DICHOTIC-LISTENING BEFORE AND AFTER FLUOXETINE TREATMENT FOR MAJOR DEPRESSION - RELATIONS OF LATERALITY TO THERAPEUTIC RESPONSE

Despite the wide variance in therapeutic response to antidepressants, there are few clinical or biological predictors of treatment outcome. Studies have suggested the possible value of dichotic listening measur es of perceptual asymmetry (PA) as predictors of treatment response. T his study examined the relation between outcome of fluoxetine treatmen t and performance on verbal and nonverbal dichotic tests. As part of a multisite study, 86 outpatients with major depression were tested on dichotic fixed-words and complex-tones tests both before and during tr eatment. Fluoxetine responders differed from nonresponders in having g reater right-ear (left-hemisphere) advantage for dichotic words and le ss left-ear (right-hemisphere) advantage for complex tones. There was no change in PA during fluoxetine treatment, which indicates that PA d ifferences between treatment responders and nonresponders are stable ( trait) characteristics. An aggregate, characteristic PA measure was th e best predictor of responder status in a logistic regression analysis . Findings from two clinical centers support the hypothesis that a cha racteristic tendency for relatively greater left- than right-hemispher e activation during dichotic listening is associated with better outco me of fluoxetine treatment.