Integrating genetics and social science: genetic risk scores

Genetic nature or genetic nurture? Introducing social genetic parameters to quantify bias in polygenic score analyses

Results from a genome-wide association study (GWAS) can be used to generate a polygenic score (PGS), an individual-level measure summarizing identified genetic influence on a trait dispersed across the genome. For complex, behavioral traits, the association between an individual's PGS and their phenotype may contain bias (from geographic, ancestral, and/or socioeconomic confounding) alongside the causal effect of the individual's genes. We formalize the introduction of a different source of bias in regression models using PGSs: the effects of parental genes on offspring outcomes, known as genetic nurture. GWAS do not discriminate between the various pathways through which genes become associated with outcomes, meaning existing PGSs capture both direct genetic effects and genetic nurture effects. We construct a theoretical model for genetic effects and show that the presence of genetic nurture biases PGS coefficients from both naïve OLS (between-family) and family fixed effects (within-family) regressions. This bias is in opposite directions; while naïve OLS estimates are biased away from zero, family fixed effects estimates are biased toward zero. We quantify this bias using two novel parameters: (1) the genetic correlation between the direct and nurture effects and (2) the ratio of the SNP heritabilities for the direct and nurture effects.

Geographic Clustering of Polygenic Scores at Different Stages of the Life Course

We interrogate state-level clustering of polygenic scores at different points in the life course and variation in the association of mean polygenic scores in a respondent's state of birth with corresponding phenotypes. The polygenic scores for height and smoking show the most state-level clustering (2 to 4 percent) with relatively little clustering observed for the other scores. However, even the small amounts of observed clustering are potentially meaningful. The state-mean polygenic score for educational attainment is strongly associated with an individual's educational attainment net of that person's polygenic score. The ecological clustering of polygenic scores may denote a new environmental factor in gene-environment research. We conclude by discussing possible mechanisms that underlie this association and the implications of our findings for social and genetic research.

The Effect of Vietnam-Era Conscription and Genetic Potential for Educational Attainment on Schooling Outcomes

This study examines whether draft lottery estimates of the causal effects of Vietnam-era military service on schooling vary by an individual's genetic propensity toward educational attainment. To capture the complex genetic architecture that underlies the bio-developmental pathways, behavioral traits and evoked environments associated with educational attainment, we construct polygenic scores (PGS) for respondents in the Health and Retirement Study (HRS) that aggregate thousands of individual loci across the human genome and weight them by effect sizes derived from a recent genome-wide association study (GWAS) of years of education. Our findings suggest veterans with below average PGSs for educational attainment may have completed fewer years of schooling than comparable non-veterans. On the other hand, we do not find any difference in the educational attainment of veterans and non-veterans with above average PGSs. Results indicate that public policies and exogenous environments may induce heterogeneous treatment effects by genetic disposition.

Parenting and adolescents' psychological adjustment: Longitudinal moderation by adolescents' genetic sensitivity

We examined whether adolescents' genetic sensitivity, measured by a polygenic index score, moderated the longitudinal associations between parenting and adolescents' psychological adjustment. The sample included 323 mothers, fathers, and adolescents (177 female, 146 male; Time 1 [T1] average age = 12.61 years, SD = 0.54 years; Time 2 [T2] average age = 13.59 years, SD = 0.59 years). Parents' warmth and hostility were rated by trained, independent observers using videotapes of family discussions. Adolescents reported their symptoms of anxiety, depressed mood, and hostility at T1 and T2. The results from autoregressive linear regression models showed that adolescents' genetic sensitivity moderated associations between observations of both mothers' and fathers' T1 parenting and adolescents' T2 composite maladjustment, depression, anxiety, and hostility. Compared to adolescents with low genetic sensitivity, adolescents with high genetic sensitivity had worse adjustment outcomes when parenting was low on warmth and high on hostility. When parenting was characterized by high warmth and low hostility, adolescents with high genetic sensitivity had better adjustment outcomes than their counterparts with low genetic sensitivity. The results support the differential susceptibility model and highlight the complex ways that genes and environment interact to influence development.

Invited Commentary: Integrating Genomics and Social Epidemiology-Analysis of Late-Life Low Socioeconomic Status and the Conserved Transcriptional Response to Adversity

Socially disadvantaged children face increased morbidity and mortality as they age. Understanding mechanisms through which social disadvantage becomes biologically embedded and devising measurements that can track this embedding are critical priorities for research to address social gradients in health. The analysis by Levine et al. (Am J Epidemiol. 2017;186(5):503-509) of genome-wide gene expression in a subsample of US Health and Retirement Study participants suggests important new directions for the field. Specifically, findings suggest promise in integrating gene expression data into population studies and provide further evidence for the conserved transcriptional response to adversity as a marker of biological embedding of social disadvantage. The study also highlights methodological issues related to the analysis of gene expression data and social gradients in health and a need to examine the conserved transcriptional response to adversity alongside other proposed measurements of biological embedding. Looking to the future, advances in genome science are opening new opportunities for sociogenomic epidemiology.

