Genetic diversity fuels gene discovery for tobacco and alcohol use.

Tobacco and alcohol use are heritable behaviours associated with 15% and 5.3% of worldwide deaths, respectively, due largely to broad increased risk for disease and injury1-4. These substances are used across the globe, yet genome-wide association studies have focused largely on individuals of European ancestries5. Here we leveraged global genetic diversity across 3.4 million individuals from four major clines of global ancestry (approximately 21% non-European) to power the discovery and fine-mapping of genomic loci associated with tobacco and alcohol use, to inform function of these loci via ancestry-aware transcriptome-wide association studies, and to evaluate the genetic architecture and predictive power of polygenic risk within and across populations. We found that increases in sample size and genetic diversity improved locus identification and fine-mapping resolution, and that a large majority of the 3,823 associated variants (from 2,143 loci) showed consistent effect sizes across ancestry dimensions. However, polygenic risk scores developed in one ancestry performed poorly in others, highlighting the continued need to increase sample sizes of diverse ancestries to realize any potential benefit of polygenic prediction.

Examining associations between genetic and neural risk for externalizing behaviors in adolescence and early adulthood.

BACKGROUND: Researchers have identified genetic and neural risk factors for externalizing behaviors. However, it has not yet been determined if genetic liability is conferred in part through associations with more proximal neurophysiological risk markers. METHODS: Participants from the Collaborative Study on the Genetics of Alcoholism, a large, family-based study of alcohol use disorders were genotyped and polygenic scores for externalizing (EXT PGS) were calculated. Associations with target P3 amplitude from a visual oddball task (P3) and broad endorsement of externalizing behaviors (indexed via self-report of alcohol and cannabis use, and antisocial behavior) were assessed in participants of European (EA; N = 2851) and African ancestry (AA; N = 1402). Analyses were also stratified by age (adolescents, age 12-17 and young adults, age 18-32). RESULTS: The EXT PGS was significantly associated with higher levels of externalizing behaviors among EA adolescents and young adults as well as AA young adults. P3 was inversely associated with externalizing behaviors among EA young adults. EXT PGS was not significantly associated with P3 amplitude and therefore, there was no evidence that P3 amplitude indirectly accounted for the association between EXT PGS and externalizing behaviors. CONCLUSIONS: Both the EXT PGS and P3 amplitude were significantly associated with externalizing behaviors among EA young adults. However, these associations with externalizing behaviors appear to be independent of each other, suggesting that they may index different facets of externalizing.

Alcohol milestones and internalizing, externalizing, and executive function: longitudinal and polygenic score associations.

BACKGROUND: Although the link between alcohol involvement and behavioral phenotypes (e.g. impulsivity, negative affect, executive function [EF]) is well-established, the directionality of these associations, specificity to stages of alcohol involvement, and extent of shared genetic liability remain unclear. We estimate longitudinal associations between transitions among alcohol milestones, behavioral phenotypes, and indices of genetic risk. METHODS: Data came from the Collaborative Study on the Genetics of Alcoholism (n = 3681; ages 11-36). Alcohol transitions (first: drink, intoxication, alcohol use disorder [AUD] symptom, AUD diagnosis), internalizing, and externalizing phenotypes came from the Semi-Structured Assessment for the Genetics of Alcoholism. EF was measured with the Tower of London and Visual Span Tasks. Polygenic scores (PGS) were computed for alcohol-related and behavioral phenotypes. Cox models estimated associations among PGS, behavior, and alcohol milestones. RESULTS: Externalizing phenotypes (e.g. conduct disorder symptoms) were associated with future initiation and drinking problems (hazard ratio (HR)⩾1.16). Internalizing (e.g. social anxiety) was associated with hazards for progression from first drink to severe AUD (HR⩾1.55). Initiation and AUD were associated with increased hazards for later depressive symptoms and suicidal ideation (HR⩾1.38), and initiation was associated with increased hazards for future conduct symptoms (HR = 1.60). EF was not associated with alcohol transitions. Drinks per week PGS was linked with increased hazards for alcohol transitions (HR⩾1.06). Problematic alcohol use PGS increased hazards for suicidal ideation (HR = 1.20). CONCLUSIONS: Behavioral markers of addiction vulnerability precede and follow alcohol transitions, highlighting dynamic, bidirectional relationships between behavior and emerging addiction.

