Diagnosis and subtyping of depressive disorders by quantitative electroencephalography: III. Discriminating unipolar from bipolar depression.

One hundred fifty-two inpatient major depressives fulfilled the Research Diagnostic Criteria for unipolar (N = 111) or bipolar (N = 41) affective disorder. After at least seven days drug-free, all patients had a thyrotropin releasing hormone stimulation test (TRHST), a dexamethasone suppression test (DST) and quantitative electroencephalography (QEEG). Multivariate analysis of variance was used to compare post-dexamethasone cortisol, delta TSH, six regional QEEG measures of interhemispheric symmetry and six focal measures of QEEG frequency. Age, sex and diagnosis were included in the analysis. Unipolar depressives were discriminated from bipolar depressives by age, delta TSH and QEEG fast wave abnormalities in the alpha and beta frequency bands. Unipolar depressives were significantly older, had lower mean delta TSH, showed excessive alpha activity and deficient beta activity. Bipolar depressives were younger, had higher mean delta TSH, showed a deficit of alpha activity and excessive beta activity. Unipolar might be discriminable from bipolar major depression by the use of two objective procedures--TRHST and QEEG. The two disorders appear to be biochemical and electrophysiological opposites. Treatment implications are discussed.