concordant pairs: n = 117; aAUDIT-C mean = 0.84, SD = 0.77; high alcohol concordant pairs: n = 54; aAUDIT-C mean = 7.08, SD = 1.4). There were 72 discordant sibling pairs (“low discordant”; aAUDIT-C mean = 1.25, SD = 0.73; “high discordant”; aAUDIT-C mean = 6.47, SD = 1.67). Participants could be included in >1 pair (n = 368 individuals) when considering relationships with multiple siblings. Discordancy analyses were conducted using linear mixed models, using the psych (52) and lme4 (53) packages in R (54) to account for the multiple-sibling structure within families. Covariates were identical to those used in neuroimaging analyses. Additional information on models tested and their interpretation are available in Supplement 1.
