had lower insular and frontal GMVs (Figure 2C, D; Table S2 in Supplement 1). Further, GMVs did not differ between low and high alcohol-using members of discordant pairs. As shared genetic and familial factors are matched within pairs, this pattern of results suggests that smaller frontal gyri and insula GMVs may reflect preexisting vulnerability factors associated with alcohol use, as opposed to a consequence of alcohol use.
