Prototype Specificity Matters When Predicting Later Alcohol-Related Content Posting and Alcohol Use Among Adolescent and Young Adults.

: Drinking prototypes (i.e., images of the type of individual who engages in specific alcohol use behaviors) are associated with alcohol use, with self-identified similarity to the prototype possibly driving this connection more than one's favorability of the prototype. Alcohol-related content (ARC; posts featuring alcohol or drinking) posting prototype favorability is also associated with ARC posting and drinking. However, the effects of ARC posting prototype similarity on posting or drinking behavior are unexamined. Prior research suggests specificity of antecedents (e.g., attitudes, prototypes) matters in predicting subsequent behavior. The current study examined which types of prototype similarity (e.g., drinking, ARC posting) are most strongly associated with later ARC posting and drinking behavior, respectively. : Adolescents and young adults who reported alcohol use ( = 274) were recruited to complete two online surveys at baseline and 1-month later. : Controlling for abstaining, heavy episodic drinking (HED), and ARC posting prototype similarity, only greater baseline ARC posting prototype similarity was associated with posting ARC 1-month later. Zero-inflated negative binomial regressions revealed greater abstaining prototype similarity was associated with lower drinking frequency 1-month later. Higher HED prototype similarity was associated with likely drinking on at least one day in the past month (i.e., drinking frequency). Higher ARC posting prototype similarity was associated with likely reporting no negative alcohol consequences. : Findings suggest that interventions targeting reductions in ARC posting should aim to change ARC posting prototype similarity whereas drinking prototype similarity should be highlighted in alcohol interventions.