Each day in the United States, approximately 4,000 adolescents initiate cigarette smoking1, and data from annual surveys suggest that the decade-long decline in teenage smoking has recently slowed2. Researchers consistently report that lifetime exposure to parent smoking predicts offspring tobacco use3-5. Two issues arise in the evaluation of this literature. The first involves the manner in which smoking behavior is transmitted from parent to offspring. In non-adoptive families, genetic and environmental effects are confounded6. Thus, the observation that the birth children of smoking parents have elevated rates of tobacco use does not tell us whether the basis for this association is environmental (e.g., smoking parents model or otherwise encourage tobacco use) or genetic (e.g., smoking parents transmit genes that increase their offspring's liability for tobacco use). In their review of the genetic epidemiology of smoking, Sullivan and Kendler7 concluded that both genetic and shared familial environmental factors contributed to smoking behavior, suggesting that these factors could be acting jointly to increase the risk for tobacco use in the offspring of smokers.
