In the present study, we expanded the previous findings from Kendler et al. (2010) using longitudinal Finnish twin data from the population-based FinnTwin12 cohort study. First, we sought to replicate previous findings in examining the impact of alcohol-specific and non-specific (general externalizing) genetic factors on alcohol use behaviors from early adolescence (age 12) through early adulthood (age 22) using prospective reports in both male and female twins from same-sex and opposite-sex twin pairs. However, our main goal was to extend this work by examining whether the influence of genetic risk for alcohol use behaviors was moderated by sex of the twin, given sex differences documented across alcohol use behaviors. Finally, our third goal was to examine whether the sex of the co-twin impacted genetic risk for alcohol use behaviors across development.
