Pain thresholds during and after treatment of severe depression with electroconvulsive therapy

Pain and depression are often associated suggesting that both conditions share a common neurobiological mechanism, which modulate emotional function and processing of noxious information. Pain thresholds are hypothesized to be altered in depressed patients and normalized with the amelioration of depression. The purpose of this study was therefore to determine pain thresholds in patients during and after treatment with electroconvulsive therapy (ECT) of severe depression and in healthy controls. Seventeen depressed patients (Hamilton depression score > 18) and an age and gender matched control group of same size participated in the study. Pain detection and tolerance thresholds to pressure and pain tolerance thresholds to the Cold Pressor Test by exposure to ice-water was measured twice in depressed patients during and after ECT and twice in controls with a similar time interval. While ECT significantly improved Hamilton depression score (from mean 23.9 (SD:5) to mean 12.5 (SD:5.7)) there was no significant change in pain thresholds during and after ECT in the patient group. However, depressed patients had significantly lower pain tolerance in the Cold Pressor Test on both examinations and on pressure pain tolerance on the second examination day than their corresponding control subjects. The differential effect of ECT on depression score and pain processing indicate that mood and noxious processing are not medicated directly by the same systems but that a complex relationship between pain and depression exists.