The sample for the present study came from the Finnish population-based FinnTwin12 cohort, which is a longitudinal twin study designed to examine genetic and environmental influences on precursors to health outcomes, especially alcohol use (Kaprio et al., 2002). FinnTwin12 includes twins identified through Finland’s Population Registry Center from five consecutive birth cohorts (1983–1987) collected from 1994 to 1998 comprised of 11–12 year old twins. An initial family questionnaire was sent to all eligible twin families late in the year before the twins turned 12 years old and received an 87% response rate. Additional baseline questionnaires were mailed to those families who returned the family questionnaire. Zygosity was assessed at this point by a well-validated questionnaire completed by both twins (Kaprio et al., 2002). Further follow-up questionnaires were sent at ages 14 and 17.5 years old, with the addition of age-specific items on health behaviors such as alcohol use and abuse. Here we focus on data from the age 14 assessment (88% response rate), which included questions about alcohol use, parental knowledge, peer deviance, and stressful life events. The sample used
