Behavior Genetics最新文献

Attention Deficit Hyperactivity Disorder (ADHD) is a common and heritable neurodevelopmental condition that has been the subject of a wealth of genetics research. Because ADHD has an early age of onset, most of this work has focused on children, meaning that less is known about the genetics of ADHD in adults. Additionally, while much research has assessed the heritability of ADHD as a general dimension, less has assessed the heritability of individual subtypes (inattention, hyperactivity) or symptoms of ADHD. It therefore remains unclear whether the genetic factors underlying ADHD symptoms conform to a unidimensional or multidimensional structure. The aim of this study was to assess the genetic and environmental dimensionality of adult ADHD symptoms. We analyzed data from 10,454 twins of the Twins Early Development Study, who provided self-reports of ADHD symptoms using the Conners scale at age 21 years. The data conformed well to a psychometric bifactor model, providing support for a general dimension of ADHD in addition to secondary dimensions for inattention and hyperactivity. However, a bifactor independent pathway twin model provided support for a general dimension only at the level of non-shared environmental effects and not additive genetic or shared environmental effects. This suggests that symptoms of ADHD cluster together under a general dimension of non-shared environmental effects, although the two subtypes of ADHD (inattention and hyperactivity) are meaningfully genetically distinct. We found the overall heritability of ADHD to be 40%, comparable with previous estimates for adult ADHD symptoms. Our results provide useful insights into the genetic and environmental architecture of specific ADHD symptoms.

Causal inference is inherently complex and relies on key assumptions that can be difficult to validate. One strong assumption is population homogeneity, which assumes that the causal direction remains consistent across individuals. However, there may be variation in causal directions across subpopulations, leading to potential heterogeneity. In psychiatry, for example, the co-occurrence of disorders such as depression and substance use disorder can arise from multiple sources, including shared genetic or environmental factors (common causes) or direct causal pathways between the disorders. A patient diagnosed with two disorders might have one recognized as primary and the other as secondary, suggesting the existence of different types of comorbidity. For example, in some individuals, depression might lead to substance use, while in others, substance use could lead to depression. We account for potential heterogeneity in causal direction by integrating the Direction of Causation (DoC) model for twin data with finite mixture modeling, which allows for the calculation of individual-level likelihoods for alternate causal directions. Through simulations, we demonstrate the effectiveness of using the Direction of Causation Twin Mixture (mixDoC) model to detect and model heterogeneity due to varying causal directions.

Education-related variables are positively associated with intelligence in both causal directions, but little is known about the associations' underlying genetically and environmentally intertwined processes and many 'third variables' are probably involved too. In this study, we investigated how school achievement, measured by grade point average (GPA), moderated intelligence test score variation in young adulthood in broadly representative samples from the U.S. state of Minnesota, Denmark, and Germany, attempting to improve both understanding of the importance of environmental contexts and the limitations of currently available modelling techniques to help remedy them. School achievement was positively associated with intelligence test scores in all three contexts, but it moderated variances differently, even within the two cohorts comprising the Minnesota sample. One Minnesota cohort and the German sample suggested that shared environmental variance was larger among individuals with extreme GPAs, while the Danish sample suggested that this was only true among individuals with low GPAs. In contrast to these observations, the other Minnesota cohort suggested that genetic and non-shared environmental variances were greater among individuals with high GPAs. These observations indicated that underlying individual developmental processes and population-level impacts differed. However, our statistical models did not capture these differences clearly. The ways in which they failed all suggested the model limitations involve an inability to address degrees to which environmental constraints restrain social movements that are confounded with individual variations in capacities to move within society.

Experimental evolution is a powerful approach to study the mechanisms underlying the adaptation of selected characters under the conditions chosen in the laboratory. Drosophila melanogaster is a species frequently used to investigate the experimental evolution of characters, especially those related to reproduction. Recent intra-generational studies showed that cis-vaccenyl acetate (cVa), a sex pheromone transferred with bacteria on eggs by females either 1 day (D1) or 5 days (D5) after copulation, differentially affected the behavior and pheromone release in adult males emerging from these eggs. Here, we extended this finding to determine whether this alternative egg exposure repeated over many generations could affect a larger set of reproduction-related characters in both sexes. To test the repetitive effects of maternal D1 or D5 post-copulatory factors, we carried out an experimental selection procedure consisting of exposing eggs during 40 successive generations to D1 or D5 maternal post-copulatory factors. We compared cVa and cuticular pheromones, courtship and mating behaviors, and fecundity at different generations in flies of D1 and D5 lines. Based on findings obtained at earlier generations, we also determined survival, bacterial composition and gene expression in adults. Some of these complex traits significantly diverged between D1 and D5 lines indicating that maternal post-copulatory factors transmitted to eggs can influence adult life history traits.

Risky sexual behavior (RSB) has been linked to externalizing problems, substance use, and, in a recent study by our lab, internalizing problems. The current study builds upon previous work investigating the relationship between RSB and internalizing problems (INT) by controlling for externalizing problems (EXT) to account for the correlation between INT and EXT. We used a twin sample from Colorado (N = 2,544) to investigate phenotypic and genetic relationships between the three latent constructs, as well as potential sex differences in those relationships. We hypothesized that the relationship between RSB and INT would be stronger for females than for males, whereas the relationship between RSB and EXT would be stronger for males than for females. We used phenotypic confirmatory factor analysis and multivariate twin analyses to address research questions. Our results show significant phenotypic relationships among RSB, INT, and EXT and provide modest evidence in males for a significant association between RSB and INT that persists when controlling for EXT, a finding which we interpret with caution. Our sex differences hypothesis was not fully supported, although the direction of effects was in the direction hypothesized for the association between RSB and INT. We discuss the complexity of RSB as a phenotype and the potential implications for public health.