Tobacco, alcohol and drug use in eight- to sixteen-year-old twins: The Virginia Twin Study of Adolescent Behavioral Development

Objective: This study reports prevalences of lifetime and current alcohol, tobacco and drug use in adolescents; examines associations between substanc e use and a number of putative risk factors; and estimates the contribution of genetic, shared and unique environmental influences on substance use. M ethod: Substance use data were collected using the Child and Adolescent Psy chiatric Assessment on a population sample of 1,412 male and female monozyg otic and dizygotic twin pairs, aged 8 through 16, from the Virginia Twin St udy of Adolescent Behavioral Development. Results: Heritabilities were esti mated to be 84% and 82% for liability to lifetime and current tobacco use, respectively. For alcohol use the role of genes and environment varied acco rding to the context of reporting. Liability to lifetime alcohol use was es timated to be under environmental control, with 71% of the variation shared by members of a twin pair and 29% unique to individual twins. Lifetime alc ohol use without the permission of a parent or guardian and current use of alcohol were predominantly explained by genetic factors (h(2) = 72% and 74% ). The role of genetic factors increased and that of unique environmental f actors decreased with increasing severity of alcohol use. Lifetime use of a ny drug showed a heritability of 45%, with the shared environment accountin g for 47% of the variation. Shared environmental factors explained most of the variation in marijuana use. Conclusions: Genetic factors explained a si gnificant proportion of the variation in the use of tobacco. alcohol and ot her drugs. Shared environmental factors contributed significantly to lifeti me alcohol use and other drug use.