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An investigation of some neuropsychological, cognitive and behavioral aspects of depression Johnson, Olive Skene

Abstract

The purpose of this study was to evaluate Tucker's hypothesis of differential hemispheric functioning in depression, the validity of Beck's cognitive theory and Lewinsohn's behavioral theory of depression for clinically depressed subjects, and the relationship between hemispheric functioning and cognitive-behavioral functioning throughout a period of hospitalization for depression. A 3x2x2x3 repeated-measures study was conducted with 48 right-handed subjects in three groups: depressed, normal and psychiatric comparison. Each group contained an equal number of males and females. To test for right hemisphere functioning, subjects were administered a dichotic stimulation test (Musical Chords) in which the left ear (right hemisphere) has previously proven superior in normal right-handers. A dichotic test in which the right ear is normally superior (Word Triads) was administered as a control. A righthemrsphere cognitive test (Flags) was also administered, with a left hemisphere cognitive test (Word Fluency) as a control. A Cognitive Distortion Questionnaire was used to measure depressives' cognitions within Beck's typology, and a short version of the Pleasant Events Schedule was used to measure response-contingent positive reinforcement within Lewinsohn's theoretical framework. Patients were tested at admission to hospital, 10-13 days later, and at discharge, in order to observe changes in hemispheric, cognitive and behavioral functioning, at intervals ranging from severe depression to recovery. On both dichotic tests, depressives failed to obtain normal ear superiorities at admission to hospital, but did so by discharge. Flags scores of depressives were low at each trial, while Word Fluency was unimpaired at any time. These results suggest that two different processes, one acute and one chronic, are operating during depression. An acute interhemispheric process apparently affects both hemispheres, producing a breakdown in normal asymmetries for processing mode. With treatment, this acute process abates, and normal asymmetries once again emerge. A second process apparently involves chronic inhibition of certain right hemisphere cognitive functions. This could represent a neurogenic index of psychiatric vulnerability within depression-prone individuals. Consistent with Beck's cognitive theory, depressives demonstrated a high degree of cognitive distortion at admission to hospital. However, since at discharge depressives no longer demonstrated cognitive distortion, the study provided no evidence that cognitive distortion is a characteristic of depression-prone persons. However, more research is needed to assess the validity of the cognitive distortion measure employed in the study. Consistent with Lewinsohn's behavioral theory, depressives demonstrated a low rate of response-contingent positive reinforcement at admission to hospital and increased reinforcement rate by discharge. However, since reinforcement rate of normals dropped across trials while their mood level did not, these results do not provide clear support for Lewinsohn's theory. No significant relationship was found between changes in hemispheric' functioning and changes in either cognitive distortion or reinforcement rate. No sex differences were found in any of the variables under consideration. The necessity for using multiple measures of hemispheric functioning is discussed, and suggestions for future research are proposed.

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