Genetic interactions with prenatal social environment: effects on academic and behavioral outcomes

Exploring the Fetal Origins Hypothesis Using Genetic Data

Birth weight is a robust predictor of valued life course outcomes, emphasizing the importance of prenatal development. But does birth weight act as a proxy for environmental conditions in utero, or do biological processes surrounding birth weight themselves play a role in healthy development? To answer this question, we leverage variation in birth weight that is, within families, orthogonal to prenatal environmental conditions: one's genes. We construct polygenic scores in two longitudinal studies (Born in Bradford, N = 2008; Wisconsin Longitudinal Study, N = 8488) to empirically explore the molecular genetic correlates of birth weight. A 1 standard deviation increase in the polygenic score is associated with an ~100-grams increase in birth weight and a 1.4 pp (22 percent) decrease in low birth weight probability. Sibling comparisons illustrate that this association largely represents a causal effect. The polygenic score-birth weight association is increased for children who spend longer in the womb and whose mothers have higher body mass index, though we find no differences across maternal socioeconomic status. Finally, the polygenic score affects social and cognitive outcomes, suggesting that birth weight is itself related to healthy prenatal development.

Genetic predispositions moderate the effectiveness of tobacco excise taxes

BACKGROUND

Tobacco consumption is one of the leading causes of preventable death. In this study, we analyze whether someone's genetic predisposition to smoking moderates the response to tobacco excise taxes.

METHODS

We interact polygenic scores for smoking behavior with state-level tobacco excise taxes in longitudinal data (1992-2016) from the US Health and Retirement Study (N = 12,058).

RESULTS

Someone's genetic propensity to smoking moderates the effect of tobacco excise taxes on smoking behavior along the extensive margin (smoking vs. not smoking) and the intensive margin (the amount of tobacco consumed). In our analysis sample, we do not find a significant gene-environment interaction effect on smoking cessation.

CONCLUSIONS

When tobacco excise taxes are relatively high, those with a high genetic predisposition to smoking are less likely (i) to smoke, and (ii) to smoke heavily. While tobacco excise taxes have been effective in reducing smoking, the gene-environment interaction effects we observe in our sample suggest that policy makers could benefit from taking into account the moderating role of genes in the design of future tobacco control policies.

Biology and American Sociology, Part II: Developing a Unique Evolutionary Sociology

In sociology's formative period between 1830 and 1930, evolutionary analysis organized much theorizing and research. This line of work ended abruptly in the 1920s but, over the last decades, has come back into the discipline somewhat piecemeal with the reintroduction of more sophisticated stage models of societal evolution, functional analysis, human ecological analysis, and other new lines of evolutionary inquiry outlined in this paper. Our goal is to demonstrate that revitalized paradigms of the past can still be useful with modest reconceptualization, while at the same time new intellectual movements in the other social sciences, especially economics and psychology, incorporating evolutionary ideas from biology provide sociology with an opportunity to develop its own approach to evolutionary analysis that avoids the problems that let to the demise of this line of inquiry in the 1920s, as well as the problems of other social sciences applying their more narrowly focus models to sociological problems. Indeed, sociology can become a leader in the social sciences in developing more sophisticated theoretical and methodological approaches to incorporating biology and evolutionary analysis into the social sciences. When presented in a new, more sophisticated guise, old approaches like functionalism, stage models of societal evolution, and ecological models can be seen as still having a great deal of explanatory power, while revealing a progressive and future orientation that should appeal to all contemporary sociologists. It is time, then, for sociology to remember its past in order to move into the future.

Genetic architecture of socioeconomic outcomes: Educational attainment, occupational status, and wealth

This study takes a socio-genomic approach to examine the complex relationships among three important socioeconomic outcomes: educational attainment, occupational status, and wealth. Using more than 8,000 genetic samples from the Health and Retirement study, it first estimates the collective influence of genetic variants across the whole human genome to each of the three socioeconomic outcomes. It then tests genetic correlations among three socioeconomic outcomes, and examines the extent to which genetic influences on occupational status and wealth are mediated by educational attainment. Analyses using the genomic-relatedness-matrix restricted maximum likelihood method show significant genetic correlations among the three outcomes, and provide evidence for both mediated and independent genetic influences. A polygenic score analysis demonstrates the utility of findings in socio-genomic studies to address genetic confounding in causal relationships among the three socioeconomic outcomes.

