Perceived changes in drinking are a mechanism of spillover effects from a brief alcohol intervention conducted in a...

In a prior clinical trial, heavy drinkers in a network of first-year college students who had reciprocal network ties with recipients of a brief motivational intervention (BMI) showed a reduction in alcohol use. The objective of the present study was to identify the mechanisms through which this spillover effect occurred.

Heavy-drinking participants (N = 148) who had a reciprocal network tie (i.e., were close friends) with a BMI intervention recipient or a natural history control were identified (index participants; N = 83), and three models investigated putative mechanisms of change in close friend drinking from baseline to 5-month follow-up: (a) close friend perception of BMI/natural history control index participant past-month maximum number of drinks, (b) community perception of index participant maximum drinks, and (c) change in community perception of index participant maximum drinks from baseline to follow-up. The community perception was the average of available perceptions of the index participant maximum drinks. Models included index participant self-reported change in drinking as a proximal mediator and adjusted for close friend sex.

Close friend perception that BMI index participants reduced their drinking was related to their own reductions in drinking. Models with aggregate perception of index participant behavior as mediators were not significant, though significant paths support hypothesized directional effects.

Perception of peer drinking, an established predictor of alcohol use and a mechanism of behavior change in brief interventions, is a possible conduit through which a brief alcohol intervention transmits its spillover effects to close peers. (PsycInfo Database Record (c) 2026 APA, all rights reserved).