Electrodermal activity in low back pain patients with and without co-morbid depression.

Electrodermal activity was examined at rest and during a series of pure innocuous tones in two groups of chronic low back pain patients, one of which consisted of patients suffering also from depression. A group of healthy participants and a group of patients suffering from depression unrelated to pain served as control groups. The non-depressed patients presented an increased electrodermal activity, especially a higher frequency of non-specific fluctuations, as compared to the three other groups. Skin conductance level also appeared lower in the two groups of depressed participants than in the healthy control group. These data show that the EDA recorded in chronic pain patients with and without co-morbid depression must advantageously be analysed separately.