Psychological Effects and Alcohol-Antagonizing Properties of Caffeine

Abstract

Some of the inconsistent findings on ,the effects of caffeine on human performance and subjective state, and on its supposed antagonism of alcohol-induced impairment, are discussed. The recent findings of Forney and Hughes (Quart. J. Stud. Ale. 26: 206—212, 1965) of a trend toward caffeine-induced deficit in human performance are examined in relation to Nash's findings (Alcohol and Caffeine; a Study of their Psychological Effects. Springfield; Thomas; 1962) of an over-all enhancement effect of caffeine on various measures of intellectual capacity. Comparison of the methodology and findings in the two studies suggests that the results are not contradictory; and that the effects of caffeine on performance are largely favorable but selective. Other reviewed findings appear to be in accord with this conclusion. The findings concerning the questioned caffeine—alcohol antagonism appear to be even more controversial. Contributing to the difficulty of arriving at a simple conclusion are such factors as variations in tasks studied, variations in dosage levels of the two drugs, and limited numbers of subjects. A brief review of some of the findings on the combined effects of alcohol and caffeine suggests that only the following conclusions appear to be warranted: Caffeine—alcohol antagonism possibly varies with the psychological function and with the dosage level of the two drugs; antagonism is possibly absent or negligible under certain conditions; enhancement by caffeine of an alcohol-induced impairment in performance in human subjects has yet to be demonstrated; further research is needed to establish the limits of the caffeine—alcohol antagonism. Some practical implications of these conclusions for automobile drivers who drink alcoholic beverages are discussed.