AGGREGATE STABILITY AND WATER RETENTION NEAR SATURATION CHARACTERISTICS AS AFFECTED BY SOIL TEXTURE, AGGREGATE SIZE AND POLYACRYLAMIDE APPLICATION

Understanding the effects of soil intrinsic properties and extrinsic conditions on aggregate stability is essential for the development of effective soil and water conservation practices. Our objective was to evaluate the combined role of soil texture, aggregate size and application of a stabilizing agent on aggregate and structure stability indices (composite structure index [SI], the and n parameters of the VG model and the S-index) by employing the high energy (0-5.0 J kg(-1)) moisture characteristic (HEMC) method. We used aggregates of three sizes (0.25-0.5, 0.5-1.0 and 1.0-2.0 mm) from four semi-arid soils treated with polyacrylamide (PAM). An increase in SI was associated with the increase in clay content, aggregate size and PAM application. The value of increased with the increase in aggregate size and with PAM application but was not affected by soil texture. For each aggregate size, a unique exponential type relationship existed between SI and . The value of n and the S-index tended, generally, to decrease with the increase in PAM application; however, an increase in aggregate size had an inconsistent effect on these two indices. The relationship between SI and n or the S-index could not be generalized. Our results suggest that (i) the effects of PAM on aggregate stability are not trivial, and its application as a soil conservation tool should consider field soil condition, and (ii), n and S-index cannot replace the SI as a solid measure for aggregate stability and soil structure firmness when assessing soil conservation practices

Population Attributable Fraction of Early Age of Onset of Alcohol Use in Alcohol Abuse and Dependence: A 3-Year Follow-Up Study in University Students

Background: we aimed to determine the risk factors and associated population attributable fractions (PAFs) for the age of onset of alcohol use and also to identify protective factors. Methods: we analyzed follow-up data collected between autumn 2011 and spring 2016 (n = 5170) from the first two cohorts (2011, 2012) of the Spit for ScienceTM project. The dependent variables were alcohol abuse and dependence, and the independent variables were age of drinking onset, residence, ethnicity, religiosity, sexual orientation and work status. We determined the odds ratios (OR) using multilevel logistic regression for repeated measures in SPSSv.20. Results: the early onset of alcohol use was associated with an increased risk of alcohol abuse and dependence among females (OR = 14.98; OR = 11.83) and males (OR = 7.41; OR = 6.24). The PAFs for the early onset of alcohol use in alcohol abuse and dependence were respectively 80.9% and 71.7% in females and 71.0% and 63.5% in males. Among females, being white (OR = 1.58; OR = 1.51), living off-campus (OR = 1.73; OR = 2.76) and working full-time (OR = 1.69; OR = 1.78) were also risk factors. Strong religious beliefs were found to protect males from alcohol abuse (OR = 0.58), while same-gender sexual orientation increased the risk among females (OR = 2.09). Conclusion: delaying the age of onset by one year would reduce alcohol abuse among young adultsSpit for Science: The Student Survey was supported by the Virginia Commonwealth University, the NIAAA [P20 AA107828, R37AA011408, K02AA018755, and P50 AA022537] and the National Center for Research Resources and National Institutes of Health Roadmap for Medical Research [UL1RR031990]S

PRINCIPAL COMPONENTS ANALYSIS CORRECTS COLLIDER BIAS IN POLYGENIC RISK SCORE EFFECT SIZE ESTIMATION

BACKGROUND: Genome-wide polygenic scoring has emerged as a way to predict psychiatric and behavioral outcomes and identify environments that promote the expression of genetic risks. An increasing number of studies demonstrate that the effects of polygenic risk scores (PRS) may be biased by the inclusion of heritable environments as covariates when the environment is influenced by unmeasured confounding variables, an example of collider bias. Inclusion of the principal components of observed confounders as covariates may correct for the effect of unmeasured confounders. METHODS: A simulation study was conducted to test principal components analysis (PCA) as a correction for collider bias. Data were sampled from a model which tested different values for the effect of the polygenic risk score on the heritable environment, the correlation structure of the unmeasured confounding data, and the proportion of the confounding data that is used to construct the principal components. Other model parameters were fixed across all simulation iterations. RESULTS: Modeling the first PC of observed confounders as a covariate recovers the PRS effect size estimate under reasonable assumptions about the proportion of the confounding data that is measured or the correlation structure of the confounding data. Required assumptions become stricter as the effect of PRS on environment (and the magnitude of bias) increases. CONCLUSION: Inclusion of the first PC of observed confounders as a covariate may improve the accuracy of PRS effect size estimation when heritable environments are included in the model as covariates. Future directions include application of this method in observed data.https://scholarscompass.vcu.edu/gradposters/1130/thumbnail.jp