Does education attenuate the genetic risk of obesity? Evidence from U.K. Twins

More education is associated with a lower body mass index (BMI) and likelihood of being obese. Obesity and BMI also have a strong genetic basis. Given these observations, we investigate whether more education can reduce obesity by attenuating the underlying genetic risk of being obese, through gene-environment (GxE) interactions. We estimate associations between (i) education, (ii) a genetic risk score (GRS) and (iii) GxE interactions between education and the GRS through Ordinary least Squares (OLS) and twins fixed-effect regressions using data on female twins from the TwinsUK database. OLS estimates show that there are significant associations of education and genetics. Female twins with a university education are 14.3 percentage points less likely to be obese compared to twins with less than compulsory education, and a 1 standard deviation increase in the GRS increases the likelihood of being obese by 5.2 percentage points. The GxE interactions are statistically insignificant, suggesting that the marginal association of the GRS with obesity does not differ by educational attainment. When controlling for confounding through twins fixed-effects, we find a smaller role of genetics. The association of the GRS with obesity decreases to 0.040. Associations of educational attainment are substantially reduced and insignificant. GxE interactions also remain insignificant. Overall, we find little evidence of any GxE interactions.

Education, Smoking, and Cohort Change: Forwarding a Multidimensional Theory of the Environmental Moderation of Genetic Effects

We introduce a genetic correlation by environment interaction model [(rG)xE] which allows for social environmental moderation of the genetic relationship between two traits. To empirically demonstrate the significance of the (rG)xE perspective, we use genome wide information from respondents of the Health and Retirement Study (HRS; n = 8,181; birth years 1920-1959) and the National Longitudinal Study of Adolescent to Adult Health (Add Health; n = 4,347; birth years 1974-1983) to examine whether the genetic correlation (rG) between education and smoking has increased over historical time. Genetic correlation estimates (rG_HRS = -0.357; rG_{Add Health} = -0.729) support this hypothesis. Using polygenic scores for educational attainment, we show that this is not due to latent indicators of intellectual capacity, and we highlight the importance of education itself as an explanation of the increasing genetic correlation. Analyses based on contextual variation the milieus of the Add Health respondents corroborate key elements of the birth cohort analyses. We argue that the increasing overlap with respect to genes associated with educational attainment and smoking is a fundamentally social process involving complex process of selection based on observable behaviors that may be linked to genotype.

Plastic and immobile: Unequal intergenerational mobility by genetic sensitivity score within sibling pairs

Contrary to traditional biological arguments, the differential susceptibility model suggests genotype may moderate rather than mediate parent-child economic similarity. Using family fixed effects models of Add Health sibling data, I investigate the relationship between an index of sensitive genotypes and intergenerational mobility. Full, same sex sibling comparisons hold constant parental characteristics and address the non-random distribution of genotype that reduces internal validity in nationally representative samples. Across multiple measures of young adult financial standing, those with more copies of sensitive genotypes achieve lower economic outcomes than their sibling if they are from a low income context but fare better from a high income context. This genetic sensitivity to parental income entails lower intergenerational mobility. Results support the differential susceptibility model and contradict simplistic genetic explanations for intergenerational inequality, suggesting sensitive genotypes are not inherently positive or negative but rather increase dependence on parental income and reduce mobility.

The Influence of Men's Military Service on Smoking Across the Life Course

The military is described as a social context that contributes to the (re-)initiation or intensification of cigarette smoking. We draw on data from the 1985-2014 National Survey of Drug Use and Health (NSDUH) and the Wisconsin Longitudinal Study (WLS) to conduct complementary sub-studies of the influence of military service on men's smoking outcomes across the life course. Descriptive findings from an age-period-cohort analysis of NSDUH data document higher probabilities of current smoking and heavy smoking among veteran men across a broad range of cohorts and at all observed ages. Findings from sibling fixed-effects Poisson models estimated on the WLS data document longer durations of smoking among men who served in the military and no evidence that selection explains the observed relationship. Together, these results provide novel and potentially generalizable evidence that participation in the military in early adulthood exerts a causal influence on smoking across the life course.

Opportunities and challenges of big data for the social sciences: The case of genomic data

In this paper, we draw attention to one unique and valuable source of big data, genomic data, by demonstrating the opportunities they provide to social scientists. We discuss different types of large-scale genomic data and recent advances in statistical methods and computational infrastructure used to address challenges in managing and analyzing such data. We highlight how these data and methods can be used to benefit social science research.

