Electrodermal activity in suicidal and nonsuicidal depressive patients and in matched healthy subjects.

The electrodermal activity (EDA) was measured in 25 suicidal and 34 nonsuicidal depressive patients and 59 individually matched healthy subjects during stimulation with neutral tone stimuli. Suicidal behaviour, especially the occurrence of attempts, was related to low electrodermal responsivity (EDR) and low stimulus-unrelated phasic activity, but unrelated to tonic EDA. The EDR of different groups of subjects was successfully illustrated and tested by statistical methods known as survival statistics. The extreme hyporesponsivity in the attempters was observed irrespective of whether the attempt had been made previously or during the current depression. Electrodermal hyporesponsivity among depressive patients may be a part of a mechanism operating in the suicidal process, and an expression for a factor related to the ability to carry out a suicide attempt. This nonverbal and noninvasive method may yield additional valuable information when estimating the suicide risk in depressive patients in clinical work.