A Developmentally-Informative Genome-wide Association Study of Alcohol Use Frequency.

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.

Investigating genetically stratified subgroups to better understand the etiology of alcohol misuse.

Alcohol misuse (AM) is highly prevalent and harmful, with theorized subgroups differing on internalizing and externalizing dimensions. Despite known heterogeneity, genome-wide association studies (GWAS) are usually conducted on unidimensional phenotypes. These approaches have identified important genes related to AM but fail to capture a large part of the heritability, even with recent increases in sample sizes. This study aimed to address phenotypic heterogeneity in GWAS to aid gene finding and to uncover the etiology of different types of AM. Genetic and phenotypic data from 410,414 unrelated individuals of multiple ancestry groups (primarily European) in the UK Biobank were obtained. Mixture modeling was applied to measures of alcohol misuse and internalizing/externalizing psychopathology to uncover phenotypically homogenous subclasses, which were carried forward to GWAS and functional annotation. A four-class model emerged with "low risk", "internalizing-light/non-drinkers", "heavy alcohol use-low impairment", and "broad high risk" classes. SNP heritability ranged from 3 to 18% and both known AM signals and novel signals were captured by genomic risk loci. Class comparisons showed distinct patterns of regional brain tissue enrichment and genetic correlations with internalizing and externalizing phenotypes. Despite some limitations, this study demonstrated the utility of genetic research on homogenous subclasses. Not only were novel genetic signals identified that might be used for follow-up studies, but addressing phenotypic heterogeneity allows for the discovery and investigation of differential genetic vulnerabilities in the development of AM, which is an important step towards the goal of personalized medicine.

Alcohol reverses the effects of KCNJ6 (GIRK2) noncoding variants on excitability of human glutamatergic neurons.

Synonymous and noncoding single nucleotide polymorphisms (SNPs) in the KCNJ6 gene, encoding G protein-gated inwardly rectifying potassium channel subunit 2 (GIRK2), have been linked with increased electroencephalographic frontal theta event-related oscillations (ERO) in subjects diagnosed with alcohol use disorder (AUD). To identify molecular and cellular mechanisms while retaining the appropriate genetic background, we generated induced excitatory glutamatergic neurons (iN) from iPSCs derived from four AUD-diagnosed subjects with KCNJ6 variants ("Affected: AF") and four control subjects without variants ("Unaffected: UN"). Neurons were analyzed for changes in gene expression, morphology, excitability and physiological properties. Single-cell RNA sequencing suggests that KCNJ6 AF variant neurons have altered patterns of synaptic transmission and cell projection morphogenesis. Results confirm that AF neurons express lower levels of GIRK2, have greater neurite area, and elevated excitability. Interestingly, exposure to intoxicating concentrations of ethanol induces GIRK2 expression and reverses functional effects in AF neurons. Ectopic overexpression of GIRK2 alone mimics the effect of ethanol to normalize induced excitability. We conclude that KCNJ6 variants decrease GIRK2 expression and increase excitability and that this effect can be minimized or reduced with ethanol.

Genetic nurture effects for alcohol use disorder.

We tested whether aspects of the childhood/adolescent home environment mediate genetic risk for alcohol problems within families across generations. Parental relationship discord and parental divorce were the focal environments examined. The sample included participants of European ancestry (N = 4806, 51% female) and African ancestry (N = 1960, 52% female) from the high-risk Collaborative Study on the Genetics of Alcoholism. Alcohol outcomes in the child generation included lifetime criterion counts for DSM-5 Alcohol Use Disorder (AUD), lifetime maximum drinks in 24 h, age at initiation of regular drinking, and age at first alcohol intoxication. Predictors in the parent generation included relationship discord, divorce, alcohol measures parallel to those in the child generation, and polygenic scores for alcohol problems. Parental polygenic scores were partitioned into alleles that were transmitted and non-transmitted to the child. The results from structural equation models were consistent with genetic nurture effects in European ancestry families. Exposure to parental relationship discord and parental divorce mediated, in part, the transmission of genetic risk for alcohol problems from parents to children to predict earlier ages regular drinking (ßindirect = -0.018 [-0.026, -0.011]) and intoxication (ßindirect = -0.015 [-0.023, -0.008]), greater lifetime maximum drinks (ßindirect = 0.006 [0.002, 0.01]) and more lifetime AUD criteria (ßindirect = 0.011 [0.006, 0.016]). In contrast, there was no evidence that parental alleles had indirect effects on offspring alcohol outcomes via parental relationship discord or divorce in the smaller number of families of African ancestry. In conclusion, parents transmit genetic risk for alcohol problems to their children not only directly, but also indirectly via genetically influenced aspects of the home environment. Further investigation of genetic nurture in non-European samples is needed.

