Dose-response analysis of the behavioral effects of diazepam: II. Psychomotor performance,cognition and mood

The psychomotor, cognitive, and mood effects of orally administered diazepam and placebo were measured over 3.5 h. A total of 120 volunteers were assigned to 12 groups of 10 each, representing the combination of four treatments (placebo, 0.1, 0.2, and 0.3 mg/kg diazepam) and three testing sessions (7 AM, 1 PM, and 7 PM). A variety of cognitive tasks, tapping and postural stability tests, and a mood evaluation scale were used. Psychomotor and cognitive functions showed consistent dose-response effects, while for subjective evaluations, the only effect of dose level was in the duration of sedation. The pattern of impairment of cognitive functions suggests that the drug affects speed rather than accuracy, and it primarily blocks acquisition of new information or skills. Use of repeated testing may therefore be necessary to detect subtle drug effects. Subjects reported no tranquilization, which suggests that the anxiolytic action of the drug cannot be studied in healthy volunteers. There was no circadian influence on the actions of the drug.