Developmental changes in genetic and shared environmental contributions to smoking initiation and subsequent smoking quantity in adolescence and young adulthood

Background Few studies examining the genetic architecture of cigarette smoking have focused on adolescents or examined developmental changes in additive genetic, shared environment and unique environmental influences on liability to initiate cigarette smoking and quantity of cigarettes smoked. The aim of this study is to add to the literature on liability to initiate and use cigarettes during adolescence using a nationally representative sample. Method Data for this study came from adolescent and young adult twin pairs (ages 14-33) from the National Longitudinal Study of Adolescent to Adult Health. We ran a series of developmental causal-contingent-common pathway models to examine whether additive genetic, shared and unique environmental influences on liability to the initiation of cigarette use are shared with those on smoking quantity, and whether their contributions change across development. Results We found evidence for a developmental shift in genetic and shared environmental contributions to cigarette use. Early in adolescence genetic and environmental influences work independently on liability to cigarette smoking initiation and quantity of cigarettes smoked, but liability to these behaviors becomes correlated as individuals age into young adulthood. Conclusions These findings provide insight into the causal processes underlying the liability to smoke cigarettes. With age, there is greater overlap in the genetic and environmental factors that influence the initiation of cigarette smoking and quantity of cigarettes smoked

Extended twin study of alcohol use in Virginia and Australia

Drinking alcohol is a normal behavior in many societies, and prior studies have demonstrated it has both genetic and environmental sources of variation. Using two very large samples of twins and their first-degree relatives (Australia ≈ 20,000 individuals from 8,019 families; Virginia ≈ 23,000 from 6,042 families), we examine whether there are differences: (1) in the genetic and environmental factors that influence four interrelated drinking behaviors (quantity, frequency, age of initiation, and number of drinks in the last week), (2) between the twin-only design and the extended twin design, and (3) the Australian and Virginia samples. We find that while drinking behaviors are interrelated, there are substantial differences in the genetic and environmental architectures across phenotypes. Specifically, drinking quantity, frequency, and number of drinks in the past week have large broad genetic variance components, and smaller but significant environmental variance components, while age of onset is driven exclusively by environmental factors. Further, the twin-only design and the extended twin design come to similar conclusions regarding broad-sense heritability and environmental transmission, but the extended twin models provide a more nuanced perspective. Finally, we find a high level of similarity between the Australian and Virginian samples, especially for the genetic factors. The observed differences, when present, tend to be at the environmental level. Implications for the extended twin model and future directions are discussed

Cross-cultural comparison of genetic and cultural transmission of smoking initiation using an extended twin kinship model

Background: Considerable evidence from twin and adoption studies indicates that genetic and shared environmental factors play a role in the initiation of smoking behavior. Although twin and adoption designs are powerful to detect genetic and environmental influences, they do not provide information on the processes of assortative mating and parent–offspring transmission and their contribution to the variability explained by genetic and/or environmental factors. Methods: We examined the role of genetic and environmental factors in individual differences for smoking initiation (SI) using an extended kinship design. This design allows the simultaneous testing of additive and non-additive genetic, shared and individual-specific environmental factors, as well as sex differences in the expression of genes and environment in the presence of assortative mating and combined genetic and cultural transmission, while also estimating the regression of the prevalence of SI on age. A dichotomous lifetime ‘ever’ smoking measure was obtained from twins and relatives in the ‘Virginia 30,000’ sample and the ‘Australian 25,000’. Results: Results demonstrate that both genetic and environmental factors play a significant role in the liability to SI. Major influences on individual differences appeared to be additive genetic and unique environmental effects, with smaller contributions from assortative mating, shared sibling environment, twin environment, cultural transmission, and resulting genotype-environment covariance. Age regression of the prevalence of SI was significant. The finding of negative cultural transmission without dominance led us to investigate more closely two possible mechanisms for the lower parent–offspring correlations compared to the sibling and DZ twin correlations in subsets of the data: (1) age × gene interaction, and (2) social homogamy. Neither of the mechanism provided a significantly better explanation of the data. Conclusions: This study showed significant heritability, partly due to assortment, and significant effects of primarily non-parental shared environment on liability to SI

Prevalence of Nicotine Delivery Systems by Biological Sex in the Spit for Science Study

