Sedation threshold; a neurophysiological tool for psychosomatic research.

Abstract

Summary The sedation threshold is an objective pharmacological determination which represents the amount of intravenous Sodium Amytal required to elicit certain EEG and speech changes. The purpose of this paper was to present the evidence which bears on the validity of this method as a clinical neurophysiological approach to investigation of psychopathological problems. Data were drawn from tests on over 500 psychiatric patients and 45 nonpatient controls. The following general results were obtained: (a) The sedation threshold was positively correlated with degree of manifest anxiety in nonpsychotic subjects. The greater the manifest anxiety in psychoneurotics or control subjects, the higher the threshold. (b) Obsessional personality characteristics tended to be associated with a high threshold, hysterical characteristics with a low threshold. (c) The sedation threshold was negatively correlated with degree of gross impairment of ego functioning in psychotics. The greater the ego impairment, the lower the threshold. (d) The threshold differentiated between neurotic and psychotic depressions with a high degree of accuracy. Thresholds were low in psychotic depressions and high in neurotic depressions. It was concluded that the sedation threshold was meaningfully related to several important psychopathological phenomena, and that the results supported its validity as an investigative approach. The findings were discussed from the following standpoints: clinical and research applications; some neurophysiological aspects of anxiety, depression, and ego functioning; and relation to personality theory, with special emphasis upon Eysenck's theory.