Effect of setting on the reinforcing and subjective effects of ethanol in social drinkers.

The reinforcing and subjective effects of two doses of ethanol [0.5 g/kg (LOW) and 0.8 g/kg (HIGH)] were evaluated under two conditions, a social condition (SOC), in which subjects were tested with two or three other subjects, and a socially isolated condition (ISO), in which subjects were tested alone. Forty-one social drinkers participated in a double-blind, seven-session choice procedure. Subjects were randomly assigned to one of four experimental groups: SOC-LOW, SOC-HIGH, ISO-LOW, or ISO-HIGH. On the first four sessions, subjects sampled ethanol (0.5 or 0.8 g/kg) on two occasions and placebo on the other two occasions. On the three remaining sessions, subjects selected and consumed whichever of the two previously sampled substances they preferred. The number of sessions on which they chose ethanol was the primary measure of the reinforcing effects of ethanol. Standardized self-report questionnaires and a psychomotor test were used to measure subjective and objective drug effects. Subjects in the SOC condition chose ethanol over placebo on significantly more sessions than subjects in the ISO condition. Ethanol produced positive subjective effects (e.g., increased ratings of drug liking and euphoria) for subjects in the SOC condition, but for subjects in the ISO condition, it produced apparently negative effects (e.g., increased ratings of dysphoria). These results extend previous reports that the behavioral effects of ethanol depend upon the social condition in which it is consumed.