Objective: To examine neuropsychological deficits in unmedicated patients with a nonpsychotic unipolar major depressive disorder.
Background: Although cognitive deficits in depression have been reported in several studies, most previous studies have concentrated on a few areas of cognition in more or less heterogenous groups of depressives.
Method: Twenty-two nonhospitalized patients with a DSM-III-R defined nonpsychotic unipolar major depressive disorder were compared with 30 healthy controls. Neuropsychological tests were organized in the following functions: motor function, selective attention, mental flexibility, visuomotor tracking, working memory, short-term memory, verbal long-term memory, nonverbal long-term memory, verbal fluency, and visuospatial function.
Results: There emerged an overall group difference in neuropsychological test performance, with patients scoring significantly lower than controls. Bonferroni corrected univariate analyses of variance showed that patients performed significantly below controls in the following areas: selective attention, working memory, verbal long-term memory, and verbal fluency. Two functions were areas of differential deficits in the depressed group: selective attention and working memory. Impaired verbal long-term memory seemed to reflect an underlying working memory deficit.
Conclusions: Nonhospitalized patients with a nonpsychotic unipolar major depressive disorder exhibited an overall neuropsychological deficit and they performed disproportionately worse in the two domains of selective attention and working memory. The neurobiological implications of the present results are in accordance with the hypothesis that there is a global-diffuse impairment of brain function with particular involvement of the frontal lobes in nonpsychotic unipolar major depressive disorder.