Highlights • Genetically informative study of racial differences in cigarette use heritability. • Similar influence of genes and environment on cigarette use by race in adolescence. • Genes confer ...risk in White adults but African Americans environments also important.
Nicotine dependence and smoking quantity are both robustly associated with the
CHRNA5-A3-B4
gene cluster in the 15q25 region, and SNP rs16969968 in particular. The purpose of this paper is to use ...structural equation modeling techniques (SEM) to disentangle the complex pattern of relationships between rs16969968, nicotine quantity (as measured by the number of cigarettes an individual smokes per day; CPD) and nicotine dependence (as measured by the Fagerström Test for Nicotine Dependence; FTND). CPD is an indicator, but also a potential cause, of FTND, complicating the interpretation of associations between these constructs and requires a more detailed investigation than standard GWAS or general linear regression models can provide. FTND items and genotypes were collected in four samples, with a combined sample size of 5,373 respondents. A mega-analysis was conducted using a multiple group SEM approach to test competing hypotheses regarding the relationships between the SNP rs16969968, FTND and CPD. In the best fitting model, the FTND items loaded onto two correlated factors. The first, labeled “maintenance,” assesses the motivation to maintain constant levels of nicotine through out the day. The second was labeled “urgency” as its items concern the urgency to restore nicotine levels after abstinence. We focus our attention on the “maintenance” factor, of which CPD was an indicator. The best fitting model included a negative feedback loop between the Maintenance factor and CPD. Accordingly, the motivation to maintain higher levels of nicotine increased the quantity of nicotine consumed, which subsequently decreases the maintenance motivation. The fact that the Maintenance-CPD feedback model fits the data best implies that there are at least two biological pathways that lead from rs16969968 to smoking behaviors. The model is consistent with a supply and demand system, which allows individuals to achieve a homeostatic equilibrium for their nicotine concentration.
Chronic cigarette use has been consistently associated with differences in the neuroanatomy of smokers relative to nonsmokers in case–control studies. However, the etiology underlying the ...relationships between brain structure and cigarette use is unclear. A community-based sample of male twin pairs ages 51–59 (110 monozygotic pairs, 92 dizygotic pairs) was used to determine the extent to which there are common genetic and environmental influences between brain structure and average lifetime cigarette use. Brain structure was measured by high-resolution structural magnetic resonance imaging, from which subcortical volume and cortical volume, thickness and surface area were derived. Bivariate genetic models were fitted between these measures and average lifetime cigarette use measured as cigarette pack-years. Widespread, negative phenotypic correlations were detected between cigarette pack-years and several cortical as well as subcortical structures. Shared genetic and unique environmental factors contributed to the phenotypic correlations shared between cigarette pack-years and subcortical volume as well as cortical volume and surface area. Brain structures involved in many of the correlations were previously reported to play a role in specific aspects of networks of smoking-related behaviors. These results provide evidence for conducting future research on the etiology of smoking-related behaviors using measures of brain morphology.
The genetic basis of political sophistication Arceneaux, Kevin; Johnson, Martine; Maes, Hermine H
Twin research and human genetics,
02/2012, Letnik:
15, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Political sophistication is a concept that encompasses political reasoning, the coherence of people's issue attitudes, and their knowledge of political processes. To what extent is political ...sophistication affected by genes and environments? Do these distinct but related measures of sophistication share a common genetic structure? We analyze survey data collected from participants in the Minnesota Twin Registry to estimate influences of genes and environments on variables used to measure political sophistication. Additive genetic factors explain 48-76% of the variation in educational attainment, political interest, and political knowledge, while dominance genetics influence 28% of the variance of ideological consistency. Multivariate analyses show that, although these measures share common genetic and unique environmental factors to a modest extent, much of the variance is explained by specific genetic and unique environmental factors. Ideological consistency appears to be mostly distinct from the other measures, as it is strongly accounted for by unique environmental influences.
Background
Great variability exists in response to stressful or traumatic events, leading to an interest in the construct of resilience as a trait and an outcome. The etiologic sources of variability ...across differing conceptualizations of resilience are poorly understood.
Methods
Using behavioral genetic methods in a sample of 2,056 female twins, the present study sought to (a) examine the etiologic sources of a trait‐based self‐report measure of perceived resilience (PR), (b) determine the genetic and environmental overlap with an outcome‐based measure of resilience, as defined by the absence of psychiatric symptoms after stressful life events, previously used by our research team (discrepancy‐based psychiatric resilience DBPR), and (c) determine the etiologic overlap of these two resilience measures with major depressive disorder (MDD).
Results
PR was modestly (11%) heritable. A moderate degree of genetic overlap (39%) and a nominal amount of environmental overlap (3%) were found between the two alternative measures of resilience. Genetic factors that influence PR accounted for 3% of MDD heritability, whereas 31% of MDD heritability was due to DBPR genetic factors.
Conclusions
Findings of a higher genetic correlation between the outcome‐based resilience measure and MDD compared to the trait‐based measure and MDD suggest gene‐finding efforts may benefit from considering the multifaceted nature of resilience and that resilience is best understood as both a phenotypically and genetically heterogeneous construct.
