Electrodermal activity among subtypes of depression.

To determine whether subgroups of depressed patients could be differentiated on the basis of electrodermal activity (EDA), the skin conductance of 36 depressed patients was recorded for two experimental conditions. In the first condition, subjects heard 10 85-dB tones after receiving instructions that were intended to relax the patients. In the second experimental condition, subjects heard 12 105-dB tones, one-half of which were signal tones containing a brief gap in the middle. The subjects were required to respond to the tones containing the gap by pressing a foot pedal. No differences in tonic or phasic EDA were detected on the basis of unipolar or bipolar subtype, response to the dexamethasone suppression test, severity of depression, medication status, or sex. However, patients who exhibited features of psychomotor retardation had significantly lower levels of tonic EDA than did their nonretarded counterparts. The EDA of the depressed patients as a group was uniformly low. These results are consistent with other reports indicating that, with the exception of the retarded/nonretarded distinction, there are no differences in EDA among the various subtypes of depression.