Predicting therapeutic response to secondary treatment with bupropion: Dichotic listening tests of functional brain asymmetry

Studies using neuroimaging, electrophysiologic and cognitive measures have raised hopes for developing predictors of therapeutic response to antidepressants. Pretreatment measures of functional brain asymmetry have been found to be related to response to the selective serotonin reuptake inhibitor fluoxetine. This report examines the extent to which dichotic listening tests also predict clinical response to an antidepressant with a different mechanism of action, i.e., bupropion. Dichotic listening data were obtained for 17 unmedicated depressed patients who were subsequently treated with bupropion. Right-handed outpatients were tested on dichotic fused-words and complex-tones tests. Seven patients who responded to bupropion and 10 nonresponders did not differ in gender, age or education. Bupropion responders had significantly larger left-hemisphere advantage for perceiving words when compared to nonresponders, but there was no difference in their right-hemisphere advantage for tones. All patients having a left-hemisphere advantage above the normal mean responded to bupropion, whereas only 9% of patients below the normal mean responded to treatment. These findings should encourage further study of the clinical value of dichotic listening and other measures of functional brain asymmetry for identifying depressed patients who most benefit from treatment with different classes of antidepressants.