Evaluating Neighborhood, Social, and Genetic Influences on Precursors of Alcohol Use Risk Behavior in African American Adolescents

Background: Using a socioecological framework, we examined neighborhood and social stressors in concert with genetic risk for alcohol dependence in relation to externalizing behaviors, important precursors to alcohol-related problems. Methods: We used data from African American adolescents and their caregivers in the Gene, Environment, and Neighborhood Initiative, a subsample of the Mobile Youth and Poverty Study. Participants for the current analyses included 112 adolescents who reported ever having at least one full drink of alcohol. Empirical Bayes scores were used to estimate neighborhood-level violence and transitions. Multivariate models tested main effects and then interactions of family stressors, discrimination, and genetic risk with the neighborhood variables. Results: In the main effects model, adolescent externalizing behaviors were positively associated with greater family stressors, more racial discrimination experiences, and genetic liability, while neighborhood variables were nonsignificant. We found three significant interactions. Specifically, the joint effects of neighborhood violence and transitions and between these neighborhood variables and family stressors were significantly associated with externalizing behaviors. Conclusions: Our findings suggest genetic liability and complex interactions between neighborhood context and social stressors are important contributors that should be considered in the development of early prevention programs for adolescents who live in economically disadvantaged areas

Using Patterns of Genetic Association to Elucidate Shared Genetic Etiologies Across Psychiatric Disorders

Twin studies indicate that latent genetic factors overlap across comorbid psychiatric disorders. In this study, we used a novel approach to elucidate shared genetic factors across psychiatric outcomes by clustering single nucleotide polymorphisms based on their genome-wide association patterns. We applied latent profile analysis (LPA) to p-values resulting from genome-wide association studies across three phenotypes: symptom counts of alcohol dependence (AD), antisocial personality disorder (ASP), and major depression (MD), using the European–American case-control genome-wide association study subsample of the collaborative study on the genetics of alcoholism (N = 1399). In the 3-class model, classes were characterized by overall low associations (85.6% of SNPs), relatively stronger association only with MD (6.8%), and stronger associations with AD and ASP but not with MD (7.6%), respectively. These results parallel the genetic factor structure identified in twin studies. The findings suggest that applying LPA to association results across multiple disorders may be a promising approach to identify the specific genetic etiologies underlying shared genetic variance

Which adolescent factors predict alcohol misuse in young adulthood? A co-twin comparisons study

Background and aims Research on adolescent predictors of later alcohol misuse is typically conducted on samples of singletons, and associations may be confounded by between-family differences. To address potential confounding, we applied a co-twin comparison design to evaluate whether differences between co-twins in a wide array of adolescent risk factors predicted differences in young adult alcohol misuse. Design Longitudinal study in which associations between characteristics of the sample as adolescents were used to predict young adult alcohol misuse in individual-level analyses and co-twin comparisons. Setting Finland. Participants A total of 3402 individuals (1435 complete twin pairs; 36% monozygotic; 57% female) from the FinnTwin12 study. Measurements The young adult alcohol misuse outcome was a composite score of alcohol use and intoxication frequency. Adolescent predictors included factor scores representing academic performance, substance use, externalizing problems, internalizing problems, peer environment, physical health and relationship with parents; and single measures tapping alcohol expectancies, life events and pubertal development. Findings In individual-level analyses, individuals with higher adolescent substance use, externalizing problems, time with friends, peer deviance, sports involvement, sleeping difficulties, parental discipline, positive alcohol expectancies and difficulty of life events reported higher alcohol misuse in young adulthood (Ps <0.019, R-2 = 0.0003-0.0310%). Conversely, those with higher adolescent internalizing problems, parent-child relationship quality and time with parents reported lower alcohol misuse (Ps <0021, R-2 = 0.0018-0.0093%). The associations with adolescent substance use and alcohol expectancies remained significant in co-twin comparisons (Ps <0.049, R-2 = 0.0019-0.0314%). Further, academic performance emerged as a significant predictor, such that individuals with higher grades compared with their co-twin reported higher young adult alcohol misuse (Ps <0.029, R-2 = 0.0449-0.0533%). Conclusions Adolescent substance use, positive alcohol expectancies and higher academic performance appear to be robust predictors of later alcohol misuse.Peer reviewe