Mapping potential pathways from polygenic liability through brain structure to psychological problems across the transition to adolescence.

BACKGROUND: We used a polygenic score for externalizing behavior (extPGS) and structural MRI to examine potential pathways from genetic liability to conduct problems via the brain across the adolescent transition. METHODS: Three annual assessments of child conduct problems, attention-deficit/hyperactivity problems, and internalizing problems were conducted across across 9-13 years of age among 4,475 children of European ancestry in the Adolescent Brain Cognitive DevelopmentSM Study (ABCD Study®). RESULTS: The extPGS predicted conduct problems in each wave (R2 = 2.0%-2.9%). Bifactor models revealed that the extPRS predicted variance specific to conduct problems (R2 = 1.7%-2.1%), but also variance that conduct problems shared with other measured problems (R2 = .8%-1.4%). Longitudinally, extPGS predicted levels of specific conduct problems (R2 = 2.0%), but not their slope of change across age. The extPGS was associated with total gray matter volume (TGMV; R2 = .4%) and lower TGMV predicted both specific conduct problems (R2 = 1.7%-2.1%) and the variance common to all problems in each wave (R2 = 1.6%-3.1%). A modest proportion of the polygenic liability specific to conduct problems in each wave was statistically mediated by TGMV. CONCLUSIONS: Across the adolescent transition, the extPGS predicted both variance specific to conduct problems and variance shared by all measured problems. The extPGS also was associated with TGMV, which robustly predicted conduct problems. Statistical mediation analyses suggested the hypothesis that polygenic variation influences individual differences in brain development that are related to the likelihood of conduct problems during the adolescent transition, justifying new research to test this causal hypothesis.

Initial Results from a New College Substance Use Prevention Program Targeting Externalizing and Internalizing Traits.

Objective: College students engage in high rates of risky substance use. Standard college prevention strategies focus on providing feedback about current substance use behaviors and harm reduction strategies but do not address the underlying genetically-influenced risk factors impacting these behaviors. We created an online Personalized Feedback Program (PFP) for college students that targets genetically-influenced externalizing and internalizing risk pathways and provides personalized recommendations and campus resources. College students received personalized feedback on four risk domains (Sensation Seeking, Impulsivity, Extraversion, and Neuroticism). Methods: An open trial (n = 300) was conducted at a large public university in spring of 2021 to assess initial responses to the PFP and evaluate intentions related to future substance use and campus resource use. Results: 81% of students in the open trial reported they enjoyed the Personalized Feedback Program. Participants reported intending to use significantly more campus resources after completing the PFP. Among participants that drank, 39% reported they intended to decrease their alcohol consumption and 41% reported they intended to decrease the number of times they get drunk after completing the PFP; these intentions to reduce use after completing the PFP are higher than rates found in previous studies. Conclusion: Preliminary data indicate that the Personalized Feedback Program may be a complementary method to enhance current college substance use prevention programs.

Interpersonal ethnic-racial discrimination and tobacco products: The moderating role of critical action.

