Skin Temperature, Conductance Differentiate Chronic Fatigue From Depression

NEW YORK (Reuters Health) Aug 31 - Chronic fatigue syndrome (CFS) and depression have distinct neurobiological properties, researchers in Canada report, suggesting that the two conditions have unique etiologies. Unlike depression, CFS is characterized by decreased skin conductance levels but increased peripheral skin temperature.

"Electrodermal analysis may represent a useful tool in the process of differential diagnosis of CFS and depression," Dr. Hannah Pazderka-Robinson and her colleagues suggest in their paper in the August issue of the International Journal of Psychophysiology.

The considerable overlap between the symptoms of CFS and of depression has led many to question whether CFS is really a different condition, or if it is actually a manifestation of depression. Dr. Pazderka-Robinson and her team at the University of Alberta, Edmonton, theorized that psychophysiological indicators could be used to discriminate between the two.

They obtained their data from 36 nondepressed subjects with CFS, 19 with depression and 33 normal, healthy controls. Bilateral electrodermal activity was recorded using electrodes placed on the third and fourth fingers of each hand, while skin temperature was measured with temperature transducers placed on the fifth finger.

Skin temperature levels differed significantly between the CFS group (mean 34.1 degrees C) versus the depression group (31.1 degrees) and the control group (30.1 degrees).

Mean tonic skin conductance levels were significantly lower in the CFS group compared with the control group and the depression group. The depression group and the control group did not differ significantly from each other with regard to this measurement, however.

"Both these findings point to down-regulation of autonomic sympathetic tone, as the sympathetic system is responsible for vasoconstriction in the periphery," Dr. Pazderka-Robinson and her associates conclude.

Int J Psychophysiol 2004;53:171-182.