β-endorphin concentrations are decreased in peripheral blood mononuclear cells of chronic fatigue syndrome patients:: Comparison with depression

Chronic Fatigue Syndrome [CFS] has uncertain etiology, and diagnosis overlaps with depression. Since most studies suggest an activation of immune responses in CFS, and the opioid peptide beta-endorphin [BE] content in peripheral blood mononuclear cells BE was shown to be decreased when the immune system is activated, and increased when it is depressed, it seemed worthwhile to investigate whether BE concentrations in peripheral blood mononuclear cells differed in CFS and depressed patients. P-Endorphin concentrations were measured by radioimmunoassay in peripheral blood mononuclear cells obtained from 24 CFS and six depressed patients, and 16 controls. The data obtained indicate that BE concentrations are decreased in CFS patients when compared with depressed patients and controls. In conclusion, peripheral blood mononuclear cells BE concentrations could be an useful instrument in the differential diagnosis between CFS and depression.