OBJECTIVE: The present study aimed to understand the role of critical action, sociopolitical participation, an essential form of consciousness in the relationship between interpersonal discrimination and the use of tobacco products. METHOD: The present study was part of a more extensive longitudinal study on students' genetic and environmental experiences. To examine these associations, 164 racially minoritized college students (Mage = 19.86, SD = 0.28) were surveyed for this study. RESULTS: Findings indicated that the relation between interpersonal ethnic-racial discrimination (IERD) and tobacco products was moderated by critical action. Specifically, IERD was associated with greater use of tobacco products when students had low critical consciousness-critical action. The relation between IERD and the use of tobacco products became nonsignificant when students had high critical action. CONCLUSIONS: Critical action was protective in mitigating increased tobacco use in the context of discrimination experiences. Research, clinical, and policy implications are discussed in efforts to reduce tobacco-related disparities among racially minoritized college students. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Characteristics of Students Participating in Collegiate Recovery Programs and the Impact of COVID-19: An Updated National Longitudinal Study.

The goals of the present study were to describe the development of the first national longitudinal study of collegiate recovery programs (CRP) students; provide an updated characterization of CRP students' demographics, past problem severity, and current recovery-related functioning; and examine the perceived impact of COVID-19 on CRP students' recovery. Universities and community colleges with CRPs across the United States and Ontario, Canada, were invited to partner on this project. Launched in fall 2020, three cohorts of participants were recruited. All participants who completed the baseline survey (N = 334 from 43 CRPs) were invited to complete follow-up surveys. The sample was composed of mostly undergraduate, White, cisgender women averaging 29 years old at baseline. They reported challenging backgrounds, including high levels of polysubstance use, alcohol/substance problem severity, mental health challenges, and involvement with the criminal legal system. Despite such adversity, they evidenced high levels of recovery-related functioning. Recovery capital and quality of life were high. Students reported an average of nearly four years in recovery, with most having between two and four years of abstinence from their primary substance of choice. COVID-19 represented a substantial source of stress for many, impacting some students' abstinence and recovery-related functioning. Results generally parallel findings from the only other national study of CRP students conducted a decade ago, providing a much-needed update and novel insights into CRP students. Findings can inform our understanding of the CRP student population and can be used to tailor CRP design and service offerings to students' backgrounds and needs.

Guidelines for Evaluating the Comparability of Down-Sampled GWAS Summary Statistics.

Proprietary genetic datasets are valuable for boosting the statistical power of genome-wide association studies (GWASs), but their use can restrict investigators from publicly sharing the resulting summary statistics. Although researchers can resort to sharing down-sampled versions that exclude restricted data, down-sampling reduces power and might change the genetic etiology of the phenotype being studied. These problems are further complicated when using multivariate GWAS methods, such as genomic structural equation modeling (Genomic SEM), that model genetic correlations across multiple traits. Here, we propose a systematic approach to assess the comparability of GWAS summary statistics that include versus exclude restricted data. Illustrating this approach with a multivariate GWAS of an externalizing factor, we assessed the impact of down-sampling on (1) the strength of the genetic signal in univariate GWASs, (2) the factor loadings and model fit in multivariate Genomic SEM, (3) the strength of the genetic signal at the factor level, (4) insights from gene-property analyses, (5) the pattern of genetic correlations with other traits, and (6) polygenic score analyses in independent samples. For the externalizing GWAS, although down-sampling resulted in a loss of genetic signal and fewer genome-wide significant loci; the factor loadings and model fit, gene-property analyses, genetic correlations, and polygenic score analyses were found robust. Given the importance of data sharing for the advancement of open science, we recommend that investigators who generate and share down-sampled summary statistics report these analyses as accompanying documentation to support other researchers' use of the summary statistics.

Clinical, environmental, and genetic risk factors for substance use disorders: characterizing combined effects across multiple cohorts.

