Hemispheric asymmetry in depression and mania. A longitudinal QEEG study in bipolar disorder

Background: previous research has been inconclusive about the nature of hemispheric asymmetry in emotional processing. Method: 13 patients with DSM-IV bipolar disorder received repeated QEEGs over 2 years in different mood states. Z-score measures of asymmetry were assessed. Results: asymmetry in frontotemporal slow-wave activity appeared to be in opposite directions in depression compared to mania/hypomania. Conclusions: mood change in bipolar disorder is associated with change in QEEG asymmetry. Limitations: study of larger numbers of more homogenous patients under similar conditions is needed. Clinical relevance: study of mood state-dependent asymmetry changes in bipolar disorder may lead to better understanding of hemispheric processing of emotion.