Suicidal behaviour and electrodermal activity in depressive inpatients.

Within the context of a habituation experiment, the electrodermal activity (EDA) of suicidal depressed patients was measured. Twenty-four patients had a suicide attempt in their most recent history; these attempts were divided into attempts with violent or nonviolent methods. All the patients who had used a violent method habituated quickly, as was the case for 4 of 5 patients who committed suicide in the year following the experiment. Just as many patients who used nonviolent methods habituated quickly or slowly. There was no indication that age, sex or medication had any influence. For 18 of these 24 patients, comparable groups, in terms of age and sex distribution, were formed containing either nonsuicidal depressed patients or patients with suicidal thoughts. No differences between groups concerning any of the EDA variables could be found. In accordance with these results, EDA cannot be considered to be a valid predictor for suicide-proneness. The relations between violent suicide attempts and nonreactivity should, however, be further examined and the group of nonreactive patients in EDA should be treated as a risk group for clinical reasons.