Substance use disorders (SUDs) incur serious social and personal costs. The risk for SUDs is complex, with risk factors ranging from social conditions to individual genetic variation. We examined whether models that include a clinical/environmental risk index (CERI) and polygenic scores (PGS) are able to identify individuals at increased risk of SUD in young adulthood across four longitudinal cohorts for a combined sample of N = 15,134. Our analyses included participants of European (NEUR = 12,659) and African (NAFR = 2475) ancestries. SUD outcomes included: (1) alcohol dependence, (2) nicotine dependence; (3) drug dependence, and (4) any substance dependence. In the models containing the PGS and CERI, the CERI was associated with all three outcomes (ORs = 01.37-1.67). PGS for problematic alcohol use, externalizing, and smoking quantity were associated with alcohol dependence, drug dependence, and nicotine dependence, respectively (OR = 1.11-1.33). PGS for problematic alcohol use and externalizing were also associated with any substance dependence (ORs = 1.09-1.18). The full model explained 6-13% of the variance in SUDs. Those in the top 10% of CERI and PGS had relative risk ratios of 3.86-8.04 for each SUD relative to the bottom 90%. Overall, the combined measures of clinical, environmental, and genetic risk demonstrated modest ability to distinguish between affected and unaffected individuals in young adulthood. PGS were significant but added little in addition to the clinical/environmental risk index. Results from our analysis demonstrate there is still considerable work to be done before tools such as these are ready for clinical applications.

A longitudinal study examining the associations between interpersonal trauma and romantic relationships among college students.

We examined the associations between the developmental timing of interpersonal trauma exposure (IPT) and three indicators of involvement in and quality of romantic relationships in emerging adulthood: relationship status, relationship satisfaction, and partner alcohol use. We further examined whether these associations varied in a sex-specific manner. In a sample of emerging adult college students (N = 12,358; 61.5% female) assessed longitudinally across the college years, we found precollege IPT increased the likelihood of being in a relationship, while college-onset IPT decreased the likelihood. Precollege and college-onset IPT predicted lower relationship satisfaction, and college-onset IPT predicted higher partner alcohol use. There was no evidence that associations between IPT and relationship characteristics varied in a sex-specific manner. Findings indicate that IPT exposure, and the developmental timing of IPT, may affect college students' relationship status. Findings also suggest that IPT affects their ability to form satisfying relationships with prosocial partners.

Alcohol use polygenic risk score, social support, and alcohol use among European American and African American adults.

Alcohol use is influenced by genetic and environmental factors. We examined the interactive effects between genome-wide polygenic risk scores for alcohol use (alc-PRS) and social support in relation to alcohol use among European American (EA) and African American (AA) adults across sex and developmental stages (emerging adulthood, young adulthood, and middle adulthood). Data were drawn from 4,011 EA and 1,274 AA adults from the Collaborative Study on the Genetics of Alcoholism who were between ages 18-65 and had ever used alcohol. Participants completed the Semi-Structured Assessment for the Genetics of Alcoholism and provided saliva or blood samples for genotyping. Results indicated that social support from friends, but not family, moderated the association between alc-PRS and alcohol use among EAs and AAs (only in middle adulthood for AAs); alc-PRS was associated with higher levels of alcohol use when friend support was low, but not when friend support was high. Associations were similar across sex but differed across developmental stages. Findings support the important role of social support from friends in buffering genetic risk for alcohol use among EA and AA adults and highlight the need to consider developmental changes in the role of social support in relation to alcohol use.

A multivariate approach to understanding the genetic overlap between externalizing phenotypes and substance use disorders.

Substance use disorders (SUDs) are phenotypically and genetically correlated with each other and with other psychological traits characterized by behavioural under-control, termed externalizing phenotypes. In this study, we used genomic structural equation modelling to explore the shared genetic architecture among six externalizing phenotypes and four SUDs used in two previous multivariate genome-wide association studies of an externalizing and an addiction risk factor, respectively. We first evaluated five confirmatory factor analytic models, including a common factor model, alternative parameterizations of two-factor structures and a bifactor model. We next explored the genetic correlations between factors identified in these models and other relevant psychological traits. Finally, we quantified the degree of polygenic overlap between externalizing and addiction risk using MiXeR. We found that the common and two-factor structures provided the best fit to the data, evidenced by high factor loadings, good factor reliability and no evidence of concerning model characteristics. The two-factor models yielded high genetic correlations between factors (rg s ≥ 0.87), and between the effect sizes of genetic correlations with external traits (rg  ≥ 0.95). Nevertheless, 21 of the 84 correlations with external criteria showed small, significant differences between externalizing and addiction risk factors. MiXer results showed that approximately 81% of influential externalizing variants were shared with addiction risk, whereas addiction risk shared 56% of its influential variants with externalizing. These results suggest that externalizing and addiction genetic risk are largely shared, though both constructs also retain meaningful unshared genetic variance. These results can inform future efforts to identify specific genetic influences on externalizing and SUDs.

