The “Sleep” Threshold. a Simple Form of the Sedation Threshold for Clinical Use

This study was conducted for two purposes: (a) To determine the relationship between the sedation threshold, derived from EEG changes, and the amount of amobarbital required to induce “sleep”, which was defined as unresponsiveness to verbal stimulation, (b) To determine the relationships between the “sleep” threshold and psychiatric diagnosis. 2. In 91 patients, the correlation between the “sleep” and sedation thresholds was +0.66. 3. In the 91 patients with “sleep” thresholds and 110 additional patients, whose “sleep” thresholds were not reached, but were more than 7mgm./Kg., the relationships between the “sleep” threshold and psychiatric diagnosis were generally similar to those obtained with the sedation threshold. The finding that both thresholds provided an equally high degree of differentiation between neurotic and psychotic depression was of particular interest. 4. The “sleep” threshold appears to provide a simple clinical test for psychiatric diagnosis, as no apparatus is required. The discovery of a critical threshold point in relation to diagnosis further simplifies the procedure, insofar as it would not be necessary to reach the “sleep” point in all patients, but only to give more amobarbital than the critical point. However, the “sleep” threshold may possibly be influenced by variations in environment and observer, and it was suggested that investigators, wishing to use the “sleep” threshold test, should determine standards for their own test setting.