Using Placebo Beverages in Group Alcohol Studies

Background: Placebo beverage conditions remain a key element in the methodological toolkit for alcohol researchers interested in evaluating pharmacological and nonpharmacological factors influencing the effects of alcohol consumption. While interest in experimentally examining alcohol in social context is on the rise, there has been little research examining the effectiveness of placebo manipulations in group settings, when just 1 suspicious participant could potentially jeopardize the effect of the placebo on group members. Moreover, research has rarely considered the association between individual difference factors (e.g., gender) and placebo manipulation effectiveness. The present study, using an uncommonly large sample of placebo-consuming participants, was well suited to investigate fundamental questions regarding placebo efficacy that have not been assessed previously. Specifically, we aimed to examine placebo efficacy and general processes of placebo functioning in a group context. We also assessed potential associations between a variety of individual difference factors and placebo response. Methods: A total of 240 participants (50% male) consumed placebo beverages during a triadic drinking period (across 80 three-person groups). Participants reported their subjective intoxication, stimulation, and sedation 8 minutes following drink consumption and estimated the alcohol content of their drink at the end of the study. Results: Participants consuming placebo beverages in groups were nearly universal in reporting that they had consumed alcohol (>99%) and had experienced an increase in feelings of intoxication [t(239) = 22.03, p < 0.001] and stimulation [t(239) = 5.53, p < 0.001], levels that were similar to those observed in prior studies conducted with participants drinking placebos in isolation. Further, participants' placebo responses were independent of their 2 group members and were largely unaffected by a variety of individual difference factors. Conclusions: Placebo response generally operated independently of group-member influences, suggesting that researchers can successfully conduct placebo beverage studies utilizing group drinking designs.