ON THE EFFICACY OF ALCOHOL PLACEBOS IN INDUCING FEELINGS OF INTOXICATION

Placebo efficacy was monitored during three separate experiments conce rned with the effects of ethanol (0.8 ml/kg body weight) on some aspec t of performance: at regular intervals during experimental sessions, b lood alcohol concentration was estimated using a breathalyser and subj ects completed an intoxication rating. The simple placebo beverages an d manipulations employed were similar to those typically described in the literature, and each experiment involved a repeated measures desig n. Across the three experiments, maximum mean (median) ratings during placebo sessions, expressed as a percentage of those during alcohol se ssions of equivalent period, ranged between 10% (0%) and 69% (72%), an d the number of subjects in each experiment for whom a placebo effect was considered to have been negligible ranged between 8% and 73%. For each treatment, intoxication ratings were higher during treatment peri ods which occurred first than during those which occurred second. Howe ver, this transfer effect was twice as large for placebo treatments as for alcohol treatments and, whereas in respect of the latter the effe ct was statistically non-significant, it was highly significant in res pect of the former. The occurrence of such asymmetrical transfer of pl acebo efficacy suggests that repeated measures designs should be used with caution in drug studies in which a convincing placebo treatment i s necessary and difficult to devise.