ELECTROENCEPHALOGRAPHY IN PSYCHIATRY - A CRITICAL-EVALUATION

The ''Psychophysiology working group'' of AMDP (Arbeitskreis fur Metho dik und Dokumentation in der Psychiatrie) intends to establish, a broa d data base of EEG data in psychiatry. The purpose is to determine whe ther the EEG can contribute to the diagnostic classification of psychi atric disorders, to the description of the course of the illness and t o the prediction of the therapeutic outcome. Since several studies hav e shown promising results during the last years, members of the workin g group have investigated literature and written reviews which will be summarized in this con-tribution. This includes a critical evaluation of the cited studies. We restrict ourselves to schizophrenia, affecti ve and anxiety disorder. Out of more than 3000 available contributions in the world literature 500 have been evaluated by the group, and 216 are taken for this summary. The critical review is the basis for futu re research of the working group and gives the following working hypot heses: Under resting conditions anxiety does not show typical deviatio ns from normality. However, EEG-recordings under experimentally induce d anxiety do show typical changes: in normal persons there is usually an increase in desynchronous fast beta-activity (hyperarousal accompan ied by cognitive coping), whereas patients with anxiety disorder show hypersynchronized alpha-activity, as it is usually found in deep relax ation. Thus, hypersynchronized alpha-activity might be an expression o f a compensatory effort of the system to relax. Anxiolytics induce syn chronous beta- or sub-alpha activity, which may force the system into more rigid patterns (relaxation) and thus, could counteract anxiety in normal persons, if hyperarousal going along with desynchronisation is not sufficient. Furthermore, benzodiazepines show also an increase in desynchronous fast beta-activity which could be useful in chronic anx iety, in order to support cognitive efforts. While depressive disorder s cause a variety of changes in the wake EEG, that can only partly lin ked with the clinical picture (neurotic versus endogenous), the sleep EEG shows a decrease in REM-latency, an increase in REM density and a decrease in sleep efficiency in patients with depressive symptoms. How ever, nosological specifity is not established yet. Successful antidep ressive therapy counteracts these changes. The common feature in the w ake EEG is the interaction with vigilance dependent variables in both directions: stimulation and sedation. Schizophrenia shows different pa tterns for acute and chronic states. In acute schizophrenia there is a dysrhythmic activity with an increase in beta-activity. This is count eracted by neuroleptics, inducing slowing of frequency and an increase of synchronization. In chronic schizophrenics, there is an increased synchronization with low variability of amplitude. In contrast to the treatment in acute schizophrenics, in chronic schizophrenia the therap y response under neuroleptics is indicated by an increase in beta-acti vity and a decrease in synchronization.