Nicotine intake usage trends have changed over recent decades given the wide variety of nicotine delivery systems including cigarettes, vaping, hookah, and snubs/chewables. These trends also vary by demographic factors, such as race/ethnicity, sex, and socioeconomic status (SES). For example, studies in rat populations, as well as humans, have found that females tend to be more dependent on nicotine products and have a more difficult time quitting than male rats and humans (Pogun et al., 2017). Also, race/ethnicity may impact the frequency of nicotine usage in different populations; in that non-white Hispanics were more susceptible to smoking through adolescence with a peak at ages 12 and 16; whereas non-Hispanic Asian Americans were less susceptible to smoking at ages 11 and 15 (El-Toukhy et al., 2016). Certain nicotine delivery methods may be more available or perhaps more socially accepted by certain groups of people. While lower SES is associated with more prevalent cigarette advertisements and usage, individuals with a higher SES were associated with an increased prevalence of e-cigarette advertisements, leading to an increased frequency of e-cigarette usage among adolescents (Simon et al., 2018). This project aims to document rates of nicotine use across different nicotine delivery systems in college students by demographic factors. We use the Spit for Science (S4S) database to investigate prevalence rates and study if they differ by sex, race/ethnicity, or SES. It is hypothesized that higher SES individuals will have an increased frequency of use with nicotine products that are non-cigarette based, non-white Hispanics will have greater frequency with nicotine usage, and females within the study sample will display a higher dependency on nicotine products than males. Preliminary analyses reveal that there are more female participants than males throughout the S4S cohorts collected between 2020 and 2022. Across cohorts, prevalence of all nicotine delivery systems differs in female and male participants across all products. Larger differences in prevalence between females and males are observed for cigarettes, smokeless tobacco, and cigars than for products that have been introduced more recently, such as hookah, vaping, and heat-not-burn products. Further analyses will focus on patterns of use in relation to race/ethnicity and SES. Understanding nicotine usage trends within our sample could pave the way for additional research (i.e., genetic studies) and allow for the development of prevention/intervention models tailored to our sample populations.https://scholarscompass.vcu.edu/uresposters/1436/thumbnail.jp

An investigation of weight suppression in a population-based sample of female twins

Weight suppression (WS), maintaining a body weight below one’s maximum adult weight, is associated with bingeing, purging and weight gain in clinical samples

Genetic and environmental variation in continuous phenotypes in the ABCD Study®

Twin studies yield valuable insights into the sources of variation, covariation and causation in human traits. The ABCD Study® (abcdstudy.org) was designed to take advantage of four universities known for their twin research, neuroimaging, population-based sampling, and expertise in genetic epidemiology so that representative twin studies could be performed. In this paper we use the twin data to: (i) provide initial estimates of heritability for the wide range of phenotypes assessed in the ABCD Study using a consistent direct variance estimation approach, assuring that both data and methodology are sound; and (ii) provide an online resource for researchers that can serve as a reference point for future behavior genetic studies of this publicly available dataset. Data were analyzed from 772 pairs of twins aged 9-10 years at study inception, with zygosity determined using genotypic data, recruited and assessed at four twin hub sites. The online tool provides twin correlations and both standardized and unstandardized estimates of additive genetic, and environmental variation for 14,500 continuously distributed phenotypic features, including: structural and functional neuroimaging, neurocognition, personality, psychopathology, substance use propensity, physical, and environmental trait variables. The estimates were obtained using an unconstrained variance approach, so they can be incorporated directly into meta-analyses without upwardly biasing aggregate estimates. The results indicated broad consistency with prior literature where available and provided novel estimates for phenotypes without prior twin studies or those assessed at different ages. Effects of site, self-identified race/ethnicity, age and sex were statistically controlled. Results from genetic modeling of all 53,172 continuous variables, including 38,672 functional MRI variables, will be accessible via the user-friendly open-access web interface we have established, and will be updated as new data are released from the ABCD Study. This paper provides an overview of the initial results from the twin study embedded within the ABCD Study, an introduction to the primary research domains in the ABCD study and twin methodology, and an evaluation of the initial findings with a focus on data quality and suitability for future behavior genetic studies using the ABCD dataset. The broad introductory material is provided in recognition of the multidisciplinary appeal of the ABCD Study. While this paper focuses on univariate analyses, we emphasize the opportunities for multivariate, developmental and causal analyses, as well as those evaluating heterogeneity by key moderators such as sex, demographic factors and genetic background