To our knowledge, only one other adoption study has examined the effect of parent smoking in adoptees38. These authors reported that both adoptive and birth parent smoking were unrelated to ever smoking in adopted adults. However, this Danish, registry-based sample included adoptions from 1924-1947, a period during which smoking was highly prevalent. Although restriction in range likely attenuated the association between parents and offspring in that study, the factors that influenced risk for smoking behavior during that period may be different from those that are operating today39.
