The Genetic and Environmental Influences Contributing to the association between Electronic and Conventional Cigarette Initiation.

Introduction:
This text summarizes a twin study examining the genetic and environmental influences on the initiation of electronic cigarettes (EC) and conventional cigarettes (CC) among adolescents and young adults. The study aims to determine the degree of correlation between EC and CC initiation, the extent to which the correlation is due to shared genetic and environmental factors, and the degree to which genetic and environmental influences are specific to EC initiation.

Key Points:

* The study uses data from the adolescent and Young adult Twin Study (aYaTS), which includes 858 individuals (421 complete twin pairs).
* Lifetime EC initiation was measured using a five-item ordinal variable, while lifetime CC initiation was measured using a binary variable.
* The study uses the classical twin study design, which compares correlations between monozygotic (MZ) and dizygotic (DZ) twin pairs to estimate additive genetic influences, shared environmental influences, and unique environmental influences.
* The results show a moderate to large cross-twin correlation for EC initiation and CC initiation.
* No significant quantitative or qualitative sex differences were detected, but significant differences in liability thresholds by sex were detected.
* Common environmental influences accounted for a nonsignificant proportion of the variance in the liability of EC and CC initiation.
* The contribution of additive genetic influences on the initiation of both delivery systems was nonsignificant.
* There was a strong phenotypic correlation between EC and CC initiation, which was due to nonsignificant common environmental covariance, nonsignificant additive genetic covariance, and significant unique environmental covariance.
* The unique environmental correlation was significant between both delivery systems.

Main Message:
The study suggests that both genetic and environmental factors play a role in EC and CC initiation. While there is a strong phenotypic correlation between EC and CC initiation, the genetic and environmental influences are largely unique to each behavior. The study highlights the importance of examining the unique environmental factors that contribute to both delivery systems, such as peer smoking, opinions toward nicotine products, and exposure to tobacco marketing. The results provide preliminary evidence for genetic and environmental influences involved in EC initiation and unique environmental as well as familial overlap between EC and CC initiation. Further research is needed to confirm these findings and to better understand the complex relationship between EC and CC initiation.

Prom-Wormley EC, Clifford JS, Cooke ME, et al. The Genetic and Environmental Influences Contributing to the association between Electronic and Conventional Cigarette Initiation. Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco. 2021;23(5):856-860. doi:10.1093/ntr/ntaa201