Drinking Motives, Alcohol Misuse, and Internalizing and Externalizing Psychopathology across College: A Cross-Lagged Panel Study.

Background: Drinking motives are strong proximal predictors of alcohol use behaviors and may represent a mediational mechanism by which different individual predispositions toward internalizing or externalizing psychopathology lead to the development of alcohol misuse. However, whether the association is due to a causal relationship or a shared etiology (i.e., confounding) is difficult to determine and may change across developmental periods. Methods: This study leveraged a cross-lagged panel design to disentangle the nature of the relationships between self-report measures of drinking motives, alcohol misuse, and internalizing and externalizing psychopathology in a 4-year longitudinal sample of college students (N = 9,889). Results: Results pointed to a putative causal effect of drinking motives on early binge drinking frequency, but the direction of effect later reversed, reflecting a possible developmental shift during college. On the other hand, the relationships between drinking motives and internalizing/externalizing psychopathology appeared to be driven by shared etiology rather than direct causal mechanisms. Conclusions: These findings highlight the distinct and important role of drinking motives in the etiology of alcohol misuse and have implications for the application of tailored prevention and treatment strategies.

Family History and Alcohol Use Outcomes: Examining Transmission of Risk through Impulsivity and the Moderating Role of Organized Sports Participation.

BACKGROUND: College students are at risk for alcohol misuse and those who participate in organized sports are at even higher risk. Family history of alcohol problems (FH) and impulsivity are well-documented risk factors for alcohol use outcomes, but no research has examined the role of organized sports participation in moderating these associations. This study examined the associations between FH, alcohol consumption and alcohol use disorder (AUD) symptoms, the role of UPPS-P (Urgency, Premeditation, Perseverance, Sensation Seeking, Positive Urgency impulsive behavior scale) impulsivity dimensions in mediating the association between FH and alcohol use outcomes, and whether these associations vary by students' organized sports participation. METHOD: Participants (N = 3,959, 64.7% female, 51.8% White; Mean age = 18.48 years, SD = .40) were recruited from a large, public university and completed an online survey in the fall and spring semesters of their first year in college. Path analyses were conducted in Mplus. RESULTS: FH was associated with higher levels of alcohol consumption and more AUD symptoms. Lack of premeditation, lack of perseverance, and negative urgency partially mediated the associations between FH and alcohol consumption and AUD symptoms. The association between negative urgency and AUD symptoms was stronger for organized sports participants. CONCLUSIONS: Impulsivity dimensions are risk factors for both alcohol consumption and AUD symptoms and serve as important pathways for the transmission of risk between generations. Prevention and intervention efforts aimed at reducing problematic alcohol use should target impulsivity generally, and particularly negative urgency among college students who participate in organized sports.

The impact of receiving polygenic risk scores for alcohol use disorder on psychological distress, risk perception, and intentions to reduce drinking.

For the return of polygenic risk scores to become an acceptable clinical practice in psychiatry, receipt of polygenic risk scores must be associated with minimal harm and changes in behavior that decrease one's risk for developing a psychiatric outcome. Data from a randomized controlled trial was used to assess the impact of different levels of hypothetical polygenic risk scores for alcohol use disorder on psychological distress, risk perception, and intentions to change drinking behaviors. The analytic sample consisted of 325 participants recruited from an urban, public university. Results demonstrated that there were significant increases in psychological distress as the level of genetic risk for alcohol use disorder increased. In addition, the perceived chance of developing alcohol use disorder significantly increased as the level of genetic risk increased. Promisingly, a greater proportion of participants indicated that they would intend to engage in follow-up behaviors, such as seeking additional information, talking to a healthcare provider about risk, and reducing drinking behaviors, as the level of genetic risk increased. Returning polygenic risk scores for alcohol use disorder in a clinical setting has the potential to promote risk-reducing behavior change, especially with increasing levels of genetic risk. The study was registered on ClinicalTrials.gov (Identifier: NCT05143073).

Principal Component Analysis Reduces Collider Bias in Polygenic Score Effect Size Estimation.

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.