Alcohol effects on brain function were analyzed using a hierarchical multiple regression (HMR) analysis of the amplitude and latency values of ERPs and self-reported alcohol use measures. An HMR approach was used to model the influence of a co-twin's measured effects on the ERP variables being studied in each twin, taking into account other covariates of the twin and variables common to both co-twins of each pair, including their zygosity. The HMR analysis permits testing for main effects and interactions among genetic factors, alcohol use, and ERP change: Heitmann and colleagues (1997), Kaprio and colleagues (1987), and Rose and colleagues (1988) illustrate HMR analyses of other measures.