A Brief Critique of the TATES Procedure

The Trait-based test that uses the Extended Simes procedure (TATES) was developed as a method for conducting multivariate GWAS for correlated phenotypes whose underlying genetic architecture is complex. In this paper, we provide a brief methodological critique of the TATES method using simulated examples and a mathematical proof. Our simulated examples using correlated phenotypes show that the Type I error rate is higher than expected, and that more TATES p values fall outside of the confidence interval relative to expectation. Thus the method may result in systematic inflation when used with correlated phenotypes. In a mathematical proof we further demonstrate that the distribution of TATES p values deviates from expectation in a manner indicative of inflation. Our findings indicate the need for caution when using TATES for multivariate GWAS of correlated phenotypes

Can Genetics Predict Response to Complex Behavioral Interventions? Evidence from a Genetic Analysis of the Fast Track Randomized Control Trial

Early interventions are a preferred method for addressing behavioral problems in high-risk children, but often have only modest effects. Identifying sources of variation in intervention effects can suggest means to improve efficiency. One potential source of such variation is the genome. We conducted a genetic analysis of the Fast Track randomized control trial, a 10-year-long intervention to prevent high-risk kindergarteners from developing adult externalizing problems including substance abuse and antisocial behavior. We tested whether variants of the glucocorticoid receptor gene NR3C1 were associated with differences in response to the Fast Track intervention. We found that in European-American children, a variant of NR3C1 identified by the single-nucleotide polymorphism rs10482672 was associated with increased risk for externalizing psychopathology in control group children and decreased risk for externalizing psychopathology in intervention group children. Variation in NR3C1 measured in this study was not associated with differential intervention response in African-American children. We discuss implications for efforts to prevent externalizing problems in high-risk children and for public policy in the genomic era

Gene-by-Intervention Effects on Alcohol Dependence Symptoms in Emerging Adulthood

The Importance of Peer Influence for LGBTQ+ Youth in Rural Communities Aaron Kemmerer supported by findings from Safe as Yourself (SAY) Project Traci Wike (PI), Leah Bouchard, Maurico Yabar, and Aaron Kemmerer Objectives: To explore the experiences and narratives of LGBTQ+ youth in rural North Carolina. To elaborate on the influence of peer support and impact of peer victimization for LGBTQ+ youth in rural North Carolina. Methods: Data was collected from eleven young people who were interviewed from 2019-2020 at an LGBTQ+ youth center in rural North Carolina. The interviews were coded and analyzed using narrative analysis on a team of interraters; the team consisted of four members from VCU School of Social Work: the principle investigator, two doctoral research assistants, and an MSW research assistant. Results: Analysis of the interviews, though still in process, so far highlights the impact of the dual impact of participants’ peers --- simultaneously pointing to LGBTQ+ youth experiences with both peer victimization (as a risk factor) and peer support (as a resilience factor). Conclusions: Peer support is vital for LGBTQ+ youth in rural communities and may help offset the negative impact of peer victimization.https://scholarscompass.vcu.edu/gradposters/1059/thumbnail.jp

Predicting Alcohol Dependence Symptoms by Young Adulthood : A Co-Twin Comparisons Study

Co-twin comparisons address familial confounding by controlling for genetic and environmental influences that twin siblings share. We applied the co-twin comparison design to investigate associations of adolescent factors with alcohol dependence (AD) symptoms. Participants were 1286 individuals (581 complete twin pairs; 42% monozygotic; and 54% female) from the FinnTwin12 study. Predictors included adolescent academic achievement, substance use, externalizing problems, internalizing problems, executive functioning, peer environment, physical health, relationship with parents, alcohol expectancies, life events, and pubertal development. The outcome was lifetime AD clinical criterion count, as measured in young adulthood. We examined associations of each adolescent domain with AD symptoms in individual-level and co-twin comparison analyses. In individual-level analyses, adolescents with higher levels of substance use, teacher-reported externalizing problems at age 12, externalizing problems at age 14, self- and co-twin-reported internalizing problems, peer deviance, and perceived difficulty of life events reported more symptoms of AD in young adulthood (ps < .044). Conversely, individuals with higher academic achievement, social adjustment, self-rated health, and parent-child relationship quality met fewer AD clinical criteria (ps < .024). Associations between adolescent substance use, teacher-reported externalizing problems, co-twin-reported internalizing problems, peer deviance, self-rated health, and AD symptoms were of a similar magnitude in co-twin comparisons. We replicated many well-known adolescent correlates of later alcohol problems, including academic achievement, substance use, externalizing and internalizing problems, self-rated health, and features of the peer environment and parent-child relationship. Furthermore, we demonstrate the utility of co-twin comparisons for understanding pathways to AD. Effect sizes corresponding to the associations between adolescent substance use, teacher-reported externalizing problems, co-twin-reported internalizing problems, peer deviance, and self-rated health were not significantly attenuated (p value threshold = .05) after controlling for genetic and environmental influences that twin siblings share, highlighting these factors as candidates for further research.Peer reviewe