Familial and socioregional environmental effects on abstinence from alcohol at age sixteen.

OBJECTIVE This study identifies, in genetically informative data, familial and socioregional environmental influences on abstinence from alcohol at age 16. METHOD Data are from FinnTwin 16, a population-based study of five consecutive birth cohorts of Finnish twins (N = 5,747 twin individuals), yielding 2,711 pairs of known zygosity. Measures of alcohol use, embedded into a health-habits questionnaire, were taken from earlier epidemiological research with nontwin Finnish adolescents. The questionnaire was administered sequentially to all twins as they reached age 16. Separate questionnaires, including measures of alcohol use and screening questions for alcohol problems, were received from 5,243 of the twins' parents. RESULTS Abstinence from alcohol to age 16 exhibits very significant familial aggregation, largely due to nongenetic influences. Abstinence rates are influenced by socioregional variation, sibling interaction effects and parental drinking patterns. Sibling and parental influences are greater in some regional environments than in others: the relative likelihood that a twin abstains, given that the co-twin does, or that both parents do, is shown to be modulated by socioregional variation. CONCLUSION Environmental contexts affect the likelihood of maintaining abstinence from alcohol to midadolescence, and socioregional variation modulates influences of siblings and parents. The results illustrate how genetically informative data can inform prevention research by identifying target variables for intervention efforts.