recall biases in self-reports of past drinking behavior (Engels et al. 1997.; Labouvie et al. 1997). Accordingly, examining these effects with prospective alcohol use data would circumvent the recall biases. Third, previous studies have also indicated that other aspects of familial transmission, including sibling relationships (Penninkilampi-Kerola et al., 2005) may modulate genetic influences on alcohol use behaviors, particularly in adolescence. Integrating these non-genetic family dynamics into models examining genetic risk for problematic alcohol use may elucidate important differences among those with same sex and opposite sex co-twins.
