Familial resemblances in alcohol use: genetic or cultural transmission?

OBJECTIVE Resemblances between parents and children for alcohol use can be due both to cultural transmission and genetic inheritance. We examined the genetic and environmental determinants of the familial resemblances in alcohol use. METHOD With a parent-twin design a distinction was made between the contribution of genetic effects, the environmental influences shared by siblings and the effects of cultural transmission from parents to offspring. By questionnaire data on whether subjects had ever used alcohol were obtained from 403 Dutch families with a twin aged 15-16 years old and from 805 families with a twin aged 17 years and older. RESULTS For 15-16 year olds, the resemblance between parents and offspring could be explained either by genetic inheritance or cultural transmission. Shared environment explained between 58% and 88% of the individual differences in adolescent alcohol use. For twins aged 17 years and older, 43% of the individual differences in alcohol use could be attributed to genetic factors and 37% to shared environment. There was no evidence for cultural transmission in this age group. CONCLUSIONS For adolescents aged 17 years and older parental alcohol use did not create an environment that stimulated alcohol use in children. The resemblance for alcohol use between parents and their children aged 17 years and older could be explained by their genetic relatedness. For 15-16 year old adolescents, shared environmental influences were more important than for older adolescents. Only 10% of this shared environmental variance might be influenced by parental alcohol use due to cultural transmission.