Functional interhemispheric differences in relation to various psychopathological components of the depressive syndromes. A pilot international study.

Previous investigations from our laboratory have suggested a possible interhemispheric difference in brain functioning in relation to the severity of a depressive psychopathological process. The present study has been carried out to extend the previous findings to comprise a more detailed symptom analysis of the depressive syndrome, several EEG characteristics, and a new method of EEG analysis. 22 depressed patients, most of them previously untreated, participated in the study. The patients were rated by means of a highly reliable rating scale for depression, and an EEG record was obtained from each of them. Analysis of possible relationships among clinical symptoms and EEG characteristics from different parts of the brain showed a complex pattern, quite different for each symptom. First when a systemic structural analysis of the EEG was performed by means of a special computer program, differential EEG syndromes could be identified. Patients with a high level of anxiety-depression showed a more pronounced functional involvement of the left precentral region than less severely ill patients.