Our analyses address a long-standing question: Does adolescent alcohol abuse have demonstrable effects on neurophysiological function in early adulthood? Our results, most consistently found in an association of a lifetime report of high-density drinking with novel P3, offer some positive answers. Maximum number of drinks consumed in a 24-hour period, MAX-24D, significantly correlated (negatively), across all 358 twins, with the amplitude of novel P3 from all 3 measured electrode sites. Importantly, and convincingly, the between-family association of MAX-24D with novel P3 amplitude was fully confirmed in within-family analysis of twin pairs, an analysis that correlated intrapair differences in MAX-24D with intrapair differences in novel P3 amplitudes for all 177 twin pairs. The magnitude of these correlations was modest, but we emphasize that the pairwise correlations of intrapair differences (ranging from −0.20 to −0.28 across the 3 P3 sites) were fully consistent with the parallel correlations based on the twins as individuals (−0.18 to −0.21). Correlations of intrapair differences in alcohol use with intrapair differences in P3 offer some within-family control for many unmeasured between-family confounds, including family history and parental