Socio-Genomics and Structural Competency

Adverse developmental exposures and pathologies of the social environment make vastly greater contributions to the leading health burdens in society than currently known genotypic information. Yet, while patients now commonly bring information on single alleles to the attention of their healthcare team, the former conditions are only rarely considered with respect to future health outcomes. This manuscript aims to integrate social environmental influences in genetic predictive models of disease risk. Healthcare providers must be educated to better understand genetic risks for complex diseases and the specific health consequences of societal adversities, to facilitate patient education, disease prevention, and the optimal care in order to achieve positive health outcomes for those with early trauma or other social disadvantage.

Sibling genes as environment: Sibling dopamine genotypes and adolescent health support frequency dependent selection

While research consistently suggests siblings matter for individual outcomes, it remains unclear why. At the same time, studies of genetic effects on health typically correlate variants of a gene with the average level of behavioral or health measures, ignoring more complicated genetic dynamics. Using National Longitudinal Study of Adolescent Health data, we investigate whether sibling genes moderate individual genetic expression. We compare twin variation in health-related absences and self-rated health by genetic differences at three locations related to dopamine regulation and transport to test sibship-level cross-person gene-gene interactions. Results suggest effects of variation at these genetic locations are moderated by sibling genes. Although the mechanism remains unclear, this evidence is consistent with frequency dependent selection and suggests much genetic research may violate the stable unit treatment value assumption.

Peer Influence, Genetic Propensity, and Binge Drinking: A Natural Experiment and a Replication

The authors draw data from the College Roommate Study (ROOM) and the National Longitudinal Study of Adolescent Health to investigate gene-environment interaction effects on youth binge drinking. In ROOM, the environmental influence was measured by the precollege drinking behavior of randomly assigned roommates. Random assignment safeguards against friend selection and removes the threat of gene-environment correlation that makes gene-environment interaction effects difficult to interpret. On average, being randomly assigned a drinking peer as opposed to a nondrinking peer increased college binge drinking by 0.5-1.0 episodes per month, or 20%-40% the average amount of binge drinking. However, this peer influence was found only among youths with a medium level of genetic propensity for alcohol use; those with either a low or high genetic propensity were not influenced by peer drinking. A replication of the findings is provided in data drawn from Add Health. The study shows that gene-environment interaction analysis can uncover social-contextual effects likely to be missed by traditional sociological approaches.

Understanding heterogeneity in the effects of birth weight on adult cognition and wages

A large economics literature has shown long term impacts of birth weight on adult outcomes, including IQ and earnings that are often robust to sibling or twin fixed effects. We examine potential mechanisms underlying these effects by incorporating findings from the genetics and neuroscience literatures. We use a sample of siblings combined with an "orchids and dandelions hypothesis", where the IQ of genetic dandelions is not affected by in utero nutrition variation but genetic orchids thrive under advantageous conditions and wilt in poor conditions. Indeed, using variation in three candidate genes related to neuroplasticity (APOE, BDNF, and COMT), we find substantial heterogeneity in the associations between birth weight and adult outcomes, where part of the population (i.e., "dandelions") is not affected by birth weight variation. Our results help uncover why birth weight affects adult outcomes.

Can education rescue genetic liability for cognitive decline?

Although there is a vast literature linking education and later health outcomes, the mechanisms underlying these associations are relatively unknown. In the spirit of some medical literature that leverages developmental abnormalities to understand mechanisms of normative functioning, we explore the ability of higher educational attainments to "rescue" biological/genetic liabilities in brain function through inheritance of a variant of the APOE gene shown to lead to cognitive decline, dementia, and Alzheimer's disease in old age. Deploying a between-sibling design that allows quasi-experimental variation in genotype and educational attainment within a standard gene-environment interaction framework, we show evidence that the genetic effects of the "risky" APOE variant on old-age cognitive decline are absent in individuals who complete college (vs. high school graduates). Auxiliary analyses suggest that the likely mechanisms of education are most consistent through changing brain processes (i.e., "how we think") and potentially building cognitive reserves, rather than alleviating old age cognitive decline through the channels of higher socioeconomic status and resources over the life course.

