Electroencephalographic and perceptual asymmetry differences between responders and nonresponders to an SSRI antidepressant

Background: Recent reports suggest the value of electroencephalographic and dichotic listening measures as predictors of response to antidepressants. This study examines the potential of electroencephalographic alpha asymmetr y and dichotic measures of perceptual assymmetry as predictors of clinical response to 12 weeks of treatment with fluoxetine (Prozac), Methods: Resting electroencephalography (eyes open and eyes closed) and dic hotic listening with word or complex tone stimuli were assessed in depresse d outpatients during a pretreatment period. Results: Fluoxetine responders (n = 34) differed from nonresponders (n = 19 ) in favoring left over right hemisphere processing of dichotic stimuli. Th ey also differed in their resting electroencephalographic alpha asymmetry, particularly, in the eyes open condition. Nonresponders showed an alpha asy mmetry indicative of overall greater activation of the right hemisphere tha n the left, whereas responders did not. The relationship between hemispheri c asymmetry and treatment response interacted with gender, being evident am ong depressed women but not men. Conclusions: The results are consistent with the hypothesis that a characte ristic tendency toward greater left than right hemisphere activation is ass ociated with favorable response to fluoxetine, whereas the opposite hemisph eric asymmetry predicts poor response. Biol Psychiatry 2001; 49:416-425 (C) 2001 Society of Biological Psychiatry.