Genetic and environmental influences on adolescents' smoking involvement: a multi-informant twin study

Familial and Special Twin Influences on Cigarette Use Initiation

BACKGROUND

Shared experiences within families play an important role in the initiation of cigarette use among adolescents. Behavioral genetic studies using various samples have implicated that the shared environment that twins experience is an important source of influence on whether adolescents initiate cigarette use. Whether the special twin environment, in addition to the shared environment, contributes significantly to making twin siblings more similar in cigarette initiation, and whether the influence of the special twin environment persists into adulthood, is less clear.

METHODS

Data for this study came from the National Longitudinal Survey of Adolescent Health. Twin, full-, and half-sibling pairs between the ages of 12 and 33 were separated into three age groups, with about 3,000 individuals in each age group. The proportion of variance in cigarette use initiation explained by genetic, shared, special twin, and unique environmental factors were examined.

RESULTS

The results of separate age-moderated univariate variance decomposition models indicate that the special twin environment does not significantly contribute to the variance in cigarette use initiation in adolescence or young adulthood.

CONCLUSION

Factors shared by individuals in a family, but that are not specific to being a twin, are important in determining whether adolescents will initiate the use of cigarettes.

Genetic and environmental contributions to initiation of cigarette smoking in young African-American and European-American women

BACKGROUND

Distinctions in the relative contributions of genetic and environmental factors to initiation of cigarette smoking may explain, in part, the differences between African Americans and European Americans in the prevalence of smoking. The current investigation is the first to compare heritable and environmental influences on smoking initiation between African-American and European-American women.

METHODS

Data were drawn from Missouri Adolescent Female Twin Study participants and female Missouri Family Study participants (n=4498; 21% African-American, the remainder European-American). Mean ages at first and last assessments were 17.0 (SD=3.5) and 24.0 (SD=3.2), respectively. Twin-sibling modeling was conducted to estimate the proportion of variance in smoking initiation (i.e., ever trying a cigarette) attributable to additive genetic, shared environmental, special twin environmental, and unique environmental factors.

RESULTS

Additive genetic influences accounted for approximately half of the variance in smoking initiation in both African-American and European-American women. In the African-American subsample, the remaining variance was attributable primarily to unique environmental factors (46%; 95% CI: 28-71%). In the European-American subsample, only 12% (95% CI: 8-16%) of the variance was attributable to unique environmental factors, with the remainder accounted for by shared environmental (13%; 95% CI: 0-41%) and special twin environmental (24%; 95% CI: 0-52%) factors.

CONCLUSIONS

The estimated heritability of smoking initiation is substantial and nearly identical for African-American and European-American women, but the type of environmental factors that contribute to risk differ by race/ethnicity. Whereas the primary environmental influences on European-American women's smoking initiation are at the family level, those that impact African-American women's smoking initiation are primarily individual-specific.