Dynamically rigid EEG and subtyping of depressive syndromes

Abstract

SummaryThe contribution of EEG to theory as well as to psychiatric practice of depression is negligible. The prevailing view is that no ‘abnormal’ characteristic can be demonstrated in affective disorders. Since ‘abnormal’ is generally taken in a neurological sense, all those EEG characteristics are faded out which cannot be regarded as neurologically abnormal but which nevertheless may be useful for psychiatric concerns. Thus, early observations concerning the spatio-temporal aspect of the EEG have essentially gone unnoticed, thereby evading systematic scrutiny. It has been maintained that periodically melancholic patients more often exhibited a dynamically rigid EEG than patients with neurotic forms. Our retrospective study involved 314 inpatients with depressive disorders who were subdivided into an ‘endogenous’ and a ‘non-endogenous’ subgroup using both IC'D 9 diagnoses as well as RDC criteria. The EEGs were designated to one of the three categories, rigid, labile, or physiomorphic. Forty-two percent of the patients in the ‘endogenous’ subgroup exhibited a dynamically rigid EEG (DR) compared to 20% of those from the ‘non-endogenous’ subgroup. Symptoms of psychomotor retardation positively correlated with DR, whereas ‘anxiety’ positively correlated with non-DR (labile or physiomorphic EEG dynamics). In addition, there was a positive correlation between DR and both the number of manifestations of depressive disorders and the number of previous hospitalizations. We interpret DR as a personality-bound characteristic which, far from being pathognomonic of a certain syndrome or even diagnosis, instead indicates a higher degree of vulnerability towards manifestation of melancholic syndromes with psychomotor retardation. This does not exclude the possibility of a state-dependent intensification of DR.