Divided attention in major depression

Depressive illness has been reported to interfere with effortful processing , which requires conscious attention. The aim of this study was to evaluate divided attention in depressed patients, as a function of the degree of di fficulty of the task performed. Tasks designed to measure unimodal and bimo dal reaction times were presented to 10 patients with major depression and 10 normal control subjects. Performance was evaluated both before treatment when the patients were depressed and after treatment when they had recover ed. Unlike the unimodal trials, the bimodal reaction time tasks were design ed to evaluate decision-making under conditions in which attention was divi ded between two perceptual channels. Reaction times were measured under two different conditions in order to assess the extent of the response delay i nduced by divided attention, modality shifting, and decision processing. Du ring simple response tasks, the depressed patients displayed significantly greater lengthening of reaction times when their attention was divided betw een two perceptual channels. This cross-modal delay effect occurred both fo r stimuli of the same modality and when shifting between modalities. The cr oss-modal delay effect was evident only for the choice tests in both the de pressed and the recovered patients, but only the recovered patients were as accurate as the control subjects. These results suggest that the need for decision processing in depressed patients results in a failure to allocate the mental resources required to complete interchannel shifting, when atten tion is divided between two perceptual channels. These data are consistent with the hypothesis that attentional regulation is impaired in major depres sion. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.