PSYCHOLOGIC EFFECTS OF AMPHETAMINES AND BARBITURATES

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Abstract
To determine whether psychologic functions are selectively affected by classic CNS stimulants and depressants, objective and subjective measures oi various intellectual functions were obtained before and after medication with therapeutic doses of amphetamines and barbiturates, administered singly or in combination. Two hundred forty normal adult volunteers were each assigned to one of six treatments (including four active medications in sustained-release form, and two placebos) according to a randomized blocks design. Three active medications (10 nag dextro-amphetamine sulfate; 10 mg. dextro-amphetamine sulfate plus 65 mg. amobarbital; and 65 mg phenobarbital) and one placebo were administered in capsules identical in appearance, to help to maintain double-blind conditions. Corresponding to the fourth active medication (10 mg methamphetamine hydrochloride plus 65 mg phenobarbital) was a tablet placebo identical to it in appearance. Since test results for the capsule and tablet placebos failed to differ, results for both placebos were combined, and results for all four active medications (including capsule and tablet doses) were compared within the framework of a single analysis. The soporific action and the easier flow of associations observed with heavier barbiturate doses were noted with phenobarbital, but the present phenobarbital dose was too mild to produce statistically significant effects. The remaining three active doses each contained an amphetamine, and findings for these doses primarily reflect the actions of the amphetamines. Present as well as earlier findings indicate that the amphetamines exert rather uniformly positive effects on a wide range of measures. The amphetamines thus differ from caffeine, the effects of which are less generally beneficial. The simultaneous improvement of a variety of performances by the amphetamines suggests that these drugs enhance general intellectual capacity. The amphetamines appear to produce their intellectual effects, at least in part, by enabling Ss to pay closer attention to intellectual tasks confronting them. The fundamental role here assigned to the alerting action of the amphetamines further suggests that both capacity effects and antihypnotic effects are effected through, and regulated by, a common center, such as the reticular formation.