Quantitative assessment of dynamic electroencephalogram (EEG) organizationas a tool for subtyping depressive syndromes

Up until now, no subclassification of affective psychoses has been validate d biologically. This follows unavoidably from a research practice of defini ng diagnostic subtypes in consensus conferences and only thereafter allowin g their validation. There is evidence that electroencephalograms (EEG) may be a useful tool in psychiatry, provided that the relevant information is e xtracted. Our EEG quantification procedure aims at an assessment of both the amount a nd range of variation of spontaneous changes of topographical alpha-power d istribution, developing within a certain period of recording under resting conditions. Our measures were designed to characterize the dynamic organiza tion of the EEG. This is quite obviously an eyeball evaluation but it has n evertheless been neglected in research. The study design was done retrospec tively. Included were inpatients with a primary depressive disorder. Main e xclusion criteria were an age older than 62 years and psychotropic drugs ot her than antidepressants. The psychopathology and other clinical data were routinely assessed within three days after admission by the AMDP documentat ion. An EEG was also routinely performed at admission. We made use of robus t, generally known non-parametric statistics. Those patients who exhibited a dynamically rigid EEG are especially prone t o recurrences, have a relative late onset of their illness, and show an acu te symptomatology characterized by organic-like features. The findings lend support to our contention that the quantitative assessmen t of the dynamics of the EEG-Gestalt allows the delimitation of a clinicall y important subtype that is characterized both cross-sectionally and in lon g-term respects. (C) 1999 Elsevier, Paris.