Genes and inheritance each play a key role in determining a person’s vulnerability to regular tobacco use, a generation-spanning study of twins has confirmed.

For women, the genetic element of their vulnerability to smoking has increased as society’s once-strong taboos against tobacco use by women have diminished, the study revealed.

Among men, the patterns of tobacco use suggest genetic and environmental factors account, respectively, for 61 percent and 20 percent of the differences in individuals in their risk for becoming regular users of tobacco. In women born before 1925, rates of tobacco use were low, based largely on environmental factors. For women born since 1940, however, heritability of tobacco use is essentially the same as in men — 63 percent.

The study was conducted by Dr. Kenneth S. Kendler of the Medical College of Virginia and researchers at the Karolinska Institute in Stockholm, Sweden. The results were published in the September issue of the Archives of General Psychiatry. Copies of the article are available at the Web site, www.archpsyc.ama-assn.org.