EEG techniques in the measurement of the severity of depressive syndromes.

Previous results from our laboratory support the hypothesis that measurements of EEG mean integrated amplitude (MIA) are correlated with the depth of depression as assessed by a rating scale, and also with the degree of memory impairment during depression. Moreover, it could be shown that there occurs, during severe depression, a more pronounced involvement of the dominant (DH) than of the non-dominant (NDH) brain hemisphere. A similar interhemispheric difference has also been found in a previous study of visual averaged evoked responses (V.AER). A new series comprising 51 untreated depressed patients has been investigated for both MIA and V.AER to extend the previous findings. In agreement with previous results a significant negative correlation between the within patient variance (WPV) of the MIA and depression scores was found. Moreover, a statistically significant negative relationship between the amplitude of the first two V.AER and depression scores was obtained. Since DH is most important for verbal functions, it is assumed that the degree of involvement of the DH is more pronounced in retarded depressed patients with pronounced speech disturbances.