Individual differences in the biphasic effects of ethanol

Ethanol exerts both stimulant-like and sedative-like subjective and behavio ral effects in humans depending on the dose, the time after ingestion and, we will argue, also on the individual taking the drug. This study assessed stimulant-like and sedative-like subjective and behavioral effects of ethan ol during the ascending and descending limbs of the blood alcohol curve acr oss a range of doses in nonproblem social drinkers. Forty-nine healthy men and women, 21 to 35 years old, consumed a beverage containing placebo or et hanol (0.2, 0.4, or 0.8 g/kg) on four separate laboratory sessions, in rand omized order and under double-blind conditions. Subjective and behavioral r esponses were assessed before and at regular intervals for 3 hr after inges tion of the beverage. The lowest dose of ethanol (0.2 g/kg) only produced n egligible subjective effects compared to placebo. The moderate dose (0.4 g/ kg) increased sedative-like effects 90 min after ethanol ingestion but did not increase ratings of stimulant effects at any time. The highest dose (0. 8 g/kg) increased ratings of both stimulant- and sedative-like effects duri ng the ascending limb and produced only sedative-like effects during the de scending limb. Closer examination of the data revealed that individual diff erences in response to the highest dose of ethanol accounted for this unexp ected pattern of results: about half of the subjects reported stimulant-lik e effects on the ascending limb and sedative-like effects on the descending limb after 0.8 g/kg ethanol, whereas the other half did not report stimula nt-like effects at any time after administration of ethanol. These results challenge the simple assumption that ethanol has biphasic subjective effect s across both dose and time, and extend previous findings demonstrating ind ividual differences in response to ethanol.