalities reported in ME/CFS?
What This Study Does Not Prove
This study does not prove that low cortisol causes ME/CFS symptoms, only that an association exists. It cannot explain why the HPA axis becomes underactive in ME/CFS or whether this is a primary cause or secondary consequence of the illness. The small sample size and cross-sectional design limit generalizability and cannot establish causality.
Tags
Symptom:Fatigue
Biomarker:Blood Biomarker
Method Flag:Weak Case DefinitionSmall SampleExploratory Only