Browsing by Author "Thomas, Nathaniel S."

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    A Developmentally-Informative Genome-wide Association Study of Alcohol Use Frequency
    (Springer, 2024) Thomas, Nathaniel S.; Gillespie, Nathan A.; Chan, Grace; Edenberg, Howard J.; Kamarajan, Chella; I-Chun Kuo, Sally; Miller, Alex P.; Nurnberger, John I., Jr.; Tischfield, Jay; Dick, Danielle M.; Salvatore, Jessica E.; Medical and Molecular Genetics, School of Medicine
    Contemporary genome-wide association study (GWAS) methods typically do not account for variability in genetic effects throughout development. We applied genomic structural equation modeling to combine developmentally-informative phenotype data and GWAS to create polygenic scores (PGS) for alcohol use frequency that are specific to developmental stage. Longitudinal cohort studies targeted for gene-identification analyses include the Collaborative Study on the Genetics of Alcoholism (adolescence n = 1,118, early adulthood n = 2,762, adulthood n = 5,255), the National Longitudinal Study of Adolescent to Adult Health (adolescence n = 3,089, early adulthood n = 3,993, adulthood n = 5,149), and the Avon Longitudinal Study of Parents and Children (ALSPAC; adolescence n = 5,382, early adulthood n = 3,613). PGS validation analyses were conducted in the COGA sample using an alternate version of the discovery analysis with COGA removed. Results suggest that genetic liability for alcohol use frequency in adolescence may be distinct from genetic liability for alcohol use frequency later in developmental periods. The age-specific PGS predicts an increase of 4 drinking days per year per PGS standard deviation when modeled separately from the common factor PGS in adulthood. The current work was underpowered at all steps of the analysis plan. Though small sample sizes and low statistical power limit the substantive conclusions that can be drawn regarding these research questions, this work provides a foundation for future genetic studies of developmental variability in the genetic underpinnings of alcohol use behaviors and genetically-informed, age-matched phenotype prediction.
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    Alcohol Use Disorder, Psychiatric Comorbidities, Marriage and Divorce in a High-risk Sample
    (American Psychological Association, 2022) Thomas, Nathaniel S.; Kuo, Sally I-Chun; Aliev, Fazil; McCutcheon, Vivia V.; Meyers, Jacquelyn M.; Chan, Grace; Hesselbrock, Victor; Kamarajan, Chella; Kinreich, Sivan; Kramer, John R.; Kuperman, Samuel; Lai, Dongbing; Plawecki, Martin H.; Porjesz, Bernice; Schuckit, Marc A.; Dick, Danielle M.; Bucholz, Kathleen K.; Salvatore, Jessica E.; Psychiatry, School of Medicine
    Objective: To examine associations between alcohol use disorder (AUD), its psychiatric comorbidities, and their interactions, with marital outcomes in a diverse high-risk, genetically informative sample. Method: Participants included European ancestry (EA; n = 4,045) and African ancestry (AA; n = 1,550) individuals from the multigenerational Collaborative Study on the Genetics of Alcoholism (COGA) sample (56% female, Mage ∼ 41 years). Outcomes were lifetime marriage and divorce. Predictors included lifetime AUD, an alcohol problems polygenic score (PRS), and AUD comorbidities, including conduct or antisocial personality disorder (ASP), cannabis dependence/abuse (CAN), frequent tobacco use (TOB), and major depressive disorder (MDD). Mixed effect Cox models and generalized linear mixed effects models were fit. Results: Among EA participants, those with AUD and CAN were less likely to marry (hazard ratios [HRs] 0.70-0.83, ps < 0.01). Among AA participants, those with AUD and TOB were less likely to marry (HRs 0.66-0.82, ps < 0.05) and those with MDD were more likely to marry (HR = 1.34, ps < 0.01). Among EA participants, AUD, CAN, TOB, and MDD were associated with higher odds of divorce (odds ratios [ORs] 1.59-2.21, ps < 0.01). Among AA participants, no predictors were significantly associated with divorce. Significant random effects indicated genetic and environmental influences on marriage, but only environmental factors on divorce. Conclusions: In a high-risk sample, AUD was associated with reduced likelihood of marriage in EA and AA individuals and increased risk of divorce in EA individuals. These associations were largely independent of comorbidities. Genetic and environmental background factors contributed to marriage, while only environmental background factors contributed to divorce.
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    Principal Component Analysis Reduces Collider Bias in Polygenic Score Effect Size Estimation
    (Springer, 2022) Thomas, Nathaniel S.; Barr, Peter; Aliev, Fazil; Stephenson, Mallory; Kuo, Sally I-Chun; Chan, Grace; Dick, Danielle M.; Edenberg, Howard J.; Hesselbrock, Victor; Kamarajan, Chella; Kuperman, Samuel; Salvatore, Jessica E.; Medical and Molecular Genetics, School of Medicine
    In this study, we test principal component analysis (PCA) of measured confounders as a method to reduce collider bias in polygenic association models. We present results from simulations and application of the method in the Collaborative Study of the Genetics of Alcoholism (COGA) sample with a polygenic score for alcohol problems, DSM-5 alcohol use disorder as the target phenotype, and two collider variables: tobacco use and educational attainment. Simulation results suggest that assumptions regarding the correlation structure and availability of measured confounders are complementary, such that meeting one assumption relaxes the other. Application of the method in COGA shows that PC covariates reduce collider bias when tobacco use is used as the collider variable. Application of this method may improve PRS effect size estimation in some cases by reducing the effect of collider bias, making efficient use of data resources that are available in many studies.