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Introduction: Previous studies in adolescents were not adequately powered to accurately disentangle genetic and environmental influences on smoking initiation (SI) across adolescence., Methods: Mega-analysis of pooled genetically informative data on SI was performed, with structural equation modeling, to test equality of prevalence and correlations across cultural backgrounds, and to estimate the significance and effect size of genetic and environmental effects according to the classical twin study, in adolescent male and female twins from same-sex and opposite-sex twin pairs (N = 19 313 pairs) between ages 10 and 19, with 76 358 longitudinal assessments between 1983 and 2007, from 11 population-based twin samples from the United States, Europe, and Australia., Results: Although prevalences differed between samples, twin correlations did not, suggesting similar etiology of SI across developed countries. The estimate of additive genetic contributions to liability of SI increased from approximately 15% to 45% from ages 13 to 19. Correspondingly, shared environmental factors accounted for a substantial proportion of variance in liability to SI at age 13 (70%) and gradually less by age 19 (40%)., Conclusions: Both additive genetic and shared environmental factors significantly contribute to variance in SI throughout adolescence. The present study, the largest genetic epidemiological study on SI to date, found consistent results across 11 studies for the etiology of SI. Environmental factors, especially those shared by siblings in a family, primarily influence SI variance in early adolescence, while an increasing role of genetic factors is seen at later ages, which has important implications for prevention strategies., Implications: This is the first study to find evidence of genetic factors in liability to SI at ages as young as 12. It also shows the strongest evidence to date for decay of effects of the shared environment from early adolescence to young adulthood. We found remarkable consistency of twin correlations across studies reflecting similar etiology of liability to initiate smoking across different cultures and time periods. Thus familial factors strongly contribute to individual differences in who starts to smoke with a gradual increase in the impact of genetic factors and a corresponding decrease in that of the shared environment., (© The Author 2017. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Little is known regarding the underlying relationship between smoking initiation and current quantity smoked during adolescence into young adulthood. It is possible that the influences of genetic and environmental factors on this relationship vary across sex and age. To investigate this further, the current study applied a common causal contingency model to data from a Virginia-based twin study to determine: (1) if the same genetic and environmental factors are contributing to smoking initiation and current quantity smoked; (2) whether the magnitude of genetic and environmental factor contributions are the same across adolescence and young adulthood; and (3) if qualitative and quantitative differences in the sources of variance between males and females exist. Study results found no qualitative or quantitative sex differences in the relationship between smoking initiation and current quantity smoked, though relative contributions of genetic and environmental factors changed across adolescence and young adulthood. More specifically, smoking initiation and current quantity smoked remain separate constructs until young adulthood, when liabilities are correlated. Smoking initiation is explained by genetic, shared, and unique environmental factors in early adolescence and by genetic and unique environmental factors in young adulthood; while current quantity smoked is explained by shared environmental and unique environmental factors until young adulthood, when genetic and unique environmental factors play a larger role.

Objective: To examine the effects of maternal substance use on neonatal outcomes in 212 pregnant cocaine/opiate dependent women who delivered while in active drug treatment., Study Design: Using urine toxicology data at delivery, subjects were classified drug positive (+TOX) (n = 53) or negative (-TOX) (n = 159)., Results: Toxicology status was not associated with maternal or neonatal demographic or drug use variables. +TOX patients were enrolled in the treatment program for a shorter period of time than -TOX (68.3 vs. 91.3 days, p = 0.005). Infant birth weight ratio (IBR) was lower in +TOX women (0.84 vs. 0.90, p = 0.003). +TOX women were twice as likely to have small-for-gestational-age (IBR < 0.85) neonates than were -TOX. Length of stay (LOS) in the neonatal intensive care unit (NICU) was not associated with maternal toxicology but was associated with quantity of tobacco per day (p = 0.0001). NICU neonates with heavily smoking mothers (11+ cigarettes/day) averaged LOS = 9.5 days as compared to light (1-10 cigarettes per day) smokers (LOS = 7.9 days) and nonsmokers (LOS = 5.5 days)., Conclusion: Maternal drug abstinence is associated with higher IBR. Maternal smoking is related to NICU LOS, even among polydrug-dependent women. These data are clinically and economically important and support the need for smoking cessation interventions in high-risk populations, such as drug-dependent pregnant women.

Prochaska and DiClemente's Transtheoretical Model predicts dropout from substance-abuse treatment. However, it is not known whether readiness to quit smoking is associated with attrition from drug treatment programs with smoking restrictions. This study examined the relationship between smoking characteristics, smoking stage of change, and both length of stay (LOS) and discharge type among 75 perinatal substance abusers attending a smoke-free residential treatment program. URICA scores predicted LOS (P=.0004) and discharge type (P=.01). Women in action and maintenance remained in treatment longer and were more likely to complete treatment compared to those in precontemplation. Findings were not accounted for by addiction severity. Women with little interest in quitting smoking may have difficulty adhering to smoking restrictions during treatment for other drug problems, resulting in increased attrition. Alternatively, smoking stage of change may be a "proxy" for overall readiness to change in this population.