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

Gerard E. Bruder^a,b, Jonathan W. Stewart^b,c, Craig E. Tenke^a, Patrick J. McGrath^b,c, Paul Leite^a, Nil Bhattacharya^a, and Frederic M. Quitkin^b,c

^a Department of Biopsychology, New York State Psychiatric Institute, 1051 Riverside Drive, New York, NY 10032, USA 
^b Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA 
^c Depression Evaluation Service, New York State Psychiatric Institute, New York, NY, USA

Received 11 January 2000; revised 20 July 2000; accepted 20 July 2000

Abstract

Background: Recent reports suggest the value of electroencephalographic (EEG) and dichotic listening measures as predictors of response to antidepressants. This study examines the potential of EEG alpha asymmetry and dichotic measures of perceptual asymmetry as predictors of clinical response to 12 weeks of treatment with fluoxetine (Prozac).
Methods: Resting EEG (eyes open and eyes closed) and dichotic listening with word or complex tone stimuli were assessed in depressed 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. They also differed in their resting EEG alpha asymmetry, particularly in the eyes open condition. Nonresponders showed an alpha asymmetry indicative of overall greater activation of right than left hemisphere, whereas responders did not. The relationship between hemispheric asymmetry and treatment response interacted with gender, being evident among depressed women but not men.
Conclusions: The results are consistent with the hypothesis that a characteristic tendency toward greater left than right hemisphere activation is associated with favorable response to fluoxetine, whereas the opposite hemispheric asymmetry predicts poor response.