Interactive effects of in utero nutrition and genetic inheritance on cognition: new evidence using sibling comparisons

A large literature links early environments and later outcomes, such as cognition; however, little is known about the mechanisms. One potential mechanism is sensitivity to early environments that is moderated or amplified by the genotype. With this mechanism in mind, a complementary literature outside economics examines the interaction between genes and environments, but often problems of endogeneity and bias in estimation are uncorrected. A key issue in the literature is exploring environmental variation that is not exogenous, which is potentially problematic if there are gene-environment correlation or gene-gene interactions. Using sibling pairs with genetic data in the Wisconsin Longitudinal Study we extend a previous, and widely cited, gene-environment study that explores an interaction between the FADS2 gene, which is associated with the processing of essential fatty acids related to cognitive development, and early life nutrition in explaining later-life IQ. Our base OLS findings suggest that individuals with specific FADS2 variants gain roughly 0.15 standard deviations in IQ for each standard deviation increase in birth weight, our measure of the early nutrition environment; while, individuals with other variants of FADS2 do not have a statistically significant association with early nutrition, implying the genotype is influencing the effects of environmental exposure. When including family-level fixed effects, however, the magnitude of the gene-environment interaction is reduced by half and statistical significance dissipates, implying the interaction between FADS2 and early nutrition in explaining later life IQ may in part be due to unobserved, family-level factors. The example has wider implications for the practice of investigating gene-environment interactions when the environmental exposure is not exogenous and robustness to unobserved variation in the genome is not controlled for in the analysis.

The long arm of adolescence: school health behavioral environments, tobacco and alcohol co-use, and the 5HTTLPR gene

Although sociologists, demographers, and others have thoroughly studied contextual and life course influences on tobacco and alcohol use in adolescence and young adulthood, far less attention has been paid to the determinants of tobacco and alcohol co-use. This is important to remedy because co-use has a nonadditive effect on long-term health. In this article, we use nationally representative, longitudinal data from adolescents and young adults to examine patterns of joint tobacco and alcohol use behaviors across the life course. Importantly, we describe how these trajectories are linked to respondents' high school's joint profile of tobacco and alcohol use, measured two ways: as the proportion of tobacco and alcohol co-users, and as the "excess proportion" above that expected based on the marginal probabilities of smoking and drinking in that school. Joint tobacco and alcohol use is associated with both measures, emphasizing the "long arm" of adolescent contexts. Furthermore, we extend previous research to assess whether there is a gene-environment interaction between this school-level measure, 5HTTLPR, and tobacco and alcohol co-use, as suggested by recent work analyzing drinking and smoking separately. We find evidence of such a pattern but conclude that it is likely to be due to population stratification or other forms of confounding.

Critical need for family-based, quasi-experimental designs in integrating genetic and social science research

Researchers have identified environmental risks that predict subsequent psychological and medical problems. Based on these correlational findings, researchers have developed and tested complex developmental models and have examined biological moderating factors (e.g., gene-environment interactions). In this context, we stress the critical need for researchers to use family-based, quasi-experimental designs when trying to integrate genetic and social science research involving environmental variables because these designs rigorously examine causal inferences by testing competing hypotheses. We argue that sibling comparison, offspring of twins or siblings, in vitro fertilization designs, and other genetically informed approaches play a unique role in bridging gaps between basic biological and social science research. We use studies on maternal smoking during pregnancy to exemplify these principles.

Heritability and the equal environments assumption: evidence from multiple samples of misclassified twins

Classically derived estimates of heritability from twin models have been plagued by the possibility of genetic-environmental covariance. Survey questions that attempt to measure directly the extent to which more genetically similar kin (such as monozygotic twins) also share more similar environmental conditions represent poor attempts to gauge a complex underlying phenomenon of GE-covariance. The present study exploits a natural experiment to address this issue: Self-misperception of twin zygosity in the National Longitudinal Survey of Adolescent Health (Add Health). Such twins were reared under one "environmental regime of similarity" while genetically belonging to another group, reversing the typical GE-covariance and allowing bounded estimates of heritability for a range of outcomes. In addition, we examine twins who were initially misclassified by survey assignment--a stricter standard--in three datasets: Add Health, the Minnesota Twin Family Study and the Child and Adolescent Twin Study in Sweden. Results are similar across approaches and datasets and largely support the validity of the equal environments assumption.