Illicit substance use is dangerous in both acute and chronic forms, frequently resulting in lethal poisoning, addiction, and other negative consequences. Similar to research in other psychiatric ...conditions, whose ultimate goal is to enable effective prevention and treatment, studies in substance use are focused on factors elevating the risk for the disorder. The rapid growth of the substance use problem despite the effort invested in fighting it, however, suggests the need in changing the research approach. Instead of attempting to identify risk factors, whose neutralization is often infeasible if not impossible, it may be more promising to systematically reverse the perspective to the factors enhancing the aspect of liability to disorder that shares the same dimension but is opposite to risk, that is, resistance to substance use. Resistance factors, which enable the majority of the population to remain unaffected despite the ubiquity of psychoactive substances, may be more amenable to translation. While the resistance aspect of liability is symmetric to risk, the resistance approach requires substantial changes in sampling (high-resistance rather than high-risk) and using quantitative indices of liability. This article provides an overview and a practical approach to research in resistance to substance use/addiction, currently implemented in a NIH-funded project. The project benefits from unique opportunities afforded by the data originating from two longitudinal twin studies, the Virginia Twin Study of Adolescent and Behavioral Development and the Minnesota Twin Family Study. The methodology described is also applicable to other psychiatric disorders.
As the use of electronic cigarette (EC) continues to rise in the United States, especially among adolescents and young adults, it is necessary to better understand the factors associated with EC ...initiation. Specifically, it is unclear how genetic and environmental contributions influence the initiation of EC. Furthermore, the degree to which genetic and environmental influences are shared between EC initiation and conventional cigarette (CC) initiation is unknown.
A sample of young adult twins ages 15-20 (N = 858 individuals; 421 complete twin pairs) was used to estimate the genetic and environmental influences on the liability of initiation unique to EC and CC as well as the degree to which these factors are shared between the two. Approximately 24% of participants initiated the use of EC, 19% initiated the use of CC, and 11% initiated the dual use.
Combined contributions of additive genetic and shared environmental influences were significant for CC (ACC = 0.19 95% confidence interval {CI} = 0-0.79, p = 0.57; CCC = 0.42 95% CI = 0-0.70, p = 0.13) and EC (AEC = 0.25 95% CI = 0-0.83, p = 0.44; CEC = 0.42 95% CI = 0-0.73, p = 0.12), whereas unique environmental influences were significant (ECC = 0.39 95% CI = 0.18-0.57, p < 0.001; EEC = 0.32 95% CI = 0.14-0.56, p < 0.001). Results also demonstrated a significant overlap of the unique environmental (rE = 0.87, p < 0.001) and familial influences contributing to correlation between the two phenotypes in the bivariate analysis.
These preliminary results suggest that both genes and environmental influences are potential drivers of EC initiation among adolescents and young adults.
This article is the first to use a sample of twin to estimate the contributions of genetic and environmental influences toward EC initiation and estimate the potential for overlapping influences with CC initiation. This study has implications for future debate about the etiology of EC and CC use with respect to potential overlapping genetic and environmental influences.
Background and Aims
Electronic cigarette use has escalated rapidly in recent years, particularly among youth. Little is known about the genetic influences on e‐cigarette use. This study aimed to ...determine whether genetic risk for regular use of combustible cigarettes or for number of cigarettes smoked per day confers risk for ever e‐cigarette use or frequency of e‐cigarette use.
Design, Setting, Participants, and Measurements
We used data from 9541 young adults from the Spit for Science longitudinal cohort study (2011–2019). Polygenic scores (PGS) of regular combustible cigarette use (PGS‐RCU) and cigarettes per day (PGS‐CPD) were constructed using summary statistics from the two largest available genome‐wide association study (GWAS) meta‐analysis of European ancestry and East Asian ancestry of combustible cigarette use and used to test whether the PGS of RCU or CPD predicted lifetime e‐cigarette use and frequency of past 30‐day e‐cigarette use in a diverse sample of young adults of African (AFR), Admixed American (AMR), East Asian (EAS), European (EUR), and South Asian (SAS) ancestry.
Findings
The PGS‐RCU was associated with lifetime e‐cigarette use in the EUR sample (OR = 1.27, 95% CI = 1.19–1.36, P = 7.53 × 10−12), but not in the other subsamples (ps > 0.12). This association remained significant after excluding regular combustible cigarette smokers (OR = 1.21, 95% CI = 1.12–1.31, P = 3.36 × 10−6). There was no statistically significant association between PGS‐CPD and lifetime e‐cigarette use and neither the PGS‐RCU nor the PGS‐CPD were associated with frequency of e‐cigarette use in the past 30 days in any of the subsamples.
Conclusions
Genetic factors associated with regular combustible cigarette use appear to be associated with ever e‐cigarette use in young adults. We did not find evidence for shared genetic factors influencing heaviness of use of combustible cigarettes and current e‐cigarette use frequency.
Cross-lagged panel models (CLPMs) are commonly used to estimate causal influences between two variables with repeated assessments. The lagged effects in a CLPM depend on the time interval between ...assessments, eventually becoming undetectable at longer intervals. To address this limitation, we incorporate instrumental variables (IVs) into the CLPM with two study waves and two variables. Doing so enables estimation of both the lagged (i.e., "distal") effects and the bidirectional cross-sectional (i.e., "proximal") effects at each wave. The distal effects reflect Granger-causal influences across time, which decay with increasing time intervals. The proximal effects capture causal influences that accrue over time and can help infer causality when the distal effects become undetectable at longer intervals. Significant proximal effects, with a negligible distal effect, would imply that the time interval is too long to estimate a lagged effect at that time interval using the standard CLPM. Through simulations and an empirical application, we demonstrate the impact of time intervals on causal inference in the CLPM and present modeling strategies to detect causal influences regardless of the time interval in a study. Furthermore, to motivate empirical applications of the proposed model, we highlight the utility and limitations of using genetic variables as IVs in large-scale panel studies.
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