Electrodermal activity in depressive patients in remission and in matched healthy subjects.

Electrodermal activity (EDA) was investigated in 28 patients when depressive and when in remission and in 28 matched and 59 unmatched healthy subjects. The follow-up period ranged from 3 to 37 months (median two years). All the EDA variables were significantly elevated at follow-up and did not differ significantly from the EDA of the matched healthy subjects. However, in patients with extremely low electrodermal responsivity (EDR) when depressed, including suicide attempters, EDA was significantly elevated, but did not reach the levels of the healthy subjects, except for one EDA variable. Further, patients with major depressive episode and a history of recurrent depression did not reach the EDR levels found in the healthy subjects. The results are interpreted as an indication that normalization of EDA does not parallel clinical recovery and may be extended for several months (perhaps years for the EDR), possibly indicating vulnerability to relapse. The data may also be interpreted that persons who are normally electrodermally hyporesponsive, may, when depressive, develop a state of extreme hyporesponsivity that seems to be linked to the ability to carry out a suicide attempt.