Relationships between EEG and clinical characteristics in major depressive disorder.

Twenty-five patients with major depressive disorder (MDD) according to RDC were examined with computerized EEG before antidepressive treatment was initiated. Relationships between EEG parameters and clinical characteristics were studied. Age and pharmacological treatment were taken into account. Primary MDD was associated with an increase of delta amplitude. Retarded MDD was associated with an increase of delta and theta amplitudes and EEG variability. Recurrent unipolar MDD was related to a decrease of total alpha symmetry. Thus, subdiagnoses according to RDC were validated. The anxiety subsyndrome and to some extent vital symptoms, depressed mood, and CPRS total sum, were associated with asymmetry of the EEG pattern, whereas retardation was not. The number of former depressive episodes was positively correlated to amplitude of beta activity and negatively correlated to symmetry of EEG in the delta frequency band.