Alcohol does not influence trust in others or oxytocin, but increases positive affect and risk-taking: a randomized, controlled, within-subject trial.

Background: Alcohol consumption to facilitate social interaction is an important drinking motive. Here, we tested whether alcohol influences trust in others via modulation of oxytocin and/or androgens. We also aimed at confirming previously shown alcohol effects on positive affect and risk-taking, because of their role in facilitating social interaction.

Methods: This randomized, controlled, within-subject, parallel group, alcohol-challenge experiment investigated the effects of alcohol (versus water, both mixed with orange juice) on perceived trustworthiness via salivary oxytocin (primary and secondary endpoint) as well as testosterone, dihydrotestosterone, positive affect, and risk-taking (additional endpoints). We compared 56 male participants in the alcohol condition (1.07 ± 0.18 per mille blood alcohol concentration) with 20 in the control condition.

Results: The group (alcohol versus control condition) × time (before [versus during] versus after drinking) interactions were not significantly associated with perceived trustworthiness (η < 0.001) or oxytocin (η = 0.003). Bayes factors provided also substantial evidence for the absence of these effects (BF = 3.65; BF = 7.53). The group × time interactions were related to dihydrotestosterone (η = 0.018 with an increase in the control condition) as well as positive affect and risk-taking (η = 0.027 and 0.007 with increases in the alcohol condition), but not significantly to testosterone.

Discussion: The results do not verify alcohol effects on perceived trustworthiness or oxytocin in male individuals. However, they indicate that alcohol (versus control) might inhibit an increase in dihydrotestosterone and confirm that alcohol amplifies positive affect and risk-taking. This provides novel mechanistic insight into social facilitation as an alcohol-drinking motive.