Comparing distributions of polygenic risk scores of type 2 diabetes and coronary heart disease within different populations

Polygenic risk scores are gaining more and more attention for estimating genetic risks for liabilities, especially for noncommunicable diseases. They are now calculated using thousands of DNA markers. In this paper, we compare the score distributions of two previously published very large risk score models within different populations. We show that the risk score model together with its risk stratification thresholds, built upon the data of one population, cannot be applied to another population without taking into account the target population’s structure. We also show that if an individual is classified to the wrong population, his/her disease risk can be systematically incorrectly estimated.

Environmental risks outweigh dopaminergic genetic risks for alcohol use and abuse from adolescence through early adulthood

BACKGROUND

Alcohol use is a primary public health concern, particularly among adolescents and young adults. Based on the rapidly growing field of gene-environment models, this study assessed the combined role of environmental and dopamine-related genetic correlates of early alcohol use and abuse.

METHODS

Multilevel growth models assessed trajectories of alcohol use and intoxication and ordered logistic regressions assessed alcohol use disorder among a sample of 12,437 youth from the nationally representative Add Health study who were followed from mid-adolescence through early adulthood.

RESULTS

Endogenous and exogenous stressful life events and social norms supportive of alcohol use from parents and peers were significant predictors of alcohol use, intoxication, and alcohol use disorder, with consistent patterns across males and females. In contrast, a dopamine-system genetic risk score (GRS) was not associated with alcohol use trajectories nor alcohol use disorder in early adulthood, although weak connections emerged between the GRS and growth trajectories of intoxication, indicating that higher GRS predicted more frequent episodes of intoxication during the transition to adulthood but not during adolescence or later 20s. No evidence of gene-environment interactions emerged.

CONCLUSIONS

Results extend a substantial body of prior research primarily assessing single genetic polymorphisms in the dopamine system, suggesting that dopaminergic GRSs may be associated with more problematic alcohol behaviors at some developmental periods, but further, that social norms and stressful life experiences are more consistent correlates of early and problematic alcohol use among youth. These environmental factors present potential targets for research manipulating contexts to identify causal pathways.

Effects of bonding with parents and home culture on intercultural adaptations and the moderating role of genes

In the current age of globalization, living abroad is becoming an increasingly common and highly sought after experience. Sojourners' ability to adjust to a new culture can be affected by their existing attachments, internalized as intrapsychic environment, as well as their biological sensitivity to environment. This sensitivity can be partly attributed to one's genomic endowments. As such, this prospective study sought to examine the differential effects of early experiences with parents and affection for home culture on young adults' ability to adapt to a foreign culture (n=305, students who studied overseas for a semester) - specifically, the difficulties they experience - moderated by genetic susceptibility. An additional 258 students who did not travel overseas were included as a comparison group to demonstrate the uniqueness of intercultural adaptation. Current findings suggest that the maternal, paternal and cultural bondings or affections affect different aspects of intercultural adjustment. Maternal bonding affected sojourners' relationships with host nationals, while paternal bonding affected sojourners' adjustment to a new physical environment. Moreover, individuals' genetic predispositions significantly moderate these main effects regarding how much difficulty the sojourners experienced overseas.

Genetic endowments, parental resources and adult health: Evidence from the Young Finns Study

This paper uses longitudinal survey data linked to administrative registers to examine socioeconomic gradients in health, particularly whether the effects of genetic endowments interact with the socioeconomic resources of the parental household. We find that genetic risk scores contribute to adult health measured by biomarkers. This result is consistent with the findings from genome-wide association studies. Socioeconomic gradients in health differ based on biomarker and resource measures. Family education is negatively related to obesity and the waist-hip ratio, and family income is negatively related to low-density lipoprotein cholesterol and triglyceride levels. Parental resources do not modify the effects of genetic endowment on adult health. However, there is evidence for gene-family income interactions for triglyceride levels, particularly among women.

Peer Problems and Hyperactivity-Impulsivity Among Norwegian and American Children: The Role of 5-HTTLPR

Peer problems are linked to attention deficit hyperactivity disorder (ADHD) symptoms and the serotonin system is thought to be involved in ADHD-related behavior. Hence, from a Gene × Environment perspective, the serotonin transporter 5-HTTLPR may play a moderating role. In two large community samples, the moderating role of 5-HTTLPR was examined related to more hyperactivity-impulsivity symptoms (HI symptoms) predicted by more peer problems. In Study 1, involving 642 Norwegian children, results indicated that for s-allele carriers only, caregiver-reported peer problems at age 4 predicted more parent-reported HI symptoms at age 6. In Study 2, similar results emerged involving 482 American children. Discussion focuses on differential sensitivity to the adverse effects of poor peer relations.

Genes, behavior, and behavior genetics

According to the 'first law' of behavior genetics, 'All human behavioral traits are heritable.' Accepting the validity of this first law and employing statistical methods, researchers within psychology, sociology, political science, economics, and business claim to have demonstrated that all the behaviors studied by their disciplines are heritable-no matter how culturally specific these behaviors appear to be. Further, in many cases they claim to have identified specific genes that play a role in those behaviors. The validity of behavior genetics as a discipline depends upon the validity of the research methods used to justify such claims. It also depends, foundationally, upon certain key assumptions concerning the relationship between genotype (one's specific DNA sequences) and phenotype (any and all observable traits or characteristics). In this article, I examine-and find serious flaws with-both the methodologies of behavior genetics and the underlying assumptions concerning the genotype-phenotype relationship. WIREs Cogn Sci 2017, 8:e1405. doi: 10.1002/wcs.1405 For further resources related to this article, please visit the WIREs website.

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.

Changing Polygenic Penetrance on Phenotypes in the 20(th) Century Among Adults in the US Population

This study evaluates changes in genetic penetrance—defined as the association between an additive polygenic score and its associated phenotype—across birth cohorts. Situating our analysis within recent historical trends in the U.S., we show that, while height and BMI show increasing genotypic penetrance over the course of 20^th Century, education and heart disease show declining genotypic effects. Meanwhile, we find genotypic penetrance to be historically stable with respect to depression. Our findings help inform our understanding of how the genetic and environmental landscape of American society has changed over the past century, and have implications for research which models gene-environment (GxE) interactions, as well as polygenic score calculations in consortia studies that include multiple birth cohorts.

The Bell Curve Revisited: Testing Controversial Hypotheses with Molecular Genetic Data

In 1994, the publication of Herrnstein's and Murray's The Bell Curve resulted in a social science maelstrom of responses. In the present study, we argue that Herrnstein's and Murray's assertions were made prematurely, on their own terms, given the lack of data available to test the role of genotype in the dynamics of achievement and attainment in U.S. society. Today, however, the scientific community has access to at least one dataset that is nationally representative and has genome-wide molecular markers. We deploy those data from the Health and Retirement Study in order to test the core series of propositions offered by Herrnstein and Murray in 1994. First, we ask whether the effect of genotype is increasing in predictive power across birth cohorts in the middle twentieth century. Second, we ask whether assortative mating on relevant genotypes is increasing across the same time period. Finally, we ask whether educational genotypes are increasingly predictive of fertility (number ever born [NEB]) in tandem with the rising (negative) association of educational outcomes and NEB. The answers to these questions are mostly no; while molecular genetic markers can predict educational attainment, we find little evidence for the proposition that we are becoming increasingly genetically stratified.

Gendering Genetics: Biological Contingencies in the Protective Effects of Social Integration for Men and Women

Evidence that social and biological processes are intertwined in producing health and human behavior is rapidly accumulating. Using a feminist approach, this research explores how gender moderates the interaction between biological processes and men's and women's behavioral and emotional responses to similar social environments. Using data from the Collaborative Study on the Genetics of Alcoholism, the influence of gender, social integration, and genetic risk on nicotine and alcohol dependence is examined. Three-way interaction models reveal gender-specific moderation of interactions between genetic risk score and social integration. Namely, being currently married and reporting positive social psychological integration are predictive of reduced risk of nicotine dependence among men with genetic susceptibility to strong nicotine cravings in the presence of social cues like stress. In contrast, the protective effects of marital status and social integration are substantially attenuated and absent, respectively, among women with high-risk genotypes. This pattern reflects the dualism (i.e., simultaneous costs and benefits) inherent in social integration for women, which may disproportionately affect those with a genetic sensitivity to stress. These findings contest the notion of genotype as static biological hardwiring that is independent from social and cultural systems of gender difference.

Genetic epidemiology of migraine and depression

Background

Migraine and major depressive disorder (commonly referred to as depression) are both common disorders with a significant impact on society. Studies in both clinical and community-based settings have demonstrated a strong relationship between migraine and depression. In addition to complicating the diagnosis, depression that is comorbid with migraine may lower treatment adherence, increase risk of medication overuse and is associated with migraine chronification, thus leading to higher direct and indirect costs and poorer health-related outcomes with increased disability.

Aim

The aim of this review is to summarise the current knowledge on the genetic epidemiology of migraine and depression and the possible biological mechanisms underlying their comorbidity.

Methods

We present a narrative review reporting on the current literature.

Results and conclusions

Epidemiological findings indicate that there is a bidirectional relationship between migraine and depression, with one disorder increasing the risk for the other and vice versa, suggesting shared biological mechanisms. Twin and family studies indicate that this bidirectional relationship can be explained, at least partly, by shared underlying genetically determined disease mechanisms. Although no genes have been robustly associated with the aetiology of both migraine and depression, genes from serotonergic, dopaminergic and GABAergic systems together with variants in the MTHFR and BDNF genes remain strong candidates.

Differential Vulnerability to Early-Life Parental Death: The Moderating Effects of Family Suicide History on Risks for Major Depression and Substance Abuse in Later Life

Only a portion of those individuals exposed to parental death in early life (PDE) develop behavioral health disorders. We utilized demographic pedigree data from the Utah Population Database to test for differential vulnerability to PDE by creating a risk score of familial susceptibility to suicide (FS) at the population level. Using logistic panel regression models, we tested for multiplicative interactions between PDE and FS on the risks of major depressive disorder (MDD) and substance abuse (SA), measured using Medicare claims, after age 65. The final sample included 155,983 individuals (born 1886-1944), yielding 1,431,060 person-years at risk (1992-2009). Net of several potential confounders, including probability of survival to age 65, we found an FS × PDE interaction for females, in which PDE and FS as main effects had no impact but jointly increased MDD risk. No statistically significant main or interactive effects were found for SA among females or for either phenotype among males. Our findings are consistent with a differential vulnerability model for MDD in females, in which early-life stress increases the risk for poor behavioral health only among the vulnerable. Furthermore, we demonstrate how demographic and pedigree data might serve as tools for investigating differential vulnerability hypotheses.

Modeling Gene-Environment Interactions With Quasi-Natural Experiments

This overview develops new empirical models that can effectively document Gene × Environment (G×E) interactions in observational data. Current G×E studies are often unable to support causal inference because they use endogenous measures of the environment or fail to adequately address the nonrandom distribution of genes across environments, confounding estimates. Comprehensive measures of genetic variation are incorporated into quasi-natural experimental designs to exploit exogenous environmental shocks or isolate variation in environmental exposure to avoid potential confounders. In addition, we offer insights from population genetics that improve upon extant approaches to address problems from population stratification. Together, these tools offer a powerful way forward for G×E research on the origin and development of social inequality across the life course.

Adolescent Loneliness and the Interaction between the Serotonin Transporter Gene (5-HTTLPR) and Parental Support: A Replication Study

Gene-by-environment interaction (GxEs) studies have gained popularity over the last decade, but the robustness of such observed interactions has been questioned. The current study contributes to this debate by replicating the only study on the interaction between the serotonin transporter gene (5-HTTLPR) and perceived parental support on adolescents’ peer-related loneliness. A total of 1,111 adolescents (51% boys) with an average age of 13.70 years (SD = 0.93) participated and three annual waves of data were collected. At baseline, adolescent-reported parental support and peer-related loneliness were assessed and genetic information was collected. Assessment of peer-related loneliness was repeated at Waves 2 and 3. Using a cohort-sequential design, a Latent Growth Curve Model was estimated. Overall, a slight increase of loneliness over time was found. However, the development of loneliness over time was found to be different for boys and girls: girls’ levels of loneliness increased over time, whereas boys’ levels of loneliness decreased. Parental support was inversely related to baseline levels of loneliness, but unrelated to change of loneliness over time. We were unable to replicate the main effect of 5-HTTLPR or the 5-HTTLPR x Support interaction effect. In the Discussion, we examine the implications of our non-replication.

Polygenic Influence on Educational Attainment: New evidence from The National Longitudinal Study of Adolescent to Adult Health

Recent studies have begun to uncover the genetic architecture of educational attainment. We build on this work using genome-wide data from siblings in the National Longitudinal Study of Adolescent to Adult Health (Add Health). We measure the genetic predisposition of siblings to educational attainment using polygenic scores. We then test how polygenic scores are related to social environments and educational outcomes. In Add Health, genetic predisposition to educational attainment is patterned across the social environment. Participants with higher polygenic scores were more likely to grow up in socially advantaged families. Even so, the previously published genetic associations appear to be causal. Among pairs of siblings, the sibling with the higher polygenic score typically went on to complete more years of schooling as compared to their lower-scored co-sibling. We found subtle differences between sibling fixed effect estimates of the genetic effect versus those based on unrelated individuals.